Objects/bytesobject.c

/* bytes object implementation */

#include "Python.h"
#include "pycore_abstract.h"      // _PyIndex_Check()
#include "pycore_bytes_methods.h" // _Py_bytes_startswith()
#include "pycore_bytesobject.h"   // _PyBytes_Find(), _PyBytes_RepeatBuffer()
#include "pycore_call.h"          // _PyObject_CallNoArgs()
#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
#include "pycore_critical_section.h" // Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST()
#include "pycore_format.h"        // F_LJUST
#include "pycore_freelist.h"      // _Py_FREELIST_FREE()
#include "pycore_global_objects.h"// _Py_GET_GLOBAL_OBJECT()
#include "pycore_initconfig.h"    // _PyStatus_OK()
#include "pycore_long.h"          // _PyLong_DigitValue
#include "pycore_list.h"          // _PyList_GetItemRef
#include "pycore_object.h"        // _PyObject_GC_TRACK
#include "pycore_pymem.h"         // PYMEM_CLEANBYTE
#include "pycore_strhex.h"        // _Py_strhex_with_sep()
#include "pycore_unicodeobject.h" // _PyUnicode_FormatLong()

#include <stddef.h>

/*[clinic input]
class bytes "PyBytesObject *" "&PyBytes_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=7a238f965d64892b]*/

#include "clinic/bytesobject.c.h"

#define PyBytesObject_SIZE _PyBytesObject_SIZE

/* Forward declaration */
static void* _PyBytesWriter_ResizeAndUpdatePointer(PyBytesWriter *writer,
                                                   Py_ssize_t size, void *data);
static Py_ssize_t _PyBytesWriter_ResizeToAllocated(PyBytesWriter *writer);


#define CHARACTERS _Py_SINGLETON(bytes_characters)
#define CHARACTER(ch) \
     ((PyBytesObject *)&(CHARACTERS[ch]))
#define EMPTY (&_Py_SINGLETON(bytes_empty))


// Return a reference to the immortal empty bytes string singleton.
static inline PyObject*
bytes_get_empty(void)
{
    PyObject *empty = &EMPTY->ob_base.ob_base;
    assert(_Py_IsImmortal(empty));
    return empty;
}


// The function cannot fail
static inline PyObject*
bytes_get_char(uint8_t ch)
{
    PyObject *obj = (PyObject*)CHARACTER(ch);
    assert(_Py_IsImmortal(obj));
    return obj;
}


static inline void
set_ob_shash(PyBytesObject *a, Py_hash_t hash)
{
_Py_COMP_DIAG_PUSH
_Py_COMP_DIAG_IGNORE_DEPR_DECLS
#ifdef Py_GIL_DISABLED
    _Py_atomic_store_ssize_relaxed(&a->ob_shash, hash);
#else
    a->ob_shash = hash;
#endif
_Py_COMP_DIAG_POP
}

// Similar to set_ob_shash() but don't use an atomic operation on Free
// Threading. This function must only be used on newly allocated bytes objects.
static inline void
set_ob_shash_unsafe(PyBytesObject *a, Py_hash_t hash)
{
    // Don't test _PyObject_IsUniquelyReferenced(), so the function can be
    // called by bytes_resize_inplace().
    assert(Py_REFCNT(a) == 1);

_Py_COMP_DIAG_PUSH
_Py_COMP_DIAG_IGNORE_DEPR_DECLS
    a->ob_shash = hash;
_Py_COMP_DIAG_POP
}

#define get_ob_shash(op) _PyBytes_GET_CACHED_HASH(op)


/*
   For PyBytes_FromString(), the parameter 'str' points to a null-terminated
   string containing exactly 'size' bytes.

   For PyBytes_FromStringAndSize(), the parameter 'str' is
   either NULL or else points to a string containing at least 'size' bytes.
   For PyBytes_FromStringAndSize(), the string in the 'str' parameter does
   not have to be null-terminated.  (Therefore it is safe to construct a
   substring by calling 'PyBytes_FromStringAndSize(origstring, substrlen)'.)
   If 'str' is NULL then PyBytes_FromStringAndSize() will allocate 'size+1'
   bytes (setting the last byte to the null terminating character) and you can
   fill in the data yourself.  If 'str' is non-NULL then the resulting
   PyBytes object must be treated as immutable and you must not fill in nor
   alter the data yourself, since the strings may be shared.

   The PyObject member 'op->ob_size', which denotes the number of "extra
   items" in a variable-size object, will contain the number of bytes
   allocated for string data, not counting the null terminating character.
   It is therefore equal to the 'size' parameter (for
   PyBytes_FromStringAndSize()) or the length of the string in the 'str'
   parameter (for PyBytes_FromString()).
*/

// Allocate a new bytes object with contents left uninitialized. The caller is
// responsible to fill the contents. size must be greater than 0.
static PyObject *
bytes_alloc(Py_ssize_t size)
{
    assert(size >= 1);

    if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
        PyErr_SetString(PyExc_OverflowError,
                        "byte string is too large");
        return NULL;
    }
    size_t alloc = PyBytesObject_SIZE + size;

    /* Inline PyObject_NewVar */
    PyBytesObject *op = (PyBytesObject *)PyObject_Malloc(alloc);
    if (op == NULL) {
        return PyErr_NoMemory();
    }

    _PyObject_InitVar(_PyVarObject_CAST(op), &PyBytes_Type, size);
    set_ob_shash_unsafe(op, -1);
    op->ob_sval[size] = '\0';
    return (PyObject *) op;
}

// Create a new bytes object with contents initialized to zero. size can be 0.
static PyObject *
_PyBytes_FromSizeZero(Py_ssize_t size)
{
    PyBytesObject *op;
    assert(size >= 0);

    if (size == 0) {
        return bytes_get_empty();
    }

    if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
        PyErr_SetString(PyExc_OverflowError,
                        "byte string is too large");
        return NULL;
    }
    size_t alloc = PyBytesObject_SIZE + size;

    /* Inline PyObject_NewVar */
    op = (PyBytesObject *)PyObject_Calloc(1, alloc);
    if (op == NULL) {
        return PyErr_NoMemory();
    }
    _PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, size);
    set_ob_shash_unsafe(op, -1);
    // op->ob_sval[size] is equal to '\0'
    return (PyObject *) op;
}

// Similar to PyBytes_FromStringAndSize(), but str must not be NULL.
static PyObject *
_PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
{
    assert(str != NULL);
    assert(size >= 0);

    if (size == 0) {
        return bytes_get_empty();
    }
    if (size == 1) {
        return bytes_get_char((uint8_t)str[0]);
    }

    PyBytesObject *op = (PyBytesObject *)bytes_alloc(size);
    if (op == NULL) {
        return NULL;
    }
    memcpy(op->ob_sval, str, size);
    return (PyObject *) op;
}

PyObject *
PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
{
    if (size < 0) {
        PyErr_SetString(PyExc_SystemError,
            "Negative size passed to PyBytes_FromStringAndSize");
        return NULL;
    }

    if (str != NULL) {
        return _PyBytes_FromStringAndSize(str, size);
    }
    else {
        if (size == 0) {
            return bytes_get_empty();
        }
        return bytes_alloc(size);
    }
}

PyObject *
PyBytes_FromString(const char *str)
{
    assert(str != NULL);
    size_t size = strlen(str);
    if (size == 0) {
        return bytes_get_empty();
    }
    if (size == 1) {
        return bytes_get_char((uint8_t)str[0]);
    }

    PyBytesObject *op = (PyBytesObject *)bytes_alloc(size);
    if (op == NULL) {
        return PyErr_NoMemory();
    }
    memcpy(op->ob_sval, str, size+1);
    return (PyObject *) op;
}


static char*
bytes_fromformat(PyBytesWriter *writer, Py_ssize_t writer_pos,
                 const char *format, va_list vargs)
{
    /* Longest 64-bit formatted numbers:
       - "18446744073709551615\0" (21 bytes)
       - "-9223372036854775808\0" (21 bytes)
       Decimal takes the most space (it isn't enough for octal.)

       Longest 64-bit pointer representation:
       "0xffffffffffffffff\0" (19 bytes).

       Longest 64-bit "%p" with "0x" prefix: len(hex(2**64-1)+'\0') = 19.
    */
    char buffer[21];

    char *s = (char*)PyBytesWriter_GetData(writer) + writer_pos;

#define WRITE_BYTES(str, len_expr) \
    do { \
        size_t _len = (len_expr); \
        size_t _prealloc = (f - p + 1); \
        if (_len > _prealloc) { \
            s = PyBytesWriter_GrowAndUpdatePointer(writer, _len - _prealloc, s); \
            if (s == NULL) { \
                return NULL; \
            } \
        } \
        memcpy(s, (str), _len); \
        s += _len; \
    } while (0)

    for (const char *f = format; *f; f++) {
        if (*f != '%') {
            *s++ = *f;
            continue;
        }

        const char *p = f++;

        /* ignore the width (ex: 10 in "%10s") */
        while (Py_ISDIGIT(*f))
            f++;

        /* parse the precision (ex: 10 in "%.10s") */
        Py_ssize_t prec = 0;
        if (*f == '.') {
            f++;
            for (; Py_ISDIGIT(*f); f++) {
                prec = (prec * 10) + (*f - '0');
            }
        }
        assert(prec >= 0);

        while (*f && *f != '%' && !Py_ISALPHA(*f)) {
            f++;
        }

        /* handle the long flag ('l'), but only for %ld and %lu.
           others can be added when necessary. */
        int longflag = 0;
        if (*f == 'l' && (f[1] == 'd' || f[1] == 'u')) {
            longflag = 1;
            ++f;
        }

        /* handle the size_t flag ('z'). */
        int size_tflag = 0;
        if (*f == 'z' && (f[1] == 'd' || f[1] == 'u')) {
            size_tflag = 1;
            ++f;
        }

        Py_ssize_t len;

        switch (*f) {
        case 'c':
        {
            int c = va_arg(vargs, int);
            if (c < 0 || c > 255) {
                PyErr_SetString(PyExc_OverflowError,
                                "PyBytes_FromFormatV(): %c format "
                                "expects an integer in range [0; 255]");
                return NULL;
            }
            *s++ = (unsigned char)c;
            break;
        }

        case 'd':
            if (longflag) {
                len = sprintf(buffer, "%ld", va_arg(vargs, long));
            }
            else if (size_tflag) {
                len = sprintf(buffer, "%zd", va_arg(vargs, Py_ssize_t));
            }
            else {
                len = sprintf(buffer, "%d", va_arg(vargs, int));
            }
            assert(1 <= len && len < (Py_ssize_t)sizeof(buffer));
            WRITE_BYTES(buffer, len);
            break;

        case 'u':
            if (longflag) {
                len = sprintf(buffer, "%lu", va_arg(vargs, unsigned long));
            }
            else if (size_tflag) {
                len = sprintf(buffer, "%zu", va_arg(vargs, size_t));
            }
            else {
                len = sprintf(buffer, "%u", va_arg(vargs, unsigned int));
            }
            assert(1 <= len && len < (Py_ssize_t)sizeof(buffer));
            WRITE_BYTES(buffer, len);
            break;

        case 'i':
            len = sprintf(buffer, "%i", va_arg(vargs, int));
            assert(1 <= len && len < (Py_ssize_t)sizeof(buffer));
            WRITE_BYTES(buffer, len);
            break;

        case 'x':
            len = sprintf(buffer, "%x", va_arg(vargs, int));
            assert(1 <= len && len < (Py_ssize_t)sizeof(buffer));
            WRITE_BYTES(buffer, len);
            break;

        case 's':
        {
            const char *str = va_arg(vargs, const char*);
            if (prec == 0) {
                len = strlen(str);
            }
            else {
                const char *end = memchr(str, 0, prec);
                if (end != NULL) {
                    len = (end - str);
                }
                else {
                    len = (size_t)prec;
                }
            }
            WRITE_BYTES(str, len);
            break;
        }

        case 'p':
            len = sprintf(buffer, "%p", va_arg(vargs, void*));
            assert(1 <= len && len < (Py_ssize_t)sizeof(buffer));
            /* %p is ill-defined:  ensure leading 0x. */
            if (buffer[1] == 'X') {
                buffer[1] = 'x';
            }
            else if (buffer[1] != 'x') {
                memmove(buffer + 2, buffer, len + 1);
                buffer[0] = '0';
                buffer[1] = 'x';
                len += 2;
            }
            WRITE_BYTES(buffer, len);
            break;

        case '%':
            *s++ = '%';
            break;

        default:
            // Invalid format string: copy unformatted string and exit.
            // No need to grow the writer buffer, we already preallocated
            // enough bytes.
            len = strlen(p);
            memcpy(s, p, len);
            s += len;
            return s;
        }
    }

    return s;

#undef WRITE_BYTES
}


PyObject *
PyBytes_FromFormatV(const char *format, va_list vargs)
{
    Py_ssize_t alloc = strlen(format);
    PyBytesWriter *writer = PyBytesWriter_Create(alloc);
    if (writer == NULL) {
        return NULL;
    }

    char *s = bytes_fromformat(writer, 0, format, vargs);
    if (s == NULL) {
        PyBytesWriter_Discard(writer);
        return NULL;
    }

    return PyBytesWriter_FinishWithPointer(writer, s);
}


PyObject *
PyBytes_FromFormat(const char *format, ...)
{
    PyObject* ret;
    va_list vargs;

    va_start(vargs, format);
    ret = PyBytes_FromFormatV(format, vargs);
    va_end(vargs);
    return ret;
}


/* Helpers for formatstring */

#define FORMAT_ERROR(EXC, FMT, ...) do {                                    \
    if (key != NULL) {                                                      \
        PyErr_Format((EXC), "format argument %R: " FMT,                     \
                     key, __VA_ARGS__);                                     \
    }                                                                       \
    else if (argidx >= 0) {                                                 \
        PyErr_Format((EXC), "format argument %zd: " FMT,                    \
                     argidx, __VA_ARGS__);                                  \
    }                                                                       \
    else {                                                                  \
        PyErr_Format((EXC), "format argument: " FMT, __VA_ARGS__);          \
    }                                                                       \
} while (0)

Py_LOCAL_INLINE(PyObject *)
getnextarg(PyObject *args, Py_ssize_t arglen, Py_ssize_t *p_argidx, int allowone)
{
    Py_ssize_t argidx = *p_argidx;
    if (argidx < arglen) {
        (*p_argidx)++;
        if (arglen >= 0) {
            return PyTuple_GetItem(args, argidx);
        }
        else if (allowone) {
            return args;
        }
    }
    PyErr_Format(PyExc_TypeError,
                 "not enough arguments for format string (got %zd)",
                 arglen < 0 ? 1 : arglen);
    return NULL;
}

/* Returns a new reference to a PyBytes object, or NULL on failure. */

static char*
formatfloat(PyObject *v, Py_ssize_t argidx, PyObject *key,
            int flags, int prec, int type,
            PyObject **p_result, PyBytesWriter *writer, char *str)
{
    char *p;
    PyObject *result;
    double x;
    size_t len;
    int dtoa_flags = 0;

    x = PyFloat_AsDouble(v);
    if (x == -1.0 && PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            FORMAT_ERROR(PyExc_TypeError,
                         "%%%c requires a real number, not %T",
                         type, v);
        }
        return NULL;
    }

    if (prec < 0)
        prec = 6;

    if (flags & F_ALT) {
        dtoa_flags |= Py_DTSF_ALT;
    }
    p = PyOS_double_to_string(x, type, prec, dtoa_flags, NULL);

    if (p == NULL)
        return NULL;

    len = strlen(p);
    if (writer != NULL) {
        str = PyBytesWriter_GrowAndUpdatePointer(writer, len, str);
        if (str == NULL) {
            PyMem_Free(p);
            return NULL;
        }
        memcpy(str, p, len);
        PyMem_Free(p);
        str += len;
        return str;
    }

    result = _PyBytes_FromStringAndSize(p, len);
    PyMem_Free(p);
    *p_result = result;
    return result != NULL ? str : NULL;
}

static PyObject *
formatlong(PyObject *v, Py_ssize_t argidx, PyObject *key,
           int flags, int prec, int type)
{
    PyObject *result, *iobj;
    if (PyLong_Check(v))
        return _PyUnicode_FormatLong(v, flags & F_ALT, prec, type);
    if (PyNumber_Check(v)) {
        /* make sure number is a type of integer for o, x, and X */
        if (type == 'o' || type == 'x' || type == 'X')
            iobj = _PyNumber_Index(v);
        else
            iobj = PyNumber_Long(v);
        if (iobj != NULL) {
            assert(PyLong_Check(iobj));
            result = _PyUnicode_FormatLong(iobj, flags & F_ALT, prec, type);
            Py_DECREF(iobj);
            return result;
        }
        if (!PyErr_ExceptionMatches(PyExc_TypeError))
            return NULL;
    }
    FORMAT_ERROR(PyExc_TypeError,
                 "%%%c requires %s, not %T",
                 type,
                 (type == 'o' || type == 'x' || type == 'X') ? "an integer"
                                                             : "a real number",
                 v);
    return NULL;
}

static int
byte_converter(PyObject *arg, Py_ssize_t argidx, PyObject *key, char *p)
{
    if (PyBytes_Check(arg)) {
        if (PyBytes_GET_SIZE(arg) != 1) {
            FORMAT_ERROR(PyExc_TypeError,
                         "%%c requires an integer in range(256) or "
                         "a single byte, not a bytes object of length %zd",
                         PyBytes_GET_SIZE(arg));
            return 0;
        }
        *p = PyBytes_AS_STRING(arg)[0];
        return 1;
    }
    else if (PyByteArray_Check(arg)) {
        if (PyByteArray_GET_SIZE(arg) != 1) {
            FORMAT_ERROR(PyExc_TypeError,
                         "%%c requires an integer in range(256) or "
                         "a single byte, not a bytearray object of length %zd",
                         PyByteArray_GET_SIZE(arg));
            return 0;
        }
        *p = PyByteArray_AS_STRING(arg)[0];
        return 1;
    }
    else if (PyIndex_Check(arg)) {
        int overflow;
        long ival = PyLong_AsLongAndOverflow(arg, &overflow);
        if (ival == -1 && PyErr_Occurred()) {
            return 0;
        }
        if (!(0 <= ival && ival <= 255)) {
            /* this includes an overflow in converting to C long */
            FORMAT_ERROR(PyExc_OverflowError,
                         "%%c argument not in range(256)%s", "");
            return 0;
        }
        *p = (char)ival;
        return 1;
    }
    FORMAT_ERROR(PyExc_TypeError,
                 "%%c requires an integer in range(256) or "
                 "a single byte, not %T",
                 arg);
    return 0;
}

static PyObject *_PyBytes_FromBuffer(PyObject *x);

static PyObject *
format_obj(PyObject *v, Py_ssize_t argidx, PyObject *key,
           const char **pbuf, Py_ssize_t *plen)
{
    PyObject *func, *result;
    /* is it a bytes object? */
    if (PyBytes_Check(v)) {
        *pbuf = PyBytes_AS_STRING(v);
        *plen = PyBytes_GET_SIZE(v);
        return Py_NewRef(v);
    }
    if (PyByteArray_Check(v)) {
        *pbuf = PyByteArray_AS_STRING(v);
        *plen = PyByteArray_GET_SIZE(v);
        return Py_NewRef(v);
    }
    /* does it support __bytes__? */
    func = _PyObject_LookupSpecial(v, &_Py_ID(__bytes__));
    if (func != NULL) {
        result = _PyObject_CallNoArgs(func);
        Py_DECREF(func);
        if (result == NULL)
            return NULL;
        if (!PyBytes_Check(result)) {
            PyErr_Format(PyExc_TypeError,
                         "%T.__bytes__() must return a bytes, not %T",
                         v, result);
            Py_DECREF(result);
            return NULL;
        }
        *pbuf = PyBytes_AS_STRING(result);
        *plen = PyBytes_GET_SIZE(result);
        return result;
    }
    else if (PyErr_Occurred()) {
        return NULL;
    }
    /* does it support buffer protocol? */
    if (PyObject_CheckBuffer(v)) {
        /* maybe we can avoid making a copy of the buffer object here? */
        result = _PyBytes_FromBuffer(v);
        if (result == NULL)
            return NULL;
        *pbuf = PyBytes_AS_STRING(result);
        *plen = PyBytes_GET_SIZE(result);
        return result;
    }
    FORMAT_ERROR(PyExc_TypeError,
                 "%%b requires a bytes-like object, "
                 "or an object that implements __bytes__, not %T",
                 v);
    return NULL;
}

/* fmt%(v1,v2,...) is roughly equivalent to sprintf(fmt, v1, v2, ...) */

PyObject *
_PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
                  PyObject *args, int use_bytearray)
{
    const char *fmt;
    Py_ssize_t arglen, argidx;
    Py_ssize_t fmtcnt;
    int args_owned = 0;
    PyObject *dict = NULL;
    PyObject *key = NULL;

    if (args == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }
    fmt = format;
    fmtcnt = format_len;

    PyBytesWriter *writer;
    if (use_bytearray) {
        writer = _PyBytesWriter_CreateByteArray(fmtcnt);
    }
    else {
        writer = PyBytesWriter_Create(fmtcnt);
    }
    if (writer == NULL) {
        return NULL;
    }
    char *res = PyBytesWriter_GetData(writer);

    if (PyTuple_Check(args)) {
        arglen = PyTuple_GET_SIZE(args);
        argidx = 0;
    }
    else {
        arglen = -1;
        argidx = -2;
    }
    if (Py_TYPE(args)->tp_as_mapping && Py_TYPE(args)->tp_as_mapping->mp_subscript &&
        !PyTuple_Check(args) && !PyBytes_Check(args) && !PyUnicode_Check(args) &&
        !PyByteArray_Check(args)) {
            dict = args;
    }

    while (--fmtcnt >= 0) {
        if (*fmt != '%') {
            Py_ssize_t len;
            char *pos;

            pos = (char *)memchr(fmt + 1, '%', fmtcnt);
            if (pos != NULL)
                len = pos - fmt;
            else
                len = fmtcnt + 1;
            assert(len != 0);

            memcpy(res, fmt, len);
            res += len;
            fmt += len;
            fmtcnt -= (len - 1);
        }
        else {
            /* Got a format specifier */
            int flags = 0;
            Py_ssize_t width = -1;
            int prec = -1;
            int c = '\0';
            int fill;
            PyObject *v = NULL;
            PyObject *temp = NULL;
            const char *pbuf = NULL;
            int sign;
            Py_ssize_t len = 0;
            char onechar; /* For byte_converter() */
            Py_ssize_t alloc;

            const char *start = fmt;
            fmt++;
            if (*fmt == '%') {
                *res++ = '%';
                fmt++;
                fmtcnt--;
                continue;
            }
            Py_CLEAR(key);
            const char *fmtstart = fmt;
            if (*fmt == '(') {
                const char *keystart;
                Py_ssize_t keylen;
                int pcount = 1;

                if (dict == NULL) {
                    PyErr_Format(PyExc_TypeError,
                                 "format requires a mapping, not %T",
                                 args);
                    goto error;
                }
                ++fmt;
                --fmtcnt;
                keystart = fmt;
                /* Skip over balanced parentheses */
                while (pcount > 0 && --fmtcnt >= 0) {
                    if (*fmt == ')')
                        --pcount;
                    else if (*fmt == '(')
                        ++pcount;
                    fmt++;
                }
                keylen = fmt - keystart - 1;
                if (fmtcnt < 0 || pcount > 0) {
                    PyErr_Format(PyExc_ValueError,
                                 "stray %% or incomplete format key "
                                 "at position %zd",
                                 (Py_ssize_t)(fmtstart - format - 1));
                    goto error;
                }
                key = _PyBytes_FromStringAndSize(keystart, keylen);
                if (key == NULL)
                    goto error;
                if (args_owned) {
                    Py_DECREF(args);
                    args_owned = 0;
                }
                args = PyObject_GetItem(dict, key);
                if (args == NULL) {
                    goto error;
                }
                args_owned = 1;
                arglen = -3;
                argidx = -4;
            }
            else {
                if (arglen < -1) {
                    PyErr_Format(PyExc_ValueError,
                                 "format requires a parenthesised mapping key "
                                 "at position %zd",
                                 (Py_ssize_t)(fmtstart - format - 1));
                    goto error;
                }
            }

            /* Parse flags. Example: "%+i" => flags=F_SIGN. */
            while (--fmtcnt >= 0) {
                switch (c = *fmt++) {
                case '-': flags |= F_LJUST; continue;
                case '+': flags |= F_SIGN; continue;
                case ' ': flags |= F_BLANK; continue;
                case '#': flags |= F_ALT; continue;
                case '0': flags |= F_ZERO; continue;
                }
                break;
            }

            /* Parse width. Example: "%10s" => width=10 */
            if (c == '*') {
                if (arglen < -1) {
                    PyErr_Format(PyExc_ValueError,
                            "* cannot be used with a parenthesised mapping key "
                            "at position %zd",
                            (Py_ssize_t)(fmtstart - format - 1));
                    goto error;
                }
                v = getnextarg(args, arglen, &argidx, 0);
                if (v == NULL)
                    goto error;
                if (!PyLong_Check(v)) {
                    FORMAT_ERROR(PyExc_TypeError, "* requires int, not %T", v);
                    goto error;
                }
                width = PyLong_AsSsize_t(v);
                if (width == -1 && PyErr_Occurred()) {
                    if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
                        FORMAT_ERROR(PyExc_OverflowError,
                                     "too big for width%s", "");
                    }
                    goto error;
                }
                if (width < 0) {
                    flags |= F_LJUST;
                    width = -width;
                }
                if (--fmtcnt >= 0)
                    c = *fmt++;
            }
            else if (c >= 0 && Py_ISDIGIT(c)) {
                width = c - '0';
                while (--fmtcnt >= 0) {
                    c = Py_CHARMASK(*fmt++);
                    if (!Py_ISDIGIT(c))
                        break;
                    if (width > (PY_SSIZE_T_MAX - ((int)c - '0')) / 10) {
                        PyErr_Format(PyExc_ValueError,
                                     "width too big at position %zd",
                                     (Py_ssize_t)(fmtstart - format - 1));
                        goto error;
                    }
                    width = width*10 + (c - '0');
                }
            }

            /* Parse precision. Example: "%.3f" => prec=3 */
            if (c == '.') {
                prec = 0;
                if (--fmtcnt >= 0)
                    c = *fmt++;
                if (c == '*') {
                    if (arglen < -1) {
                        PyErr_Format(PyExc_ValueError,
                                "* cannot be used with a parenthesised mapping key "
                                "at position %zd",
                                (Py_ssize_t)(fmtstart - format - 1));
                        goto error;
                    }
                    v = getnextarg(args, arglen, &argidx, 0);
                    if (v == NULL)
                        goto error;
                    if (!PyLong_Check(v)) {
                        FORMAT_ERROR(PyExc_TypeError,
                                     "* requires int, not %T", v);
                        goto error;
                    }
                    prec = PyLong_AsInt(v);
                    if (prec == -1 && PyErr_Occurred()) {
                        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
                            FORMAT_ERROR(PyExc_OverflowError,
                                         "too big for precision%s", "");
                        }
                        goto error;
                    }
                    if (prec < 0)
                        prec = 0;
                    if (--fmtcnt >= 0)
                        c = *fmt++;
                }
                else if (c >= 0 && Py_ISDIGIT(c)) {
                    prec = c - '0';
                    while (--fmtcnt >= 0) {
                        c = Py_CHARMASK(*fmt++);
                        if (!Py_ISDIGIT(c))
                            break;
                        if (prec > (INT_MAX - ((int)c - '0')) / 10) {
                            PyErr_Format(PyExc_ValueError,
                                "precision too big at position %zd",
                                (Py_ssize_t)(fmtstart - format - 1));
                            goto error;
                        }
                        prec = prec*10 + (c - '0');
                    }
                }
            } /* prec */
            if (fmtcnt >= 0) {
                if (c == 'h' || c == 'l' || c == 'L') {
                    if (--fmtcnt >= 0)
                        c = *fmt++;
                }
            }
            if (fmtcnt < 0) {
                PyErr_Format(PyExc_ValueError,
                             "stray %% at position %zd",
                             (Py_ssize_t)(fmtstart - format - 1));
                goto error;
            }
            v = getnextarg(args, arglen, &argidx, 1);
            if (v == NULL)
                goto error;

            if (fmtcnt == 0) {
                /* last write: disable writer overallocation */
                writer->overallocate = 0;
            }

            sign = 0;
            fill = ' ';
            switch (c) {
            case 'r':
                // %r is only for 2/3 code; 3 only code should use %a
            case 'a':
                temp = PyObject_ASCII(v);
                if (temp == NULL)
                    goto error;
                assert(PyUnicode_IS_ASCII(temp));
                pbuf = (const char *)PyUnicode_1BYTE_DATA(temp);
                len = PyUnicode_GET_LENGTH(temp);
                if (prec >= 0 && len > prec)
                    len = prec;
                break;

            case 's':
                // %s is only for 2/3 code; 3 only code should use %b
            case 'b':
                temp = format_obj(v, argidx, key, &pbuf, &len);
                if (temp == NULL)
                    goto error;
                if (prec >= 0 && len > prec)
                    len = prec;
                break;

            case 'i':
            case 'd':
            case 'u':
            case 'o':
            case 'x':
            case 'X':
                if (PyLong_CheckExact(v)
                    && width == -1 && prec == -1
                    && !(flags & (F_SIGN | F_BLANK))
                    && c != 'X')
                {
                    /* Fast path */
                    int alternate = flags & F_ALT;
                    int base;

                    switch(c)
                    {
                        default:
                            Py_UNREACHABLE();
                        case 'd':
                        case 'i':
                        case 'u':
                            base = 10;
                            break;
                        case 'o':
                            base = 8;
                            break;
                        case 'x':
                        case 'X':
                            base = 16;
                            break;
                    }

                    /* Fast path */
                    res = _PyLong_FormatBytesWriter(writer, res,
                                                    v, base, alternate);
                    if (res == NULL)
                        goto error;
                    continue;
                }

                temp = formatlong(v, argidx, key, flags, prec, c);
                if (!temp)
                    goto error;
                assert(PyUnicode_IS_ASCII(temp));
                pbuf = (const char *)PyUnicode_1BYTE_DATA(temp);
                len = PyUnicode_GET_LENGTH(temp);
                sign = 1;
                if (flags & F_ZERO)
                    fill = '0';
                break;

            case 'e':
            case 'E':
            case 'f':
            case 'F':
            case 'g':
            case 'G':
                if (width == -1 && prec == -1
                    && !(flags & (F_SIGN | F_BLANK)))
                {
                    /* Fast path */
                    res = formatfloat(v, argidx, key, flags, prec, c, NULL, writer, res);
                    if (res == NULL)
                        goto error;
                    continue;
                }

                if (!formatfloat(v, argidx, key, flags, prec, c, &temp, NULL, res))
                    goto error;
                pbuf = PyBytes_AS_STRING(temp);
                len = PyBytes_GET_SIZE(temp);
                sign = 1;
                if (flags & F_ZERO)
                    fill = '0';
                break;

            case 'c':
                pbuf = &onechar;
                len = byte_converter(v, argidx, key, &onechar);
                if (!len)
                    goto error;
                if (width == -1) {
                    /* Fast path */
                    *res++ = onechar;
                    continue;
                }
                break;

            default:
                if (Py_ISALPHA(c)) {
                    PyErr_Format(PyExc_ValueError,
                                 "unsupported format %%%c at position %zd",
                                 c, (Py_ssize_t)(fmtstart - format - 1));
                }
                else if (c == '\'') {
                    PyErr_Format(PyExc_ValueError,
                                 "stray %% at position %zd or unexpected "
                                 "format character \"'\" "
                                 "at position %zd",
                                 (Py_ssize_t)(fmtstart - format - 1),
                                 (Py_ssize_t)(fmt - format - 1));
                }
                else if (c >= 32 && c < 127 && c != '\'') {
                    PyErr_Format(PyExc_ValueError,
                                 "stray %% at position %zd or unexpected "
                                 "format character '%c' "
                                 "at position %zd",
                                 (Py_ssize_t)(fmtstart - format - 1),
                                 c, (Py_ssize_t)(fmt - format - 1));
                }
                else {
                    PyErr_Format(PyExc_ValueError,
                                 "stray %% at position %zd or unexpected "
                                 "format character with code 0x%02x "
                                 "at position %zd",
                                 (Py_ssize_t)(fmtstart - format - 1),
                                 Py_CHARMASK(c),
                                 (Py_ssize_t)(fmt - format - 1));
                }
                goto error;
            }

            if (sign) {
                if (*pbuf == '-' || *pbuf == '+') {
                    sign = *pbuf++;
                    len--;
                }
                else if (flags & F_SIGN)
                    sign = '+';
                else if (flags & F_BLANK)
                    sign = ' ';
                else
                    sign = 0;
            }
            if (width < len)
                width = len;

            alloc = width;
            if (sign != 0 && len == width)
                alloc++;
            /* size preallocated for the format */
            Py_ssize_t prealloc = fmt - start;
            if (alloc > prealloc) {
                res = PyBytesWriter_GrowAndUpdatePointer(writer, alloc - prealloc, res);
                if (res == NULL) {
                    Py_XDECREF(temp);
                    goto error;
                }
            }
#ifndef NDEBUG
            char *before = res;
#endif

            /* Write the sign if needed */
            if (sign) {
                if (fill != ' ')
                    *res++ = sign;
                if (width > len)
                    width--;
            }

            /* Write the numeric prefix for "x", "X" and "o" formats
               if the alternate form is used.
               For example, write "0x" for the "%#x" format. */
            if ((flags & F_ALT) && (c == 'o' || c == 'x' || c == 'X')) {
                assert(pbuf[0] == '0');
                assert(pbuf[1] == c);
                if (fill != ' ') {
                    *res++ = *pbuf++;
                    *res++ = *pbuf++;
                }
                width -= 2;
                if (width < 0)
                    width = 0;
                len -= 2;
            }

            /* Pad left with the fill character if needed */
            if (width > len && !(flags & F_LJUST)) {
                memset(res, fill, width - len);
                res += (width - len);
                width = len;
            }

            /* If padding with spaces: write sign if needed and/or numeric
               prefix if the alternate form is used */
            if (fill == ' ') {
                if (sign)
                    *res++ = sign;
                if ((flags & F_ALT) && (c == 'o' || c == 'x' || c == 'X')) {
                    assert(pbuf[0] == '0');
                    assert(pbuf[1] == c);
                    *res++ = *pbuf++;
                    *res++ = *pbuf++;
                }
            }

            /* Copy bytes */
            memcpy(res, pbuf, len);
            res += len;

            /* Pad right with the fill character if needed */
            if (width > len) {
                memset(res, ' ', width - len);
                res += (width - len);
            }

            if (dict && (argidx < arglen)) {
                // XXX: Never happens?
                PyErr_SetString(PyExc_TypeError,
                           "not all arguments converted during bytes formatting");
                Py_XDECREF(temp);
                goto error;
            }
            Py_XDECREF(temp);

#ifndef NDEBUG
            /* check that we computed the exact size for this write */
            assert((res - before) == alloc);
#endif
        } /* '%' */

        /* If overallocation was disabled, ensure that it was the last
           write. Otherwise, we missed an optimization */
        assert(writer->overallocate || fmtcnt == 0 || use_bytearray);
    } /* until end */

    if (argidx < arglen && !dict) {
        PyErr_Format(PyExc_TypeError,
                     "not all arguments converted during bytes formatting "
                     "(required %zd, got %zd)",
                     arglen < 0 ? 0 : argidx,
                     arglen < 0 ? 1 : arglen);
        goto error;
    }

    Py_XDECREF(key);
    if (args_owned) {
        Py_DECREF(args);
    }
    return PyBytesWriter_FinishWithPointer(writer, res);

 error:
    Py_XDECREF(key);
    PyBytesWriter_Discard(writer);
    if (args_owned) {
        Py_DECREF(args);
    }
    return NULL;
}

/* Unescape a backslash-escaped string. */
PyObject *_PyBytes_DecodeEscape2(const char *s,
                                Py_ssize_t len,
                                const char *errors,
                                int *first_invalid_escape_char,
                                const char **first_invalid_escape_ptr)
{
    PyBytesWriter *writer = PyBytesWriter_Create(len);
    if (writer == NULL) {
        return NULL;
    }
    char *p = PyBytesWriter_GetData(writer);

    *first_invalid_escape_char = -1;
    *first_invalid_escape_ptr = NULL;

    const char *end = s + len;
    while (s < end) {
        if (*s != '\\') {
            *p++ = *s++;
            continue;
        }

        s++;
        if (s == end) {
            PyErr_SetString(PyExc_ValueError,
                            "Trailing \\ in string");
            goto failed;
        }

        switch (*s++) {
        /* XXX This assumes ASCII! */
        case '\n': break;
        case '\\': *p++ = '\\'; break;
        case '\'': *p++ = '\''; break;
        case '\"': *p++ = '\"'; break;
        case 'b': *p++ = '\b'; break;
        case 'f': *p++ = '\014'; break; /* FF */
        case 't': *p++ = '\t'; break;
        case 'n': *p++ = '\n'; break;
        case 'r': *p++ = '\r'; break;
        case 'v': *p++ = '\013'; break; /* VT */
        case 'a': *p++ = '\007'; break; /* BEL, not classic C */
        case '0': case '1': case '2': case '3':
        case '4': case '5': case '6': case '7':
        {
            int c = s[-1] - '0';
            if (s < end && '0' <= *s && *s <= '7') {
                c = (c<<3) + *s++ - '0';
                if (s < end && '0' <= *s && *s <= '7')
                    c = (c<<3) + *s++ - '0';
            }
            if (c > 0377) {
                if (*first_invalid_escape_char == -1) {
                    *first_invalid_escape_char = c;
                    /* Back up 3 chars, since we've already incremented s. */
                    *first_invalid_escape_ptr = s - 3;
                }
            }
            *p++ = c;
            break;
        }
        case 'x':
            if (s+1 < end) {
                int digit1, digit2;
                digit1 = _PyLong_DigitValue[Py_CHARMASK(s[0])];
                digit2 = _PyLong_DigitValue[Py_CHARMASK(s[1])];
                if (digit1 < 16 && digit2 < 16) {
                    *p++ = (unsigned char)((digit1 << 4) + digit2);
                    s += 2;
                    break;
                }
            }
            /* invalid hexadecimal digits */

            if (!errors || strcmp(errors, "strict") == 0) {
                PyErr_Format(PyExc_ValueError,
                             "invalid \\x escape at position %zd",
                             s - 2 - (end - len));
                goto failed;
            }
            if (strcmp(errors, "replace") == 0) {
                *p++ = '?';
            } else if (strcmp(errors, "ignore") == 0)
                /* do nothing */;
            else {
                PyErr_Format(PyExc_ValueError,
                             "decoding error; unknown "
                             "error handling code: %.400s",
                             errors);
                goto failed;
            }
            /* skip \x */
            if (s < end && Py_ISXDIGIT(s[0]))
                s++; /* and a hexdigit */
            break;

        default:
            if (*first_invalid_escape_char == -1) {
                *first_invalid_escape_char = (unsigned char)s[-1];
                /* Back up one char, since we've already incremented s. */
                *first_invalid_escape_ptr = s - 1;
            }
            *p++ = '\\';
            s--;
        }
    }

    return PyBytesWriter_FinishWithPointer(writer, p);

  failed:
    PyBytesWriter_Discard(writer);
    return NULL;
}

PyObject *PyBytes_DecodeEscape(const char *s,
                                Py_ssize_t len,
                                const char *errors,
                                Py_ssize_t Py_UNUSED(unicode),
                                const char *Py_UNUSED(recode_encoding))
{
    int first_invalid_escape_char;
    const char *first_invalid_escape_ptr;
    PyObject *result = _PyBytes_DecodeEscape2(s, len, errors,
                                             &first_invalid_escape_char,
                                             &first_invalid_escape_ptr);
    if (result == NULL)
        return NULL;
    if (first_invalid_escape_char != -1) {
        if (first_invalid_escape_char > 0xff) {
            if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
                                 "b\"\\%o\" is an invalid octal escape sequence. "
                                 "Such sequences will not work in the future. ",
                                 first_invalid_escape_char) < 0)
            {
                Py_DECREF(result);
                return NULL;
            }
        }
        else {
            if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
                                 "b\"\\%c\" is an invalid escape sequence. "
                                 "Such sequences will not work in the future. ",
                                 first_invalid_escape_char) < 0)
            {
                Py_DECREF(result);
                return NULL;
            }
        }
    }
    return result;
}
/* -------------------------------------------------------------------- */
/* object api */

Py_ssize_t
PyBytes_Size(PyObject *op)
{
    if (!PyBytes_Check(op)) {
        PyErr_Format(PyExc_TypeError,
             "expected bytes, %.200s found", Py_TYPE(op)->tp_name);
        return -1;
    }
    return Py_SIZE(op);
}

char *
PyBytes_AsString(PyObject *op)
{
    if (!PyBytes_Check(op)) {
        PyErr_Format(PyExc_TypeError,
             "expected bytes, %.200s found", Py_TYPE(op)->tp_name);
        return NULL;
    }
    return ((PyBytesObject *)op)->ob_sval;
}

int
PyBytes_AsStringAndSize(PyObject *obj,
                         char **s,
                         Py_ssize_t *len)
{
    if (s == NULL) {
        PyErr_BadInternalCall();
        return -1;
    }

    if (!PyBytes_Check(obj)) {
        PyErr_Format(PyExc_TypeError,
             "expected bytes, %.200s found", Py_TYPE(obj)->tp_name);
        return -1;
    }

    *s = PyBytes_AS_STRING(obj);
    if (len != NULL)
        *len = PyBytes_GET_SIZE(obj);
    else if (strlen(*s) != (size_t)PyBytes_GET_SIZE(obj)) {
        PyErr_SetString(PyExc_ValueError,
                        "embedded null byte");
        return -1;
    }
    return 0;
}

/* -------------------------------------------------------------------- */
/* Methods */

#define STRINGLIB_GET_EMPTY() bytes_get_empty()

#include "stringlib/stringdefs.h"
#define STRINGLIB_MUTABLE 0

#include "stringlib/fastsearch.h"
#include "stringlib/count.h"
#include "stringlib/find.h"
#include "stringlib/join.h"
#include "stringlib/partition.h"
#include "stringlib/split.h"
#include "stringlib/ctype.h"

#include "stringlib/transmogrify.h"

#undef STRINGLIB_GET_EMPTY

Py_ssize_t
_PyBytes_Find(const char *haystack, Py_ssize_t len_haystack,
              const char *needle, Py_ssize_t len_needle,
              Py_ssize_t offset)
{
    assert(len_haystack >= 0);
    assert(len_needle >= 0);
    // Extra checks because stringlib_find accesses haystack[len_haystack].
    if (len_needle == 0) {
        return offset;
    }
    if (len_needle > len_haystack) {
        return -1;
    }
    assert(len_haystack >= 1);
    Py_ssize_t res = stringlib_find(haystack, len_haystack - 1,
                                    needle, len_needle, offset);
    if (res == -1) {
        Py_ssize_t last_align = len_haystack - len_needle;
        if (memcmp(haystack + last_align, needle, len_needle) == 0) {
            return offset + last_align;
        }
    }
    return res;
}

Py_ssize_t
_PyBytes_ReverseFind(const char *haystack, Py_ssize_t len_haystack,
                     const char *needle, Py_ssize_t len_needle,
                     Py_ssize_t offset)
{
    return stringlib_rfind(haystack, len_haystack,
                           needle, len_needle, offset);
}

PyObject *
PyBytes_Repr(PyObject *obj, int smartquotes)
{
    return _Py_bytes_repr(PyBytes_AS_STRING(obj), PyBytes_GET_SIZE(obj),
                          smartquotes, "bytes");
}

PyObject *
_Py_bytes_repr(const char *data, Py_ssize_t length, int smartquotes,
               const char *classname)
{
    Py_ssize_t i;
    Py_ssize_t newsize, squotes, dquotes;
    PyObject *v;
    unsigned char quote;
    Py_UCS1 *p;

    /* Compute size of output string */
    squotes = dquotes = 0;
    newsize = 3; /* b'' */
    for (i = 0; i < length; i++) {
        unsigned char c = data[i];
        Py_ssize_t incr = 1;
        switch(c) {
        case '\'': squotes++; break;
        case '"':  dquotes++; break;
        case '\\': case '\t': case '\n': case '\r':
            incr = 2; break; /* \C */
        default:
            if (c < ' ' || c >= 0x7f)
                incr = 4; /* \xHH */
        }
        if (newsize > PY_SSIZE_T_MAX - incr)
            goto overflow;
        newsize += incr;
    }
    quote = '\'';
    if (smartquotes && squotes && !dquotes)
        quote = '"';
    if (squotes && quote == '\'') {
        if (newsize > PY_SSIZE_T_MAX - squotes)
            goto overflow;
        newsize += squotes;
    }

    v = PyUnicode_New(newsize, 127);
    if (v == NULL) {
        return NULL;
    }
    p = PyUnicode_1BYTE_DATA(v);

    *p++ = 'b', *p++ = quote;
    for (i = 0; i < length; i++) {
        unsigned char c = data[i];
        if (c == quote || c == '\\')
            *p++ = '\\', *p++ = c;
        else if (c == '\t')
            *p++ = '\\', *p++ = 't';
        else if (c == '\n')
            *p++ = '\\', *p++ = 'n';
        else if (c == '\r')
            *p++ = '\\', *p++ = 'r';
        else if (c < ' ' || c >= 0x7f) {
            *p++ = '\\';
            *p++ = 'x';
            *p++ = Py_hexdigits[(c & 0xf0) >> 4];
            *p++ = Py_hexdigits[c & 0xf];
        }
        else
            *p++ = c;
    }
    *p++ = quote;
    assert(_PyUnicode_CheckConsistency(v, 1));
    return v;

  overflow:
    PyErr_Format(PyExc_OverflowError,
                 "%s object is too large to make repr", classname);
    return NULL;
}

static PyObject *
bytes_repr(PyObject *op)
{
    return PyBytes_Repr(op, 1);
}

static PyObject *
bytes_str(PyObject *op)
{
    if (_Py_GetConfig()->bytes_warning) {
        if (PyErr_WarnEx(PyExc_BytesWarning,
                         "str() on a bytes instance", 1)) {
            return NULL;
        }
    }
    return bytes_repr(op);
}

static Py_ssize_t
bytes_length(PyObject *self)
{
    PyBytesObject *a = _PyBytes_CAST(self);
    return Py_SIZE(a);
}

/* This is also used by PyBytes_Concat() and the specializing interpreter. */
PyObject *
_PyBytes_Concat(PyObject *a, PyObject *b)
{
    Py_buffer va, vb;
    PyObject *result = NULL;

    va.len = -1;
    vb.len = -1;
    if (PyObject_GetBuffer(a, &va, PyBUF_SIMPLE) != 0 ||
        PyObject_GetBuffer(b, &vb, PyBUF_SIMPLE) != 0) {
        PyErr_Format(PyExc_TypeError, "can't concat %.100s to %.100s",
                     Py_TYPE(b)->tp_name, Py_TYPE(a)->tp_name);
        goto done;
    }

    /* Optimize end cases */
    if (va.len == 0 && PyBytes_CheckExact(b)) {
        result = Py_NewRef(b);
        goto done;
    }
    if (vb.len == 0 && PyBytes_CheckExact(a)) {
        result = Py_NewRef(a);
        goto done;
    }

    if (va.len > PY_SSIZE_T_MAX - vb.len) {
        PyErr_NoMemory();
        goto done;
    }

    if ((va.len + vb.len) != 0) {
        result = bytes_alloc(va.len + vb.len);
        if (result != NULL) {
            memcpy(PyBytes_AS_STRING(result), va.buf, va.len);
            memcpy(PyBytes_AS_STRING(result) + va.len, vb.buf, vb.len);
        }
    }
    else {
        result = bytes_get_empty();
    }

  done:
    if (va.len != -1)
        PyBuffer_Release(&va);
    if (vb.len != -1)
        PyBuffer_Release(&vb);
    return result;
}

PyObject *
_PyBytes_Repeat(PyObject *self, Py_ssize_t n)
{
    PyBytesObject *a = _PyBytes_CAST(self);
    if (n < 0)
        n = 0;
    /* watch out for overflows:  the size can overflow int,
     * and the # of bytes needed can overflow size_t
     */
    if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n) {
        PyErr_SetString(PyExc_OverflowError,
            "repeated bytes are too long");
        return NULL;
    }
    Py_ssize_t old_size = Py_SIZE(a);
    Py_ssize_t new_size = old_size * n;
    if (new_size == old_size && PyBytes_CheckExact(a)) {
        return Py_NewRef(a);
    }

    if (new_size == 0) {
        return bytes_get_empty();
    }

    PyBytesObject *op = (PyBytesObject *)bytes_alloc(new_size);
    if (op == NULL) {
        return PyErr_NoMemory();
    }

    _PyBytes_RepeatBuffer(op->ob_sval, new_size, a->ob_sval, old_size);
    return (PyObject *) op;
}

static int
bytes_contains(PyObject *self, PyObject *arg)
{
    return _Py_bytes_contains(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self), arg);
}

static PyObject *
bytes_item(PyObject *self, Py_ssize_t i)
{
    PyBytesObject *a = _PyBytes_CAST(self);
    if (i < 0 || i >= Py_SIZE(a)) {
        PyErr_SetString(PyExc_IndexError, "index out of range");
        return NULL;
    }
    return _PyLong_FromUnsignedChar((unsigned char)a->ob_sval[i]);
}

static int
bytes_compare_eq(PyBytesObject *a, PyBytesObject *b)
{
    int cmp;
    Py_ssize_t len;

    len = Py_SIZE(a);
    if (Py_SIZE(b) != len)
        return 0;

    if (a->ob_sval[0] != b->ob_sval[0])
        return 0;

    cmp = memcmp(a->ob_sval, b->ob_sval, len);
    return (cmp == 0);
}

static PyObject*
bytes_richcompare(PyObject *aa, PyObject *bb, int op)
{
    /* Make sure both arguments are strings. */
    if (!(PyBytes_Check(aa) && PyBytes_Check(bb))) {
        if (_Py_GetConfig()->bytes_warning && (op == Py_EQ || op == Py_NE)) {
            if (PyUnicode_Check(aa) || PyUnicode_Check(bb)) {
                if (PyErr_WarnEx(PyExc_BytesWarning,
                                 "Comparison between bytes and string", 1))
                    return NULL;
            }
            if (PyLong_Check(aa) || PyLong_Check(bb)) {
                if (PyErr_WarnEx(PyExc_BytesWarning,
                                 "Comparison between bytes and int", 1))
                    return NULL;
            }
        }
        Py_RETURN_NOTIMPLEMENTED;
    }

    PyBytesObject *a = _PyBytes_CAST(aa);
    PyBytesObject *b = _PyBytes_CAST(bb);
    if (a == b) {
        switch (op) {
        case Py_EQ:
        case Py_LE:
        case Py_GE:
            /* a byte string is equal to itself */
            Py_RETURN_TRUE;
        case Py_NE:
        case Py_LT:
        case Py_GT:
            Py_RETURN_FALSE;
        default:
            PyErr_BadArgument();
            return NULL;
        }
    }
    else if (op == Py_EQ || op == Py_NE) {
        int eq = bytes_compare_eq(a, b);
        eq ^= (op == Py_NE);
        return PyBool_FromLong(eq);
    }
    else {
        Py_ssize_t len_a = Py_SIZE(a);
        Py_ssize_t len_b = Py_SIZE(b);
        Py_ssize_t min_len = Py_MIN(len_a, len_b);
        int c;
        if (min_len > 0) {
            c = Py_CHARMASK(*a->ob_sval) - Py_CHARMASK(*b->ob_sval);
            if (c == 0)
                c = memcmp(a->ob_sval, b->ob_sval, min_len);
        }
        else {
            c = 0;
        }
        if (c != 0) {
            Py_RETURN_RICHCOMPARE(c, 0, op);
        }
        Py_RETURN_RICHCOMPARE(len_a, len_b, op);
    }
}

static Py_hash_t
bytes_hash(PyObject *self)
{
    PyBytesObject *a = _PyBytes_CAST(self);
    Py_hash_t hash = get_ob_shash(a);
    if (hash == -1) {
        /* Can't fail */
        hash = Py_HashBuffer(a->ob_sval, Py_SIZE(a));
        set_ob_shash(a, hash);
    }
    return hash;
}

static PyObject*
bytes_subscript(PyObject *op, PyObject* item)
{
    PyBytesObject *self = _PyBytes_CAST(op);
    if (_PyIndex_Check(item)) {
        Py_ssize_t i = PyNumber_AsSsize_t(item, PyExc_IndexError);
        if (i == -1 && PyErr_Occurred())
            return NULL;
        if (i < 0)
            i += PyBytes_GET_SIZE(self);
        if (i < 0 || i >= PyBytes_GET_SIZE(self)) {
            PyErr_SetString(PyExc_IndexError,
                            "index out of range");
            return NULL;
        }
        return _PyLong_FromUnsignedChar((unsigned char)self->ob_sval[i]);
    }
    else if (PySlice_Check(item)) {
        Py_ssize_t start, stop, step, slicelength, i;
        size_t cur;
        const char* source_buf;
        char* result_buf;

        if (PySlice_Unpack(item, &start, &stop, &step) < 0) {
            return NULL;
        }
        slicelength = PySlice_AdjustIndices(PyBytes_GET_SIZE(self), &start,
                                            &stop, step);

        if (slicelength <= 0) {
            return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
        }
        else if (start == 0 && step == 1 &&
                 slicelength == PyBytes_GET_SIZE(self) &&
                 PyBytes_CheckExact(self)) {
            return Py_NewRef(self);
        }
        else if (step == 1) {
            return _PyBytes_FromStringAndSize(
                PyBytes_AS_STRING(self) + start,
                slicelength);
        }
        else {
            source_buf = PyBytes_AS_STRING(self);
            PyObject* result = bytes_alloc(slicelength);
            if (result == NULL) {
                return NULL;
            }

            result_buf = PyBytes_AS_STRING(result);
            for (cur = start, i = 0; i < slicelength;
                 cur += step, i++) {
                result_buf[i] = source_buf[cur];
            }
            return result;
        }
    }
    else {
        PyErr_Format(PyExc_TypeError,
                     "byte indices must be integers or slices, not %.200s",
                     Py_TYPE(item)->tp_name);
        return NULL;
    }
}

static int
bytes_buffer_getbuffer(PyObject *op, Py_buffer *view, int flags)
{
    PyBytesObject *self = _PyBytes_CAST(op);
    return PyBuffer_FillInfo(view, (PyObject*)self, (void *)self->ob_sval, Py_SIZE(self),
                             1, flags);
}

static PySequenceMethods bytes_as_sequence = {
    bytes_length,       /*sq_length*/
    _PyBytes_Concat,       /*sq_concat*/
    _PyBytes_Repeat,    /*sq_repeat*/
    bytes_item,         /*sq_item*/
    0,                  /*sq_slice*/
    0,                  /*sq_ass_item*/
    0,                  /*sq_ass_slice*/
    bytes_contains      /*sq_contains*/
};

static PyMappingMethods bytes_as_mapping = {
    bytes_length,
    bytes_subscript,
    0,
};

static PyBufferProcs bytes_as_buffer = {
    bytes_buffer_getbuffer,
    NULL,
};


/*[clinic input]
bytes.__bytes__
Convert this value to exact type bytes.
[clinic start generated code]*/

static PyObject *
bytes___bytes___impl(PyBytesObject *self)
/*[clinic end generated code: output=63a306a9bc0caac5 input=34ec5ddba98bd6bb]*/
{
    if (PyBytes_CheckExact(self)) {
        return Py_NewRef(self);
    }
    else {
        return _PyBytes_FromStringAndSize(self->ob_sval, Py_SIZE(self));
    }
}


#define LEFTSTRIP 0
#define RIGHTSTRIP 1
#define BOTHSTRIP 2

/*[clinic input]
@permit_long_summary
bytes.split

    sep: object = None
        The delimiter according which to split the bytes.
        None (the default value) means split on ASCII whitespace
        characters (space, tab, return, newline, formfeed, vertical tab).
    maxsplit: Py_ssize_t = -1
        Maximum number of splits to do.
        -1 (the default value) means no limit.

Return a list of the sections in the bytes, using sep as the delimiter.
[clinic start generated code]*/

static PyObject *
bytes_split_impl(PyBytesObject *self, PyObject *sep, Py_ssize_t maxsplit)
/*[clinic end generated code: output=52126b5844c1d8ef input=330ff95d92544b05]*/
{
    Py_ssize_t len = PyBytes_GET_SIZE(self), n;
    const char *s = PyBytes_AS_STRING(self), *sub;
    Py_buffer vsub;
    PyObject *list;

    if (maxsplit < 0)
        maxsplit = PY_SSIZE_T_MAX;
    if (sep == Py_None)
        return stringlib_split_whitespace((PyObject*) self, s, len, maxsplit);
    if (PyObject_GetBuffer(sep, &vsub, PyBUF_SIMPLE) != 0)
        return NULL;
    sub = vsub.buf;
    n = vsub.len;

    list = stringlib_split((PyObject*) self, s, len, sub, n, maxsplit);
    PyBuffer_Release(&vsub);
    return list;
}

/*[clinic input]
bytes.partition

    sep: Py_buffer
    /

Partition the bytes into three parts using the given separator.

This will search for the separator sep in the bytes.  If the
separator is found, returns a 3-tuple containing the part before the
separator, the separator itself, and the part after it.

If the separator is not found, returns a 3-tuple containing the
original bytes object and two empty bytes objects.
[clinic start generated code]*/

static PyObject *
bytes_partition_impl(PyBytesObject *self, Py_buffer *sep)
/*[clinic end generated code: output=f532b392a17ff695 input=2e6e551ea4f8b95a]*/
{
    return stringlib_partition(
        (PyObject*) self,
        PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
        sep->obj, (const char *)sep->buf, sep->len
        );
}

/*[clinic input]
bytes.rpartition

    sep: Py_buffer
    /

Partition the bytes into three parts using the given separator.

This will search for the separator sep in the bytes, starting at the
end.  If the separator is found, returns a 3-tuple containing the
part before the separator, the separator itself, and the part after
it.

If the separator is not found, returns a 3-tuple containing two
empty bytes objects and the original bytes object.
[clinic start generated code]*/

static PyObject *
bytes_rpartition_impl(PyBytesObject *self, Py_buffer *sep)
/*[clinic end generated code: output=191b114cbb028e50 input=f7d24f722a5470a4]*/
{
    return stringlib_rpartition(
        (PyObject*) self,
        PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
        sep->obj, (const char *)sep->buf, sep->len
        );
}

/*[clinic input]
@permit_long_summary
bytes.rsplit = bytes.split

Return a list of the sections in the bytes, using sep as the delimiter.

Splitting is done starting at the end of the bytes and working to
the front.
[clinic start generated code]*/

static PyObject *
bytes_rsplit_impl(PyBytesObject *self, PyObject *sep, Py_ssize_t maxsplit)
/*[clinic end generated code: output=ba698d9ea01e1c8f input=ba9bee56285f43e4]*/
{
    Py_ssize_t len = PyBytes_GET_SIZE(self), n;
    const char *s = PyBytes_AS_STRING(self), *sub;
    Py_buffer vsub;
    PyObject *list;

    if (maxsplit < 0)
        maxsplit = PY_SSIZE_T_MAX;
    if (sep == Py_None)
        return stringlib_rsplit_whitespace((PyObject*) self, s, len, maxsplit);
    if (PyObject_GetBuffer(sep, &vsub, PyBUF_SIMPLE) != 0)
        return NULL;
    sub = vsub.buf;
    n = vsub.len;

    list = stringlib_rsplit((PyObject*) self, s, len, sub, n, maxsplit);
    PyBuffer_Release(&vsub);
    return list;
}


/*[clinic input]
bytes.join

    iterable_of_bytes: object
    /

Concatenate any number of bytes objects.

The bytes whose method is called is inserted in between each pair.

The result is returned as a new bytes object.

Example: b'.'.join([b'ab', b'pq', b'rs']) -> b'ab.pq.rs'.
[clinic start generated code]*/

static PyObject *
bytes_join_impl(PyBytesObject *self, PyObject *iterable_of_bytes)
/*[clinic end generated code: output=0687abb94d7d438e input=7fe377b95bd549d2]*/
{
    return stringlib_bytes_join((PyObject*)self, iterable_of_bytes);
}

PyObject *
PyBytes_Join(PyObject *sep, PyObject *iterable)
{
    if (sep == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }
    if (!PyBytes_Check(sep)) {
        PyErr_Format(PyExc_TypeError,
                     "sep: expected bytes, got %T", sep);
        return NULL;
    }

    return stringlib_bytes_join(sep, iterable);
}

/*[clinic input]
@permit_long_summary
@text_signature "($self, sub[, start[, end]], /)"
bytes.find

    sub: object
    start: slice_index(accept={int, NoneType}, c_default='0') = None
         Optional start position. Default: start of the bytes.
    end: slice_index(accept={int, NoneType}, c_default='PY_SSIZE_T_MAX') = None
         Optional stop position. Default: end of the bytes.
    /

Return the lowest index in B where subsection 'sub' is found, such that 'sub' is contained within B[start,end].

Return -1 on failure.
[clinic start generated code]*/

static PyObject *
bytes_find_impl(PyBytesObject *self, PyObject *sub, Py_ssize_t start,
                Py_ssize_t end)
/*[clinic end generated code: output=d5961a1c77b472a1 input=47d0929adafc6b0b]*/
{
    return _Py_bytes_find(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                          sub, start, end);
}

/*[clinic input]
@permit_long_summary
bytes.index = bytes.find

Return the lowest index in B where subsection 'sub' is found, such that 'sub' is contained within B[start,end].

Raise ValueError if the subsection is not found.
[clinic start generated code]*/

static PyObject *
bytes_index_impl(PyBytesObject *self, PyObject *sub, Py_ssize_t start,
                 Py_ssize_t end)
/*[clinic end generated code: output=0da25cc74683ba42 input=1cb45ce71456a269]*/
{
    return _Py_bytes_index(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                           sub, start, end);
}

/*[clinic input]
@permit_long_summary
bytes.rfind = bytes.find

Return the highest index in B where subsection 'sub' is found, such that 'sub' is contained within B[start,end].

Return -1 on failure.
[clinic start generated code]*/

static PyObject *
bytes_rfind_impl(PyBytesObject *self, PyObject *sub, Py_ssize_t start,
                 Py_ssize_t end)
/*[clinic end generated code: output=51b60fa4ad011c09 input=c9473d714251f1ab]*/
{
    return _Py_bytes_rfind(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                           sub, start, end);
}

/*[clinic input]
@permit_long_summary
bytes.rindex = bytes.find

Return the highest index in B where subsection 'sub' is found, such that 'sub' is contained within B[start,end].

Raise ValueError if the subsection is not found.
[clinic start generated code]*/

static PyObject *
bytes_rindex_impl(PyBytesObject *self, PyObject *sub, Py_ssize_t start,
                  Py_ssize_t end)
/*[clinic end generated code: output=42bf674e0a0aabf6 input=bb5f473c64610c43]*/
{
    return _Py_bytes_rindex(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                            sub, start, end);
}


Py_LOCAL_INLINE(PyObject *)
do_xstrip(PyBytesObject *self, int striptype, PyObject *sepobj)
{
    Py_buffer vsep;
    const char *s = PyBytes_AS_STRING(self);
    Py_ssize_t len = PyBytes_GET_SIZE(self);
    char *sep;
    Py_ssize_t seplen;
    Py_ssize_t i, j;

    if (PyObject_GetBuffer(sepobj, &vsep, PyBUF_SIMPLE) != 0)
        return NULL;
    sep = vsep.buf;
    seplen = vsep.len;

    i = 0;
    if (striptype != RIGHTSTRIP) {
        while (i < len && memchr(sep, Py_CHARMASK(s[i]), seplen)) {
            i++;
        }
    }

    j = len;
    if (striptype != LEFTSTRIP) {
        do {
            j--;
        } while (j >= i && memchr(sep, Py_CHARMASK(s[j]), seplen));
        j++;
    }

    PyBuffer_Release(&vsep);

    if (i == 0 && j == len && PyBytes_CheckExact(self)) {
        return Py_NewRef(self);
    }
    else
        return _PyBytes_FromStringAndSize(s+i, j-i);
}


Py_LOCAL_INLINE(PyObject *)
do_strip(PyBytesObject *self, int striptype)
{
    const char *s = PyBytes_AS_STRING(self);
    Py_ssize_t len = PyBytes_GET_SIZE(self), i, j;

    i = 0;
    if (striptype != RIGHTSTRIP) {
        while (i < len && Py_ISSPACE(s[i])) {
            i++;
        }
    }

    j = len;
    if (striptype != LEFTSTRIP) {
        do {
            j--;
        } while (j >= i && Py_ISSPACE(s[j]));
        j++;
    }

    if (i == 0 && j == len && PyBytes_CheckExact(self)) {
        return Py_NewRef(self);
    }
    else
        return _PyBytes_FromStringAndSize(s+i, j-i);
}


Py_LOCAL_INLINE(PyObject *)
do_argstrip(PyBytesObject *self, int striptype, PyObject *bytes)
{
    if (bytes != Py_None) {
        return do_xstrip(self, striptype, bytes);
    }
    return do_strip(self, striptype);
}

/*[clinic input]
bytes.strip

    bytes: object = None
    /

Strip leading and trailing bytes contained in the argument.

If the argument is omitted or None, strip leading and trailing ASCII
whitespace.
[clinic start generated code]*/

static PyObject *
bytes_strip_impl(PyBytesObject *self, PyObject *bytes)
/*[clinic end generated code: output=c7c228d3bd104a1b input=9ffea5f752032bd0]*/
{
    return do_argstrip(self, BOTHSTRIP, bytes);
}

/*[clinic input]
bytes.lstrip

    bytes: object = None
    /

Strip leading bytes contained in the argument.

If the argument is omitted or None, strip leading  ASCII whitespace.
[clinic start generated code]*/

static PyObject *
bytes_lstrip_impl(PyBytesObject *self, PyObject *bytes)
/*[clinic end generated code: output=28602e586f524e82 input=9baff4398c3f6857]*/
{
    return do_argstrip(self, LEFTSTRIP, bytes);
}

/*[clinic input]
bytes.rstrip

    bytes: object = None
    /

Strip trailing bytes contained in the argument.

If the argument is omitted or None, strip trailing ASCII whitespace.
[clinic start generated code]*/

static PyObject *
bytes_rstrip_impl(PyBytesObject *self, PyObject *bytes)
/*[clinic end generated code: output=547e3815c95447da input=b78af445c727e32b]*/
{
    return do_argstrip(self, RIGHTSTRIP, bytes);
}


/*[clinic input]
@permit_long_summary
bytes.count = bytes.find

Return the number of non-overlapping occurrences of subsection 'sub' in bytes B[start:end].
[clinic start generated code]*/

static PyObject *
bytes_count_impl(PyBytesObject *self, PyObject *sub, Py_ssize_t start,
                 Py_ssize_t end)
/*[clinic end generated code: output=9848140b9be17d0f input=bb2f136f83f0d30e]*/
{
    return _Py_bytes_count(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                           sub, start, end);
}


/*[clinic input]
@permit_long_summary
bytes.translate

    table: object
        Translation table, which must be a bytes object of length 256.
    /
    delete as deletechars: object(c_default="NULL") = b''

Return a copy with each character mapped by the given translation table.

All characters occurring in the optional argument delete are
removed.  The remaining characters are mapped through the given
translation table.
[clinic start generated code]*/

static PyObject *
bytes_translate_impl(PyBytesObject *self, PyObject *table,
                     PyObject *deletechars)
/*[clinic end generated code: output=43be3437f1956211 input=bddcdef0a87895d2]*/
{
    const char *input;
    char *output;
    Py_buffer table_view = {NULL, NULL};
    Py_buffer del_table_view = {NULL, NULL};
    const char *table_chars;
    Py_ssize_t i, c, changed = 0;
    PyObject *input_obj = (PyObject*)self;
    const char *output_start, *del_table_chars=NULL;
    Py_ssize_t inlen, tablen, dellen = 0;
    int trans_table[256];

    if (PyBytes_Check(table)) {
        table_chars = PyBytes_AS_STRING(table);
        tablen = PyBytes_GET_SIZE(table);
    }
    else if (table == Py_None) {
        table_chars = NULL;
        tablen = 256;
    }
    else {
        if (PyObject_GetBuffer(table, &table_view, PyBUF_SIMPLE) != 0)
            return NULL;
        table_chars = table_view.buf;
        tablen = table_view.len;
    }

    if (tablen != 256) {
        PyErr_SetString(PyExc_ValueError,
          "translation table must be 256 characters long");
        PyBuffer_Release(&table_view);
        return NULL;
    }

    if (deletechars != NULL) {
        if (PyBytes_Check(deletechars)) {
            del_table_chars = PyBytes_AS_STRING(deletechars);
            dellen = PyBytes_GET_SIZE(deletechars);
        }
        else {
            if (PyObject_GetBuffer(deletechars, &del_table_view, PyBUF_SIMPLE) != 0) {
                PyBuffer_Release(&table_view);
                return NULL;
            }
            del_table_chars = del_table_view.buf;
            dellen = del_table_view.len;
        }
    }
    else {
        del_table_chars = NULL;
        dellen = 0;
    }

    inlen = PyBytes_GET_SIZE(input_obj);
    PyBytesWriter *writer = PyBytesWriter_Create(inlen);
    if (writer == NULL) {
        PyBuffer_Release(&del_table_view);
        PyBuffer_Release(&table_view);
        return NULL;
    }
    output_start = output = PyBytesWriter_GetData(writer);
    input = PyBytes_AS_STRING(input_obj);

    if (dellen == 0 && table_chars != NULL) {
        /* If no deletions are required, use faster code */
        for (i = inlen; --i >= 0; ) {
            c = Py_CHARMASK(*input++);
            *output++ = table_chars[c];
        }

        /* Check if anything changed (for returning original object) */
        /* We save this check until the end so that the compiler will */
        /* unroll the loop above leading to MUCH faster code. */
        PyObject *result;
        if (PyBytes_CheckExact(input_obj)
            && memcmp(PyBytes_AS_STRING(input_obj), output_start, inlen) == 0)
        {
            PyBytesWriter_Discard(writer);
            result = Py_NewRef(input_obj);
        }
        else {
            result = PyBytesWriter_Finish(writer);
        }

        PyBuffer_Release(&del_table_view);
        PyBuffer_Release(&table_view);
        return result;
    }

    if (table_chars == NULL) {
        for (i = 0; i < 256; i++)
            trans_table[i] = Py_CHARMASK(i);
    } else {
        for (i = 0; i < 256; i++)
            trans_table[i] = Py_CHARMASK(table_chars[i]);
    }
    PyBuffer_Release(&table_view);

    for (i = 0; i < dellen; i++)
        trans_table[(int) Py_CHARMASK(del_table_chars[i])] = -1;
    PyBuffer_Release(&del_table_view);

    for (i = inlen; --i >= 0; ) {
        c = Py_CHARMASK(*input++);
        if (trans_table[c] != -1)
            if (Py_CHARMASK(*output++ = (char)trans_table[c]) == c)
                continue;
        changed = 1;
    }
    if (!changed && PyBytes_CheckExact(input_obj)) {
        PyBytesWriter_Discard(writer);
        return Py_NewRef(input_obj);
    }
    /* Fix the size of the resulting byte string */
    return PyBytesWriter_FinishWithPointer(writer, output);
}


/*[clinic input]

@permit_long_summary
@staticmethod
bytes.maketrans

    frm: Py_buffer
    to: Py_buffer
    /

Return a translation table usable for the bytes or bytearray translate method.

The returned table will be one where each byte in frm is mapped to
the byte at the same position in to.

The bytes objects frm and to must be of the same length.
[clinic start generated code]*/

static PyObject *
bytes_maketrans_impl(Py_buffer *frm, Py_buffer *to)
/*[clinic end generated code: output=a36f6399d4b77f6f input=3a577e5badfea8f7]*/
{
    return _Py_bytes_maketrans(frm, to);
}


/*[clinic input]
bytes.replace

    old: Py_buffer
    new: Py_buffer
    /
    count: Py_ssize_t = -1
        Maximum number of occurrences to replace.
        -1 (the default value) means replace all occurrences.

Return a copy with all occurrences of substring old replaced by new.

If count is given, only the first count occurrences are replaced.
If count is not specified or -1, then all occurrences are replaced.
[clinic start generated code]*/

static PyObject *
bytes_replace_impl(PyBytesObject *self, Py_buffer *old, Py_buffer *new,
                   Py_ssize_t count)
/*[clinic end generated code: output=994fa588b6b9c104 input=cdf3cf8639297745]*/
{
    return stringlib_replace((PyObject *)self,
                             (const char *)old->buf, old->len,
                             (const char *)new->buf, new->len, count);
}

/** End DALKE **/

/*[clinic input]
@permit_long_summary
bytes.removeprefix as bytes_removeprefix

    prefix: Py_buffer
    /

Return a bytes object with the given prefix string removed if present.

If the bytes starts with the prefix string, return
bytes[len(prefix):].  Otherwise, return a copy of the original
bytes.
[clinic start generated code]*/

static PyObject *
bytes_removeprefix_impl(PyBytesObject *self, Py_buffer *prefix)
/*[clinic end generated code: output=f006865331a06ab6 input=3a2672bcee61d7a7]*/
{
    const char *self_start = PyBytes_AS_STRING(self);
    Py_ssize_t self_len = PyBytes_GET_SIZE(self);
    const char *prefix_start = prefix->buf;
    Py_ssize_t prefix_len = prefix->len;

    if (self_len >= prefix_len
        && prefix_len > 0
        && memcmp(self_start, prefix_start, prefix_len) == 0)
    {
        return _PyBytes_FromStringAndSize(self_start + prefix_len,
                                          self_len - prefix_len);
    }

    if (PyBytes_CheckExact(self)) {
        return Py_NewRef(self);
    }

    return _PyBytes_FromStringAndSize(self_start, self_len);
}

/*[clinic input]
@permit_long_summary
bytes.removesuffix as bytes_removesuffix

    suffix: Py_buffer
    /

Return a bytes object with the given suffix string removed if present.

If the bytes ends with the suffix string and that suffix is not
empty, return bytes[:-len(prefix)].  Otherwise, return a copy of the
original bytes.
[clinic start generated code]*/

static PyObject *
bytes_removesuffix_impl(PyBytesObject *self, Py_buffer *suffix)
/*[clinic end generated code: output=d887d308e3242eeb input=04df5f18a36f69d7]*/
{
    const char *self_start = PyBytes_AS_STRING(self);
    Py_ssize_t self_len = PyBytes_GET_SIZE(self);
    const char *suffix_start = suffix->buf;
    Py_ssize_t suffix_len = suffix->len;

    if (self_len >= suffix_len
        && suffix_len > 0
        && memcmp(self_start + self_len - suffix_len,
                  suffix_start, suffix_len) == 0)
    {
        return _PyBytes_FromStringAndSize(self_start,
                                          self_len - suffix_len);
    }

    if (PyBytes_CheckExact(self)) {
        return Py_NewRef(self);
    }

    return _PyBytes_FromStringAndSize(self_start, self_len);
}

/*[clinic input]
@permit_long_summary
@text_signature "($self, prefix[, start[, end]], /)"
bytes.startswith

    prefix as subobj: object
        A bytes or a tuple of bytes to try.
    start: slice_index(accept={int, NoneType}, c_default='0') = None
        Optional start position. Default: start of the bytes.
    end: slice_index(accept={int, NoneType}, c_default='PY_SSIZE_T_MAX') = None
        Optional stop position. Default: end of the bytes.
    /

Return True if the bytes starts with the specified prefix, False otherwise.
[clinic start generated code]*/

static PyObject *
bytes_startswith_impl(PyBytesObject *self, PyObject *subobj,
                      Py_ssize_t start, Py_ssize_t end)
/*[clinic end generated code: output=b1e8da1cbd528e8c input=a14efd070f15be80]*/
{
    return _Py_bytes_startswith(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                                subobj, start, end);
}

/*[clinic input]
@permit_long_summary
@text_signature "($self, suffix[, start[, end]], /)"
bytes.endswith

    suffix as subobj: object
        A bytes or a tuple of bytes to try.
    start: slice_index(accept={int, NoneType}, c_default='0') = None
         Optional start position. Default: start of the bytes.
    end: slice_index(accept={int, NoneType}, c_default='PY_SSIZE_T_MAX') = None
         Optional stop position. Default: end of the bytes.
    /

Return True if the bytes ends with the specified suffix, False otherwise.
[clinic start generated code]*/

static PyObject *
bytes_endswith_impl(PyBytesObject *self, PyObject *subobj, Py_ssize_t start,
                    Py_ssize_t end)
/*[clinic end generated code: output=038b633111f3629d input=49e383eaaf292713]*/
{
    return _Py_bytes_endswith(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                              subobj, start, end);
}


/*[clinic input]
bytes.decode

    encoding: str(c_default="NULL") = 'utf-8'
        The encoding with which to decode the bytes.
    errors: str(c_default="NULL") = 'strict'
        The error handling scheme to use for the handling of decoding
        errors.  The default is 'strict' meaning that decoding errors
        raise a UnicodeDecodeError.  Other possible values are 'ignore'
        and 'replace' as well as any other name registered with
        codecs.register_error that can handle UnicodeDecodeErrors.

Decode the bytes using the codec registered for encoding.
[clinic start generated code]*/

static PyObject *
bytes_decode_impl(PyBytesObject *self, const char *encoding,
                  const char *errors)
/*[clinic end generated code: output=5649a53dde27b314 input=94e9b8524f1d7f37]*/
{
    return PyUnicode_FromEncodedObject((PyObject*)self, encoding, errors);
}


/*[clinic input]
@permit_long_summary
bytes.splitlines

    keepends: bool = False

Return a list of the lines in the bytes, breaking at line boundaries.

Line breaks are not included in the resulting list unless keepends
is given and true.
[clinic start generated code]*/

static PyObject *
bytes_splitlines_impl(PyBytesObject *self, int keepends)
/*[clinic end generated code: output=3484149a5d880ffb input=8734672f34430514]*/
{
    return stringlib_splitlines(
        (PyObject*) self, PyBytes_AS_STRING(self),
        PyBytes_GET_SIZE(self), keepends
        );
}

/*[clinic input]
@classmethod
bytes.fromhex

    string: object
    /

Create a bytes object from a string of hexadecimal numbers.

Spaces between two numbers are accepted.
Example: bytes.fromhex('B9 01EF') -> b'\\xb9\\x01\\xef'.
[clinic start generated code]*/

static PyObject *
bytes_fromhex_impl(PyTypeObject *type, PyObject *string)
/*[clinic end generated code: output=0973acc63661bb2e input=f37d98ed51088a21]*/
{
    PyObject *result = _PyBytes_FromHex(string, 0);
    if (type != &PyBytes_Type && result != NULL) {
        Py_SETREF(result, PyObject_CallOneArg((PyObject *)type, result));
    }
    return result;
}

PyObject*
_PyBytes_FromHex(PyObject *string, int use_bytearray)
{
    Py_ssize_t hexlen, invalid_char;
    unsigned int top, bot;
    const Py_UCS1 *str, *start, *end;
    PyBytesWriter *writer = NULL;
    Py_buffer view;
    view.obj = NULL;

    if (PyUnicode_Check(string)) {
        hexlen = PyUnicode_GET_LENGTH(string);

        if (!PyUnicode_IS_ASCII(string)) {
            const void *data = PyUnicode_DATA(string);
            int kind = PyUnicode_KIND(string);
            Py_ssize_t i;

            /* search for the first non-ASCII character */
            for (i = 0; i < hexlen; i++) {
                if (PyUnicode_READ(kind, data, i) >= 128)
                    break;
            }
            invalid_char = i;
            goto error;
        }

        assert(PyUnicode_KIND(string) == PyUnicode_1BYTE_KIND);
        str = PyUnicode_1BYTE_DATA(string);
    }
    else if (PyObject_CheckBuffer(string)) {
        if (PyObject_GetBuffer(string, &view, PyBUF_SIMPLE) != 0) {
            return NULL;
        }
        hexlen = view.len;
        str = view.buf;
    }
    else {
        PyErr_Format(PyExc_TypeError,
                     "fromhex() argument must be str or bytes-like, not %T",
                     string);
        return NULL;
    }

    /* This overestimates if there are spaces */
    if (use_bytearray) {
        writer = _PyBytesWriter_CreateByteArray(hexlen / 2);
    }
    else {
        writer = PyBytesWriter_Create(hexlen / 2);
    }
    if (writer == NULL) {
        goto release_buffer;
    }
    char *buf = PyBytesWriter_GetData(writer);

    start = str;
    end = str + hexlen;
    while (str < end) {
        /* skip over spaces in the input */
        if (Py_ISSPACE(*str)) {
            do {
                str++;
                if (str >= end) {
                    goto done;
                }
            } while (Py_ISSPACE(*str));
        }

        top = _PyLong_DigitValue[*str];
        if (top >= 16) {
            invalid_char = str - start;
            goto error;
        }

        str++;
        if (str >= end) {
            invalid_char = -1;
            goto error;
        }

        bot = _PyLong_DigitValue[*str];
        if (bot >= 16) {
            invalid_char = str - start;
            goto error;
        }
        str++;

        *buf++ = (unsigned char)((top << 4) + bot);
    }

  done:
    if (view.obj != NULL) {
       PyBuffer_Release(&view);
    }
    return PyBytesWriter_FinishWithPointer(writer, buf);

  error:
    if (invalid_char == -1) {
        PyErr_SetString(PyExc_ValueError,
                        "fromhex() arg must contain an even number of hexadecimal digits");
    } else {
        PyErr_Format(PyExc_ValueError,
                     "non-hexadecimal number found in "
                     "fromhex() arg at position %zd", invalid_char);
    }
    PyBytesWriter_Discard(writer);

  release_buffer:
    if (view.obj != NULL) {
        PyBuffer_Release(&view);
    }
    return NULL;
}

/*[clinic input]
bytes.hex

    sep: object = NULL
        An optional single character or byte to separate hex bytes.
    bytes_per_sep: Py_ssize_t = 1
        How many bytes between separators.  Positive values count from
        the right, negative values count from the left.

Create a string of hexadecimal numbers from a bytes object.

Example:
>>> value = b'\xb9\x01\xef'
>>> value.hex()
'b901ef'
>>> value.hex(':')
'b9:01:ef'
>>> value.hex(':', 2)
'b9:01ef'
>>> value.hex(':', -2)
'b901:ef'
[clinic start generated code]*/

static PyObject *
bytes_hex_impl(PyBytesObject *self, PyObject *sep, Py_ssize_t bytes_per_sep)
/*[clinic end generated code: output=588821f02cb9d8f5 input=b8d40cf203d172dc]*/
{
    const char *argbuf = PyBytes_AS_STRING(self);
    Py_ssize_t arglen = PyBytes_GET_SIZE(self);
    return _Py_strhex_with_sep(argbuf, arglen, sep, bytes_per_sep);
}

static PyObject *
bytes_getnewargs(PyObject *op, PyObject *Py_UNUSED(dummy))
{
    PyBytesObject *v = _PyBytes_CAST(op);
    return Py_BuildValue("(y#)", v->ob_sval, Py_SIZE(v));
}


static PyMethodDef
bytes_methods[] = {
    {"__getnewargs__", bytes_getnewargs,  METH_NOARGS},
    BYTES___BYTES___METHODDEF
    {"capitalize", stringlib_capitalize, METH_NOARGS,
     _Py_capitalize__doc__},
    STRINGLIB_CENTER_METHODDEF
    BYTES_COUNT_METHODDEF
    BYTES_DECODE_METHODDEF
    BYTES_ENDSWITH_METHODDEF
    STRINGLIB_EXPANDTABS_METHODDEF
    BYTES_FIND_METHODDEF
    BYTES_FROMHEX_METHODDEF
    BYTES_HEX_METHODDEF
    BYTES_INDEX_METHODDEF
    {"isalnum", stringlib_isalnum, METH_NOARGS,
     _Py_isalnum__doc__},
    {"isalpha", stringlib_isalpha, METH_NOARGS,
     _Py_isalpha__doc__},
    {"isascii", stringlib_isascii, METH_NOARGS,
     _Py_isascii__doc__},
    {"isdigit", stringlib_isdigit, METH_NOARGS,
     _Py_isdigit__doc__},
    {"islower", stringlib_islower, METH_NOARGS,
     _Py_islower__doc__},
    {"isspace", stringlib_isspace, METH_NOARGS,
     _Py_isspace__doc__},
    {"istitle", stringlib_istitle, METH_NOARGS,
     _Py_istitle__doc__},
    {"isupper", stringlib_isupper, METH_NOARGS,
     _Py_isupper__doc__},
    BYTES_JOIN_METHODDEF
    STRINGLIB_LJUST_METHODDEF
    {"lower", stringlib_lower, METH_NOARGS, _Py_lower__doc__},
    BYTES_LSTRIP_METHODDEF
    BYTES_MAKETRANS_METHODDEF
    BYTES_PARTITION_METHODDEF
    BYTES_REPLACE_METHODDEF
    BYTES_REMOVEPREFIX_METHODDEF
    BYTES_REMOVESUFFIX_METHODDEF
    BYTES_RFIND_METHODDEF
    BYTES_RINDEX_METHODDEF
    STRINGLIB_RJUST_METHODDEF
    BYTES_RPARTITION_METHODDEF
    BYTES_RSPLIT_METHODDEF
    BYTES_RSTRIP_METHODDEF
    BYTES_SPLIT_METHODDEF
    BYTES_SPLITLINES_METHODDEF
    BYTES_STARTSWITH_METHODDEF
    BYTES_STRIP_METHODDEF
    {"swapcase", stringlib_swapcase, METH_NOARGS,
     _Py_swapcase__doc__},
    {"title", stringlib_title, METH_NOARGS, _Py_title__doc__},
    BYTES_TRANSLATE_METHODDEF
    {"upper", stringlib_upper, METH_NOARGS, _Py_upper__doc__},
    STRINGLIB_ZFILL_METHODDEF
    {NULL,     NULL}                         /* sentinel */
};

static PyObject *
bytes_mod(PyObject *self, PyObject *arg)
{
    if (!PyBytes_Check(self)) {
        Py_RETURN_NOTIMPLEMENTED;
    }
    return _PyBytes_FormatEx(PyBytes_AS_STRING(self), PyBytes_GET_SIZE(self),
                             arg, 0);
}

static PyNumberMethods bytes_as_number = {
    0,              /*nb_add*/
    0,              /*nb_subtract*/
    0,              /*nb_multiply*/
    bytes_mod,      /*nb_remainder*/
};

static PyObject *
bytes_subtype_new(PyTypeObject *, PyObject *);

/*[clinic input]
@vectorcall
@classmethod
bytes.__new__ as bytes_new

    source as x: object = NULL
    encoding: str = NULL
    errors: str = NULL

[clinic start generated code]*/

static PyObject *
bytes_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
               const char *errors)
/*[clinic end generated code: output=1e0c471be311a425 input=b0248d22e221a095]*/
{
    PyObject *bytes;
    PyObject *func;
    Py_ssize_t size;

    if (x == NULL) {
        if (encoding != NULL || errors != NULL) {
            PyErr_SetString(PyExc_TypeError,
                            encoding != NULL ?
                            "encoding without a string argument" :
                            "errors without a string argument");
            return NULL;
        }
        bytes = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
    }
    else if (encoding != NULL) {
        /* Encode via the codec registry */
        if (!PyUnicode_Check(x)) {
            PyErr_SetString(PyExc_TypeError,
                            "encoding without a string argument");
            return NULL;
        }
        bytes = PyUnicode_AsEncodedString(x, encoding, errors);
    }
    else if (errors != NULL) {
        PyErr_SetString(PyExc_TypeError,
                        PyUnicode_Check(x) ?
                        "string argument without an encoding" :
                        "errors without a string argument");
        return NULL;
    }
    /* We'd like to call PyObject_Bytes here, but we need to check for an
       integer argument before deferring to PyBytes_FromObject, something
       PyObject_Bytes doesn't do. */
    else if ((func = _PyObject_LookupSpecial(x, &_Py_ID(__bytes__))) != NULL) {
        bytes = _PyObject_CallNoArgs(func);
        Py_DECREF(func);
        if (bytes == NULL)
            return NULL;
        if (!PyBytes_Check(bytes)) {
            PyErr_Format(PyExc_TypeError,
                         "%T.__bytes__() must return a bytes, not %T",
                         x, bytes);
            Py_DECREF(bytes);
            return NULL;
        }
    }
    else if (PyErr_Occurred())
        return NULL;
    else if (PyUnicode_Check(x)) {
        PyErr_SetString(PyExc_TypeError,
                        "string argument without an encoding");
        return NULL;
    }
    /* Is it an integer? */
    else if (_PyIndex_Check(x)) {
        size = PyNumber_AsSsize_t(x, PyExc_OverflowError);
        if (size == -1 && PyErr_Occurred()) {
            if (!PyErr_ExceptionMatches(PyExc_TypeError))
                return NULL;
            PyErr_Clear();  /* fall through */
            bytes = PyBytes_FromObject(x);
        }
        else {
            if (size < 0) {
                PyErr_SetString(PyExc_ValueError, "negative count");
                return NULL;
            }
            bytes = _PyBytes_FromSizeZero(size);
        }
    }
    else {
        bytes = PyBytes_FromObject(x);
    }

    if (bytes != NULL && type != &PyBytes_Type) {
        Py_SETREF(bytes, bytes_subtype_new(type, bytes));
    }

    return bytes;
}

static PyObject*
_PyBytes_FromBuffer(PyObject *x)
{
    Py_buffer view;
    if (PyObject_GetBuffer(x, &view, PyBUF_FULL_RO) < 0)
        return NULL;

    PyBytesWriter *writer = PyBytesWriter_Create(view.len);
    if (writer == NULL) {
        goto fail;
    }

    if (PyBuffer_ToContiguous(PyBytesWriter_GetData(writer),
                              &view, view.len, 'C') < 0) {
        goto fail;
    }

    PyBuffer_Release(&view);
    return PyBytesWriter_Finish(writer);

fail:
    PyBytesWriter_Discard(writer);
    PyBuffer_Release(&view);
    return NULL;
}

/* Fast path for a list or tuple of ints.
   Return 1 on success (*result set to the new bytes object),
   0 to fall back to the slow path, or -1 on error (with an exception set). */
static int
_PyBytes_FromSequence_lock_held(PyObject *x, PyObject **result)
{
    *result = NULL;
    Py_ssize_t size = PySequence_Fast_GET_SIZE(x);
    PyBytesWriter *writer = PyBytesWriter_Create(size);
    if (writer == NULL) {
        return -1;
    }
    char *str = PyBytesWriter_GetData(writer);

    PyObject *const *items = PySequence_Fast_ITEMS(x);
    for (Py_ssize_t i = 0; i < size; i++) {
        Py_ssize_t value = PyLong_AsSsize_t(items[i]);
        if (value == -1 && PyErr_Occurred()) {
            PyBytesWriter_Discard(writer);
            PyErr_Clear();
            return 0;
        }

        if (value < 0 || value >= 256) {
            PyErr_SetString(PyExc_ValueError,
                            "bytes must be in range(0, 256)");
            PyBytesWriter_Discard(writer);
            return -1;
        }
        *str++ = (char) value;
    }
    *result = PyBytesWriter_Finish(writer);
    return *result != NULL ? 1 : -1;
}

static PyObject *
_PyBytes_FromIterator(PyObject *it, PyObject *x)
{
    Py_ssize_t i, size;

    /* For iterator version, create a bytes object and resize as needed */
    size = PyObject_LengthHint(x, 64);
    if (size == -1 && PyErr_Occurred())
        return NULL;

    PyBytesWriter *writer = PyBytesWriter_Create(size);
    if (writer == NULL) {
        return NULL;
    }
    size = _PyBytesWriter_ResizeToAllocated(writer);
    char *str = PyBytesWriter_GetData(writer);

    /* Run the iterator to exhaustion */
    for (i = 0; ; i++) {
        PyObject *item;
        Py_ssize_t value;

        /* Get the next item */
        item = PyIter_Next(it);
        if (item == NULL) {
            if (PyErr_Occurred())
                goto error;
            break;
        }

        /* Interpret it as an int (__index__) */
        value = PyNumber_AsSsize_t(item, NULL);
        Py_DECREF(item);
        if (value == -1 && PyErr_Occurred())
            goto error;

        /* Range check */
        if (value < 0 || value >= 256) {
            PyErr_SetString(PyExc_ValueError,
                            "bytes must be in range(0, 256)");
            goto error;
        }

        /* Append the byte */
        if (i >= size) {
            str = _PyBytesWriter_ResizeAndUpdatePointer(writer, size + 1, str);
            if (str == NULL) {
                goto error;
            }

            // Set the writer size to its allocated size
            size = _PyBytesWriter_ResizeToAllocated(writer);
        }
        *str++ = (char) value;
    }
    return PyBytesWriter_FinishWithPointer(writer, str);

  error:
    PyBytesWriter_Discard(writer);
    return NULL;
}

PyObject *
PyBytes_FromObject(PyObject *x)
{
    PyObject *it, *result;

    if (x == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }

    if (PyBytes_CheckExact(x)) {
        return Py_NewRef(x);
    }

    /* Use the modern buffer interface */
    if (PyObject_CheckBuffer(x))
        return _PyBytes_FromBuffer(x);

    if (PyList_CheckExact(x) || PyTuple_CheckExact(x)) {
        int rc;
        Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST(x);
        rc = _PyBytes_FromSequence_lock_held(x, &result);
        Py_END_CRITICAL_SECTION_SEQUENCE_FAST();
        if (rc != 0) {
            return result;
        }
    }

    if (!PyUnicode_Check(x)) {
        it = PyObject_GetIter(x);
        if (it != NULL) {
            result = _PyBytes_FromIterator(it, x);
            Py_DECREF(it);
            return result;
        }
        if (!PyErr_ExceptionMatches(PyExc_TypeError)) {
            return NULL;
        }
    }

    PyErr_Format(PyExc_TypeError,
                 "cannot convert '%.200s' object to bytes",
                 Py_TYPE(x)->tp_name);
    return NULL;
}

/* This allocator is needed for subclasses don't want to use __new__.
 * See https://github.com/python/cpython/issues/91020#issuecomment-1096793239
 *
 * This allocator will be removed when ob_shash is removed.
 */
static PyObject *
bytes_type_alloc(PyTypeObject *self, Py_ssize_t nitems)
{
    // Initialize memory to zero
    PyBytesObject *obj = (PyBytesObject*)PyType_GenericAlloc(self, nitems);
    if (obj == NULL) {
        return NULL;
    }
    set_ob_shash_unsafe(obj, -1);
    return (PyObject*)obj;
}

static PyObject *
bytes_subtype_new(PyTypeObject *type, PyObject *tmp)
{
    PyObject *pnew;
    Py_ssize_t n;

    assert(PyType_IsSubtype(type, &PyBytes_Type));
    assert(PyBytes_Check(tmp));
    n = PyBytes_GET_SIZE(tmp);
    pnew = type->tp_alloc(type, n);
    if (pnew != NULL) {
        memcpy(PyBytes_AS_STRING(pnew), PyBytes_AS_STRING(tmp), n+1);
        set_ob_shash_unsafe((PyBytesObject*)pnew,
                            get_ob_shash((PyBytesObject *)tmp));
    }
    return pnew;
}

PyDoc_STRVAR(bytes_doc,
"bytes(iterable_of_ints) -> bytes\n\
bytes(string, encoding[, errors]) -> bytes\n\
bytes(bytes_or_buffer) -> immutable copy of bytes_or_buffer\n\
bytes(int) -> bytes object of size given by the parameter initialized with null bytes\n\
bytes() -> empty bytes object\n\
\n\
Construct an immutable array of bytes from:\n\
  - an iterable yielding integers in range(256)\n\
  - a text string encoded using the specified encoding\n\
  - any object implementing the buffer API.\n\
  - an integer");

static PyObject *bytes_iter(PyObject *seq);


static _PyObjectIndexPair
bytes_iteritem(PyObject *obj, Py_ssize_t index)
{
    PyBytesObject *a = _PyBytes_CAST(obj);
    if (index >= Py_SIZE(a)) {
        return (_PyObjectIndexPair) { .object = NULL, .index = index };
    }
    PyObject *l = _PyLong_FromUnsignedChar((unsigned char)a->ob_sval[index]);
    return (_PyObjectIndexPair) { .object = l, .index = index + 1 };
}

#ifdef Py_DEBUG
void
_PyBytes_CheckOverflow(PyObject *self, void *addr, const char *type_name)
{
    // Make sure that the trailing null byte was not modified
    char *data = PyBytes_AS_STRING(self);
    Py_ssize_t size = PyBytes_GET_SIZE(self);
    if (data[size] != '\0') {
        _Py_FatalErrorFormat(__func__,
                             "Buffer overflow detected in %s object %p "
                             "at position %zd",
                             type_name, addr, size);
    }
}


static void
bytes_dealloc(PyObject *op)
{
    PyBytesObject *self = _PyBytes_CAST(op);
    _PyBytes_CheckOverflow(op, op, "bytes");
    Py_TYPE(self)->tp_free((PyObject *)self);
}
#endif


PyTypeObject PyBytes_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "bytes",
    PyBytesObject_SIZE,
    sizeof(char),
#ifdef Py_DEBUG
    bytes_dealloc,                              /* tp_dealloc */
#else
    0,                                          /* tp_dealloc */
#endif
    0,                                          /* tp_vectorcall_offset */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_as_async */
    bytes_repr,                                 /* tp_repr */
    &bytes_as_number,                           /* tp_as_number */
    &bytes_as_sequence,                         /* tp_as_sequence */
    &bytes_as_mapping,                          /* tp_as_mapping */
    bytes_hash,                                 /* tp_hash */
    0,                                          /* tp_call */
    bytes_str,                                  /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    &bytes_as_buffer,                           /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
        Py_TPFLAGS_BYTES_SUBCLASS |
        _Py_TPFLAGS_MATCH_SELF,               /* tp_flags */
    bytes_doc,                                  /* tp_doc */
    0,                                          /* tp_traverse */
    0,                                          /* tp_clear */
    bytes_richcompare,                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    bytes_iter,                                 /* tp_iter */
    0,                                          /* tp_iternext */
    bytes_methods,                              /* tp_methods */
    0,                                          /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    0,                                          /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    0,                                          /* tp_init */
    bytes_type_alloc,                           /* tp_alloc */
    bytes_new,                                  /* tp_new */
    PyObject_Free,                              /* tp_free */
    .tp_vectorcall = bytes_vectorcall,
    .tp_version_tag = _Py_TYPE_VERSION_BYTES,
    ._tp_iteritem = bytes_iteritem,
};

void
PyBytes_Concat(PyObject **pv, PyObject *w)
{
    assert(pv != NULL);
    if (*pv == NULL)
        return;
    if (w == NULL) {
        Py_CLEAR(*pv);
        return;
    }

    if (_PyObject_IsUniquelyReferenced(*pv) && PyBytes_CheckExact(*pv)) {
        /* Only one reference, so we can resize in place */
        Py_ssize_t oldsize;
        Py_buffer wb;

        if (PyObject_GetBuffer(w, &wb, PyBUF_SIMPLE) != 0) {
            PyErr_Format(PyExc_TypeError, "can't concat %.100s to %.100s",
                         Py_TYPE(w)->tp_name, Py_TYPE(*pv)->tp_name);
            Py_CLEAR(*pv);
            return;
        }

        oldsize = PyBytes_GET_SIZE(*pv);
        if (oldsize > PY_SSIZE_T_MAX - wb.len) {
            PyErr_NoMemory();
            goto error;
        }
        if (_PyBytes_Resize(pv, oldsize + wb.len) < 0)
            goto error;

        memcpy(PyBytes_AS_STRING(*pv) + oldsize, wb.buf, wb.len);
        PyBuffer_Release(&wb);
        return;

      error:
        PyBuffer_Release(&wb);
        Py_CLEAR(*pv);
        return;
    }

    else {
        /* Multiple references, need to create new object */
        PyObject *v;
        v = _PyBytes_Concat(*pv, w);
        Py_SETREF(*pv, v);
    }
}

void
PyBytes_ConcatAndDel(PyObject **pv, PyObject *w)
{
    PyBytes_Concat(pv, w);
    Py_XDECREF(w);
}


#ifndef NDEBUG
// Make sure that a bytes object can still be mutated.
//
// Usage: assert(_PyBytes_IsMutable(obj)).
int
_PyBytes_IsMutable(PyObject *self)
{
    assert(PyBytes_Check(self));
    // Do not use _PyObject_IsUniquelyReferenced(): this function is called
    // by bytearray and PyBytesWriter which can be used by multiple threads.
    assert(Py_REFCNT(self) == 1);
    assert(!_Py_IsImmortal(self));

    // Check that the object is not a singleton
    Py_ssize_t size = PyBytes_GET_SIZE(self);
    if (size == 0) {
        assert(self != bytes_get_empty());
    }
    else if (size == 1) {
        unsigned char ch = PyBytes_AS_STRING(self)[0];
        assert(self != (PyObject*)CHARACTER(ch));
    }

    // gh-158219: The hash value must not be cached yet. Otherwise, it means
    // that the bytes object was already used in Python somehow (ex: as a
    // dictionary key).
    assert(get_ob_shash((PyBytesObject *)self) == -1);

    return 1;
}
#endif


static inline int
bytes_resize_inplace(PyObject **pv, Py_ssize_t newsize)
{
    PyObject *v = *pv;
    // Do not test _PyObject_IsUniquelyReferenced(). The function is used by
    // PyBytesWriter_FinishWithSize() and its caller can have its own lock.
    assert(Py_REFCNT(v) == 1);
    assert(PyBytes_GET_SIZE(v) >= 1);
    assert(newsize >= 1);
    assert(get_ob_shash((PyBytesObject *)v) == -1);

    // Only mutable bytes can be resized in-place
    assert(_PyBytes_IsMutable(v));

    if ((size_t)newsize > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
        PyErr_SetString(PyExc_OverflowError,
                        "byte string is too large");
        return -1;
    }

#ifdef Py_TRACE_REFS
    _Py_ForgetReference(v);
#endif
    _PyReftracerTrack(v, PyRefTracer_DESTROY);

    PyObject *result = PyObject_Realloc(v, PyBytesObject_SIZE + newsize);
    if (result == NULL) {
#ifdef Py_TRACE_REFS
        _Py_AddToAllObjects(v);
#endif
        _PyReftracerTrack(v, PyRefTracer_CREATE);

        PyErr_NoMemory();
        return -1;
    }

    *pv = result;
    v = result;
    _Py_NewReferenceNoTotal(v);
    PyBytesObject *sv = (PyBytesObject *)v;
    Py_SET_SIZE(sv, newsize);
    sv->ob_sval[newsize] = '\0';
    assert(_PyBytes_IsMutable(*pv));
    return 0;
}


/* The following function breaks the notion that bytes are immutable:
   it changes the size of a bytes object.  You can think of it
   as creating a new bytes object and destroying the old one, only
   more efficiently.
   Note that if there's not enough memory to resize the bytes object, the
   original bytes object at *pv is deallocated, *pv is set to NULL, an "out of
   memory" exception is set, and -1 is returned.  Else (on success) 0 is
   returned, and the value in *pv may or may not be the same as on input.
   As always, an extra byte is allocated for a trailing \0 byte (newsize
   does *not* include that), and a trailing \0 byte is stored.
*/

// Similar to _PyBytes_Resize(), but leaves the object unchanged on error.
int
_PyBytes_ResizeKeepOnError(PyObject **pv, Py_ssize_t newsize)
{
    PyObject *v = *pv;

    if (!PyBytes_Check(v) || newsize < 0) {
        PyErr_BadInternalCall();
        return -1;
    }

    Py_ssize_t oldsize = PyBytes_GET_SIZE(v);
    if (oldsize == newsize) {
        // Leave the object unchanged if the new size is the same as the old
        // size, even if the object is not uniquely referenced or if the hash
        // value was already computed.
        return 0;
    }

    if (oldsize == 0) {
        assert(newsize >= 1);
        PyObject *result = bytes_alloc(newsize);
        if (result == NULL) {
            return -1;
        }
        *pv = result;
        Py_DECREF(v);
        assert(_PyBytes_IsMutable(*pv));
        return 0;
    }

    if (newsize == 0) {
        *pv = bytes_get_empty();  // cannot fail
        Py_DECREF(v);
        return 0;
    }

    if (!_PyObject_IsUniquelyReferenced(v)
        // Return a copy if the hash value was already computed
        || get_ob_shash((PyBytesObject *)v) != -1)
    {
        // Allocate and then copy so we don't get a shared immortal
        // one-character singleton!
        PyObject *result = bytes_alloc(newsize);
        if (!result) {
            return -1;
        }

        memcpy(PyBytes_AS_STRING(result), PyBytes_AS_STRING(v),
               Py_MIN(oldsize, newsize));
        *pv = result;
        Py_DECREF(v);
        assert(_PyBytes_IsMutable(*pv));
        return 0;
    }

    return bytes_resize_inplace(pv, newsize);
}


int
_PyBytes_Resize(PyObject **pv, Py_ssize_t newsize)
{
    int res = _PyBytes_ResizeKeepOnError(pv, newsize);
    if (res < 0) {
        PyObject *v = *pv;
        *pv = NULL;
        Py_DECREF(v);
    }
    return res;
}


/*********************** Bytes Iterator ****************************/

typedef struct {
    PyObject_HEAD
    Py_ssize_t it_index;
    PyBytesObject *it_seq; /* Set to NULL when iterator is exhausted */
} striterobject;

#define _striterobject_CAST(op)  ((striterobject *)(op))

static void
striter_dealloc(PyObject *op)
{
    striterobject *it = _striterobject_CAST(op);
    _PyObject_GC_UNTRACK(it);
    Py_XDECREF(it->it_seq);
    PyObject_GC_Del(it);
}

static int
striter_traverse(PyObject *op, visitproc visit, void *arg)
{
    striterobject *it = _striterobject_CAST(op);
    Py_VISIT(it->it_seq);
    return 0;
}

static PyObject *
striter_next(PyObject *op)
{
    striterobject *it = _striterobject_CAST(op);
    PyBytesObject *seq;

    assert(it != NULL);
    seq = it->it_seq;
    if (seq == NULL)
        return NULL;
    assert(PyBytes_Check(seq));

    if (it->it_index < PyBytes_GET_SIZE(seq)) {
        return _PyLong_FromUnsignedChar(
            (unsigned char)seq->ob_sval[it->it_index++]);
    }

    it->it_seq = NULL;
    Py_DECREF(seq);
    return NULL;
}

static PyObject *
striter_len(PyObject *op, PyObject *Py_UNUSED(ignored))
{
    striterobject *it = _striterobject_CAST(op);
    Py_ssize_t len = 0;
    if (it->it_seq)
        len = PyBytes_GET_SIZE(it->it_seq) - it->it_index;
    return PyLong_FromSsize_t(len);
}

PyDoc_STRVAR(length_hint_doc,
             "Private method returning an estimate of len(list(it)).");

static PyObject *
striter_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))
{
    PyObject *iter = _PyEval_GetBuiltin(&_Py_ID(iter));

    /* _PyEval_GetBuiltin can invoke arbitrary code,
     * call must be before access of iterator pointers.
     * see issue #101765 */
    striterobject *it = _striterobject_CAST(op);
    if (it->it_seq != NULL) {
        return Py_BuildValue("N(O)n", iter, it->it_seq, it->it_index);
    } else {
        return Py_BuildValue("N(())", iter);
    }
}

PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");

static PyObject *
striter_setstate(PyObject *op, PyObject *state)
{
    Py_ssize_t index = PyLong_AsSsize_t(state);
    if (index == -1 && PyErr_Occurred())
        return NULL;
    striterobject *it = _striterobject_CAST(op);
    if (it->it_seq != NULL) {
        if (index < 0)
            index = 0;
        else if (index > PyBytes_GET_SIZE(it->it_seq))
            index = PyBytes_GET_SIZE(it->it_seq); /* iterator exhausted */
        it->it_index = index;
    }
    Py_RETURN_NONE;
}

PyDoc_STRVAR(setstate_doc, "Set state information for unpickling.");

static PyMethodDef striter_methods[] = {
    {"__length_hint__", striter_len, METH_NOARGS, length_hint_doc},
    {"__reduce__",      striter_reduce, METH_NOARGS, reduce_doc},
    {"__setstate__",    striter_setstate, METH_O, setstate_doc},
    {NULL,              NULL}           /* sentinel */
};

PyTypeObject PyBytesIter_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "bytes_iterator",                           /* tp_name */
    sizeof(striterobject),                      /* tp_basicsize */
    0,                                          /* tp_itemsize */
    /* methods */
    striter_dealloc,                            /* tp_dealloc */
    0,                                          /* tp_vectorcall_offset */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_as_async */
    0,                                          /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
    0,                                          /* tp_doc */
    striter_traverse,                           /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    PyObject_SelfIter,                          /* tp_iter */
    striter_next,                               /* tp_iternext */
    striter_methods,                            /* tp_methods */
    0,
};

static PyObject *
bytes_iter(PyObject *seq)
{
    striterobject *it;

    if (!PyBytes_Check(seq)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    it = PyObject_GC_New(striterobject, &PyBytesIter_Type);
    if (it == NULL)
        return NULL;
    it->it_index = 0;
    it->it_seq = (PyBytesObject *)Py_NewRef(seq);
    _PyObject_GC_TRACK(it);
    return (PyObject *)it;
}


void
_PyBytes_RepeatBuffer(char* dest, Py_ssize_t len_dest,
    const char* src, Py_ssize_t len_src)
{
    if (len_dest == 0) {
        return;
    }
    if (len_src == 1) {
        memset(dest, src[0], len_dest);
    }
    else {
        if (src != dest) {
            memcpy(dest, src, len_src);
        }
        Py_ssize_t copied = len_src;
        while (copied < len_dest) {
            Py_ssize_t bytes_to_copy = Py_MIN(copied, len_dest - copied);
            memcpy(dest + copied, dest, bytes_to_copy);
            copied += bytes_to_copy;
        }
    }
}


// --- PyBytesWriter API -----------------------------------------------------

// Byte pattern to fill newly allocated bytes
#define PyBytesWrite_NEW_BYTE 0xff

// Use a value different than NUL (0) to be able to detect overflow writing
// one extra NUL byte which is a common error.
#define PyBytesWriter_CANARY_BYTE PYMEM_DEADBYTE


static inline Py_ssize_t
byteswriter_allocated(PyBytesWriter *writer)
{
    if (writer->obj == NULL) {
        // Reserve the last byte for the canary byte
        return sizeof(writer->small_buffer) - 1;
    }
    else if (writer->use_bytearray) {
        return PyByteArray_GET_SIZE(writer->obj);
    }
    else {
        return PyBytes_GET_SIZE(writer->obj);
    }
}


#ifdef Py_DEBUG
static void
byteswriter_write_canary_byte(PyBytesWriter *writer)
{
    unsigned char *data = (unsigned char*)_PyBytesWriter_GetData(writer);
    data[writer->size] = PyBytesWriter_CANARY_BYTE;
}


static void
byteswriter_reset_trailing_byte(PyBytesWriter *writer)
{
    // PyBytesWriter writes non-zero canary byte as the last byte.
    // bytes/bytearray expects the last byte to be a null byte.
    // Reset the last byte to null for bytes/bytearray.
    Py_ssize_t allocated = byteswriter_allocated(writer);
    char *data = _PyBytesWriter_GetData(writer);
    data[allocated] = '\0';
}
#endif


#ifndef NDEBUG
static int
byteswriter_check_consistency(PyBytesWriter *writer)
{
    PyObject *obj = writer->obj;
    if (obj != NULL) {
        if (writer->use_bytearray) {
            assert(PyByteArray_CheckExact(obj));
            // Do not use _PyObject_IsUniquelyReferenced(): the caller can have
            // its own lock to prevent a writer from being used by two threads
            // at the same time.
            assert(Py_REFCNT(obj) == 1);
            PyByteArrayObject *bytearray = (PyByteArrayObject*)obj;
            obj = bytearray->ob_bytes_object;
            assert(obj != NULL);
        }

        // Code adapted from _PyBytes_IsMutable()
        assert(PyBytes_CheckExact(obj));
        assert(_PyBytes_IsMutable(obj));
        // -1 since the last small buffer byte is used as the canary byte
        assert((size_t)PyBytes_GET_SIZE(obj) > (sizeof(writer->small_buffer) - 1));
    }

#ifdef Py_DEBUG
    const unsigned char *data = (const unsigned char*)_PyBytesWriter_GetData(writer);
    unsigned char canary = data[writer->size];
    if (canary != PyBytesWriter_CANARY_BYTE) {
        _Py_FatalErrorFormat(__func__,
                             "Buffer overflow detected in PyBytesWriter %p "
                             "at position %zd",
                             writer, writer->size);
    }
#endif
    return 1;
}
#endif


#ifdef MS_WINDOWS
   /* On Windows, overallocate by 50% is the best factor */
#  define OVERALLOCATE_FACTOR 2
#else
   /* On Linux, overallocate by 25% is the best factor */
#  define OVERALLOCATE_FACTOR 4
#endif

static inline int
byteswriter_resize(PyBytesWriter *writer, Py_ssize_t new_size, int resize)
{
    assert(new_size >= 1);

    Py_ssize_t old_allocated = byteswriter_allocated(writer);
    if (new_size <= old_allocated) {
        // Do not shrink the buffer before PyBytesWriter_FinishWithSize()
        return 0;
    }

    Py_ssize_t alloc = new_size;
    if (resize && writer->overallocate) {
        if (alloc <= (PY_SSIZE_T_MAX - alloc / OVERALLOCATE_FACTOR)) {
            alloc += alloc / OVERALLOCATE_FACTOR;
        }
    }

    if (writer->obj != NULL) {
        if (writer->use_bytearray) {
            if (PyByteArray_Resize(writer->obj, alloc)) {
#ifdef Py_DEBUG
                // bytearray can override the canary byte on error
                byteswriter_write_canary_byte(writer);
#endif
                assert(byteswriter_check_consistency(writer));
                return -1;
            }
        }
        else {
            // Can raise MemoryError or OverflowError
            if (_PyBytes_ResizeKeepOnError(&writer->obj, alloc)) {
                assert(writer->obj != NULL);
                assert(byteswriter_check_consistency(writer));
                return -1;
            }
            assert(_PyBytes_IsMutable(writer->obj));
        }
        assert(writer->obj != NULL);
    }
    else {
        char *data;
        if (writer->use_bytearray) {
            writer->obj = PyByteArray_FromStringAndSize(NULL, alloc);
            if (writer->obj == NULL) {
                return -1;
            }
            data = PyByteArray_AS_STRING(writer->obj);
        }
        else {
            writer->obj = bytes_alloc(alloc);
            if (writer->obj == NULL) {
                return -1;
            }
            assert(_PyBytes_IsMutable(writer->obj));
            data = PyBytes_AS_STRING(writer->obj);
        }

        if (resize) {
            // Copy data from the small buffer
            Py_ssize_t old_size = writer->size;
            assert((size_t)old_size <= sizeof(writer->small_buffer));
            assert(old_size <= alloc);
            memcpy(data, writer->small_buffer, old_size);
        }
    }

#ifdef Py_DEBUG
    Py_ssize_t allocated = byteswriter_allocated(writer);
    if (resize) {
        Py_ssize_t old_size = writer->size;
        assert(allocated > old_size);
        memset(_PyBytesWriter_GetData(writer) + old_size, PyBytesWrite_NEW_BYTE,
               allocated - old_size);
    }
#endif

    return 0;
}


static PyBytesWriter*
byteswriter_create(Py_ssize_t size, int use_bytearray)
{
    if (size < 0) {
        PyErr_SetString(PyExc_ValueError, "size must be >= 0");
        return NULL;
    }

    PyBytesWriter *writer = _Py_FREELIST_POP_MEM(bytes_writers);
    if (writer == NULL) {
        writer = (PyBytesWriter *)PyMem_Malloc(sizeof(PyBytesWriter));
        if (writer == NULL) {
            PyErr_NoMemory();
            return NULL;
        }
    }
    writer->obj = NULL;
    writer->size = size;
    writer->use_bytearray = use_bytearray;
    writer->overallocate = !use_bytearray;

    Py_ssize_t allocated = sizeof(writer->small_buffer) - 1;
    if (size > allocated) {
        if (byteswriter_resize(writer, size, 0) < 0) {
#ifdef Py_DEBUG
            // Write the canary byte so byteswriter_check_consistency()
            // doesn't fail in PyBytesWriter_Discard()
            writer->size = 0;
            byteswriter_write_canary_byte(writer);
#endif
            PyBytesWriter_Discard(writer);
            return NULL;
        }
    }
#ifdef Py_DEBUG
    memset(_PyBytesWriter_GetData(writer), PyBytesWrite_NEW_BYTE,
           byteswriter_allocated(writer));
    byteswriter_write_canary_byte(writer);
#endif
    assert(byteswriter_check_consistency(writer));
    return writer;
}

PyBytesWriter*
PyBytesWriter_Create(Py_ssize_t size)
{
    return byteswriter_create(size, 0);
}

PyBytesWriter*
_PyBytesWriter_CreateByteArray(Py_ssize_t size)
{
    return byteswriter_create(size, 1);
}


void
PyBytesWriter_Discard(PyBytesWriter *writer)
{
    if (writer == NULL) {
        return;
    }

    assert(byteswriter_check_consistency(writer));
    if (writer->obj != NULL) {
#ifdef Py_DEBUG
        byteswriter_reset_trailing_byte(writer);
#endif
        Py_DECREF(writer->obj);
    }
    _Py_FREELIST_FREE(bytes_writers, writer, PyMem_Free);
}


static inline PyObject*
byteswriter_finish_with_size(PyBytesWriter *writer, Py_ssize_t final_size)
{
    assert(byteswriter_check_consistency(writer));

    PyObject *result;
    if (final_size == 0 && !writer->use_bytearray) {
        result = bytes_get_empty();
        if (writer->obj != NULL) {
#ifdef Py_DEBUG
            byteswriter_reset_trailing_byte(writer);
#endif
            Py_DECREF(writer->obj);
            writer->obj = NULL;
        }
    }
    else if (writer->obj != NULL) {
        // Truncate the bytes/bytearray object if needed
#ifdef Py_DEBUG
        byteswriter_reset_trailing_byte(writer);
#endif

        if (writer->use_bytearray) {
            if (final_size != PyByteArray_GET_SIZE(writer->obj)) {
                if (PyByteArray_Resize(writer->obj, final_size)) {
                    goto error;
                }
            }
        }
        else {
            if (final_size == 1) {
                unsigned char ch = PyBytes_AS_STRING(writer->obj)[0];
                Py_SETREF(writer->obj, bytes_get_char(ch));
            }
            else if (final_size != PyBytes_GET_SIZE(writer->obj)) {
                if (bytes_resize_inplace(&writer->obj, final_size)) {
                    goto error;
                }
            }
        }

        result = writer->obj;
        writer->obj = NULL;
    }
    else {
        // Create an object from the small buffer
        const char *buffer = (const char *)writer->small_buffer;
        if (writer->use_bytearray) {
            result = PyByteArray_FromStringAndSize(buffer, final_size);
        }
        else {
            if (final_size == 1) {
                result = bytes_get_char((uint8_t)buffer[0]);
            }
            else {
                result = bytes_alloc(final_size);
                if (result == NULL) {
                    goto error;
                }
                memcpy(PyBytes_AS_STRING(result), buffer, final_size);
            }
        }
    }

    assert(writer->obj == NULL);
    _Py_FREELIST_FREE(bytes_writers, writer, PyMem_Free);
    return result;

error:
    PyBytesWriter_Discard(writer);
    return NULL;
}

PyObject*
PyBytesWriter_FinishWithSize(PyBytesWriter *writer, Py_ssize_t size)
{
    if (size < 0) {
        PyErr_Format(PyExc_ValueError, "size must be positive");
        goto error;
    }
    if (size > writer->size) {
        PyErr_SetString(PyExc_ValueError, "size larger than allocated size");
        goto error;
    }
    return byteswriter_finish_with_size(writer, size);

error:
    PyBytesWriter_Discard(writer);
    return NULL;
}

PyObject*
PyBytesWriter_Finish(PyBytesWriter *writer)
{
    return byteswriter_finish_with_size(writer, writer->size);
}


PyObject*
PyBytesWriter_FinishWithPointer(PyBytesWriter *writer, void *buf)
{
    Py_ssize_t size = (char*)buf - _PyBytesWriter_GetData(writer);
    // Call PyBytesWriter_FinishWithSize() to check size
    return PyBytesWriter_FinishWithSize(writer, size);
}


void*
PyBytesWriter_GetData(PyBytesWriter *writer)
{
    assert(byteswriter_check_consistency(writer));

    return _PyBytesWriter_GetData(writer);
}


Py_ssize_t
PyBytesWriter_GetSize(PyBytesWriter *writer)
{
    assert(byteswriter_check_consistency(writer));

    return _PyBytesWriter_GetSize(writer);
}


int
PyBytesWriter_Resize(PyBytesWriter *writer, Py_ssize_t new_size)
{
    assert(byteswriter_check_consistency(writer));

    if (new_size < 0) {
        PyErr_SetString(PyExc_ValueError, "size must be >= 0");
        return -1;
    }
    if (writer->size < new_size) {
        if (byteswriter_resize(writer, new_size, 1) < 0) {
            return -1;
        }
    }
    else {
        // The buffer is already large enough. Never shrink the buffer.
    }

    writer->size = new_size;
#ifdef Py_DEBUG
    byteswriter_write_canary_byte(writer);
#endif
    assert(byteswriter_check_consistency(writer));
    return 0;
}


static void*
_PyBytesWriter_ResizeAndUpdatePointer(PyBytesWriter *writer, Py_ssize_t size,
                                      void *data)
{
    Py_ssize_t pos = (char*)data - _PyBytesWriter_GetData(writer);
    if (PyBytesWriter_Resize(writer, size) < 0) {
        return NULL;
    }
    return _PyBytesWriter_GetData(writer) + pos;
}


int
PyBytesWriter_Grow(PyBytesWriter *writer, Py_ssize_t grow)
{
    assert(byteswriter_check_consistency(writer));

    if (grow == 0) {
        // Nothing to do
        return 0;
    }

    if (grow > 0) {
        if (grow > PY_SSIZE_T_MAX - writer->size) {
            PyErr_NoMemory();
            return -1;
        }
        Py_ssize_t new_size = writer->size + grow;

        if (byteswriter_resize(writer, new_size, 1) < 0) {
            return -1;
        }
        writer->size = new_size;
    }
    else {
        if (writer->size + grow < 0) {
            PyErr_SetString(PyExc_ValueError, "invalid size");
            return -1;
        }
        // The buffer is already large enough. Never shrink the buffer.
        writer->size = writer->size + grow;
    }

#ifdef Py_DEBUG
    byteswriter_write_canary_byte(writer);
#endif
    assert(byteswriter_check_consistency(writer));
    return 0;
}


void*
PyBytesWriter_GrowAndUpdatePointer(PyBytesWriter *writer, Py_ssize_t size,
                                   void *buf)
{
    Py_ssize_t pos = (char*)buf - _PyBytesWriter_GetData(writer);
    if (PyBytesWriter_Grow(writer, size) < 0) {
        return NULL;
    }
    return _PyBytesWriter_GetData(writer) + pos;
}


int
PyBytesWriter_WriteBytes(PyBytesWriter *writer,
                         const void *bytes, Py_ssize_t size)
{
    if (size < 0) {
        size_t len = strlen(bytes);
        if (len > (size_t)PY_SSIZE_T_MAX) {
            PyErr_NoMemory();
            return -1;
        }
        size = (Py_ssize_t)len;
    }

    Py_ssize_t pos = writer->size;
    if (PyBytesWriter_Grow(writer, size) < 0) {
        return -1;
    }
    char *buf = _PyBytesWriter_GetData(writer);
    memcpy(buf + pos, bytes, size);

    assert(byteswriter_check_consistency(writer));
    return 0;
}


int
PyBytesWriter_Format(PyBytesWriter *writer, const char *format, ...)
{
    Py_ssize_t pos = writer->size;
    Py_ssize_t old_pos = pos;
    if (PyBytesWriter_Grow(writer, strlen(format)) < 0) {
        return -1;
    }

    va_list vargs;
    va_start(vargs, format);
    char *buf = bytes_fromformat(writer, pos, format, vargs);
    va_end(vargs);

    if (buf == NULL) {
        // On error, reset the writer to its previous state (undo any write)
        writer->size = old_pos;
#ifdef Py_DEBUG
        byteswriter_write_canary_byte(writer);
#endif
        return -1;
    }

    Py_ssize_t size = buf - _PyBytesWriter_GetData(writer);
    return PyBytesWriter_Resize(writer, size);
}


// Resize the writer to its allocated size.
// Return the new size.
// The function cannot fail.
static Py_ssize_t
_PyBytesWriter_ResizeToAllocated(PyBytesWriter *writer)
{
    Py_ssize_t allocated = byteswriter_allocated(writer);
    writer->size = allocated;
#ifdef Py_DEBUG
    byteswriter_write_canary_byte(writer);
#endif

    assert(byteswriter_check_consistency(writer));
    return allocated;
}