| /* Copyright (C) 2007 Eric Blake |
| * Permission to use, copy, modify, and distribute this software |
| * is freely granted, provided that this notice is preserved. |
| */ |
| |
| /* |
| FUNCTION |
| <<fmemopen>>---open a stream around a fixed-length string |
| |
| INDEX |
| fmemopen |
| |
| ANSI_SYNOPSIS |
| #include <stdio.h> |
| FILE *fmemopen(void *restrict <[buf]>, size_t <[size]>, |
| const char *restrict <[mode]>); |
| |
| DESCRIPTION |
| <<fmemopen>> creates a seekable <<FILE>> stream that wraps a |
| fixed-length buffer of <[size]> bytes starting at <[buf]>. The stream |
| is opened with <[mode]> treated as in <<fopen>>, where append mode |
| starts writing at the first NUL byte. If <[buf]> is NULL, then |
| <[size]> bytes are automatically provided as if by <<malloc>>, with |
| the initial size of 0, and <[mode]> must contain <<+>> so that data |
| can be read after it is written. |
| |
| The stream maintains a current position, which moves according to |
| bytes read or written, and which can be one past the end of the array. |
| The stream also maintains a current file size, which is never greater |
| than <[size]>. If <[mode]> starts with <<r>>, the position starts at |
| <<0>>, and file size starts at <[size]> if <[buf]> was provided. If |
| <[mode]> starts with <<w>>, the position and file size start at <<0>>, |
| and if <[buf]> was provided, the first byte is set to NUL. If |
| <[mode]> starts with <<a>>, the position and file size start at the |
| location of the first NUL byte, or else <[size]> if <[buf]> was |
| provided. |
| |
| When reading, NUL bytes have no significance, and reads cannot exceed |
| the current file size. When writing, the file size can increase up to |
| <[size]> as needed, and NUL bytes may be embedded in the stream (see |
| <<open_memstream>> for an alternative that automatically enlarges the |
| buffer). When the stream is flushed or closed after a write that |
| changed the file size, a NUL byte is written at the current position |
| if there is still room; if the stream is not also open for reading, a |
| NUL byte is additionally written at the last byte of <[buf]> when the |
| stream has exceeded <[size]>, so that a write-only <[buf]> is always |
| NUL-terminated when the stream is flushed or closed (and the initial |
| <[size]> should take this into account). It is not possible to seek |
| outside the bounds of <[size]>. A NUL byte written during a flush is |
| restored to its previous value when seeking elsewhere in the string. |
| |
| RETURNS |
| The return value is an open FILE pointer on success. On error, |
| <<NULL>> is returned, and <<errno>> will be set to EINVAL if <[size]> |
| is zero or <[mode]> is invalid, ENOMEM if <[buf]> was NULL and memory |
| could not be allocated, or EMFILE if too many streams are already |
| open. |
| |
| PORTABILITY |
| This function is being added to POSIX 200x, but is not in POSIX 2001. |
| |
| Supporting OS subroutines required: <<sbrk>>. |
| */ |
| |
| #include <stdio.h> |
| #include <errno.h> |
| #include <string.h> |
| #include <sys/lock.h> |
| #include "local.h" |
| |
| /* Describe details of an open memstream. */ |
| typedef struct fmemcookie { |
| void *storage; /* storage to free on close */ |
| char *buf; /* buffer start */ |
| size_t pos; /* current position */ |
| size_t eof; /* current file size */ |
| size_t max; /* maximum file size */ |
| char append; /* nonzero if appending */ |
| char writeonly; /* 1 if write-only */ |
| char saved; /* saved character that lived at pos before write-only NUL */ |
| } fmemcookie; |
| |
| /* Read up to non-zero N bytes into BUF from stream described by |
| COOKIE; return number of bytes read (0 on EOF). */ |
| static _READ_WRITE_RETURN_TYPE |
| _DEFUN(fmemreader, (ptr, cookie, buf, n), |
| struct _reent *ptr _AND |
| void *cookie _AND |
| char *buf _AND |
| int n) |
| { |
| fmemcookie *c = (fmemcookie *) cookie; |
| /* Can't read beyond current size, but EOF condition is not an error. */ |
| if (c->pos > c->eof) |
| return 0; |
| if (n >= c->eof - c->pos) |
| n = c->eof - c->pos; |
| memcpy (buf, c->buf + c->pos, n); |
| c->pos += n; |
| return n; |
| } |
| |
| /* Write up to non-zero N bytes of BUF into the stream described by COOKIE, |
| returning the number of bytes written or EOF on failure. */ |
| static _READ_WRITE_RETURN_TYPE |
| _DEFUN(fmemwriter, (ptr, cookie, buf, n), |
| struct _reent *ptr _AND |
| void *cookie _AND |
| const char *buf _AND |
| int n) |
| { |
| fmemcookie *c = (fmemcookie *) cookie; |
| int adjust = 0; /* true if at EOF, but still need to write NUL. */ |
| |
| /* Append always seeks to eof; otherwise, if we have previously done |
| a seek beyond eof, ensure all intermediate bytes are NUL. */ |
| if (c->append) |
| c->pos = c->eof; |
| else if (c->pos > c->eof) |
| memset (c->buf + c->eof, '\0', c->pos - c->eof); |
| /* Do not write beyond EOF; saving room for NUL on write-only stream. */ |
| if (c->pos + n > c->max - c->writeonly) |
| { |
| adjust = c->writeonly; |
| n = c->max - c->pos; |
| } |
| /* Now n is the number of bytes being modified, and adjust is 1 if |
| the last byte is NUL instead of from buf. Write a NUL if |
| write-only; or if read-write, eof changed, and there is still |
| room. When we are within the file contents, remember what we |
| overwrite so we can restore it if we seek elsewhere later. */ |
| if (c->pos + n > c->eof) |
| { |
| c->eof = c->pos + n; |
| if (c->eof - adjust < c->max) |
| c->saved = c->buf[c->eof - adjust] = '\0'; |
| } |
| else if (c->writeonly) |
| { |
| if (n) |
| { |
| c->saved = c->buf[c->pos + n - adjust]; |
| c->buf[c->pos + n - adjust] = '\0'; |
| } |
| else |
| adjust = 0; |
| } |
| c->pos += n; |
| if (n - adjust) |
| memcpy (c->buf + c->pos - n, buf, n - adjust); |
| else |
| { |
| ptr->_errno = ENOSPC; |
| return EOF; |
| } |
| return n; |
| } |
| |
| /* Seek to position POS relative to WHENCE within stream described by |
| COOKIE; return resulting position or fail with EOF. */ |
| static _fpos_t |
| _DEFUN(fmemseeker, (ptr, cookie, pos, whence), |
| struct _reent *ptr _AND |
| void *cookie _AND |
| _fpos_t pos _AND |
| int whence) |
| { |
| fmemcookie *c = (fmemcookie *) cookie; |
| #ifndef __LARGE64_FILES |
| off_t offset = (off_t) pos; |
| #else /* __LARGE64_FILES */ |
| _off64_t offset = (_off64_t) pos; |
| #endif /* __LARGE64_FILES */ |
| |
| if (whence == SEEK_CUR) |
| offset += c->pos; |
| else if (whence == SEEK_END) |
| offset += c->eof; |
| if (offset < 0) |
| { |
| ptr->_errno = EINVAL; |
| offset = -1; |
| } |
| else if (offset > c->max) |
| { |
| ptr->_errno = ENOSPC; |
| offset = -1; |
| } |
| #ifdef __LARGE64_FILES |
| else if ((_fpos_t) offset != offset) |
| { |
| ptr->_errno = EOVERFLOW; |
| offset = -1; |
| } |
| #endif /* __LARGE64_FILES */ |
| else |
| { |
| if (c->writeonly && c->pos < c->eof) |
| { |
| c->buf[c->pos] = c->saved; |
| c->saved = '\0'; |
| } |
| c->pos = offset; |
| if (c->writeonly && c->pos < c->eof) |
| { |
| c->saved = c->buf[c->pos]; |
| c->buf[c->pos] = '\0'; |
| } |
| } |
| return (_fpos_t) offset; |
| } |
| |
| /* Seek to position POS relative to WHENCE within stream described by |
| COOKIE; return resulting position or fail with EOF. */ |
| #ifdef __LARGE64_FILES |
| static _fpos64_t |
| _DEFUN(fmemseeker64, (ptr, cookie, pos, whence), |
| struct _reent *ptr _AND |
| void *cookie _AND |
| _fpos64_t pos _AND |
| int whence) |
| { |
| _off64_t offset = (_off64_t) pos; |
| fmemcookie *c = (fmemcookie *) cookie; |
| if (whence == SEEK_CUR) |
| offset += c->pos; |
| else if (whence == SEEK_END) |
| offset += c->eof; |
| if (offset < 0) |
| { |
| ptr->_errno = EINVAL; |
| offset = -1; |
| } |
| else if (offset > c->max) |
| { |
| ptr->_errno = ENOSPC; |
| offset = -1; |
| } |
| else |
| { |
| if (c->writeonly && c->pos < c->eof) |
| { |
| c->buf[c->pos] = c->saved; |
| c->saved = '\0'; |
| } |
| c->pos = offset; |
| if (c->writeonly && c->pos < c->eof) |
| { |
| c->saved = c->buf[c->pos]; |
| c->buf[c->pos] = '\0'; |
| } |
| } |
| return (_fpos64_t) offset; |
| } |
| #endif /* __LARGE64_FILES */ |
| |
| /* Reclaim resources used by stream described by COOKIE. */ |
| static int |
| _DEFUN(fmemcloser, (ptr, cookie), |
| struct _reent *ptr _AND |
| void *cookie) |
| { |
| fmemcookie *c = (fmemcookie *) cookie; |
| _free_r (ptr, c->storage); |
| return 0; |
| } |
| |
| /* Open a memstream around buffer BUF of SIZE bytes, using MODE. |
| Return the new stream, or fail with NULL. */ |
| FILE * |
| _DEFUN(_fmemopen_r, (ptr, buf, size, mode), |
| struct _reent *ptr _AND |
| void *buf _AND |
| size_t size _AND |
| const char *mode) |
| { |
| FILE *fp; |
| fmemcookie *c; |
| int flags; |
| int dummy; |
| |
| if ((flags = __sflags (ptr, mode, &dummy)) == 0) |
| return NULL; |
| if (!size || !(buf || flags & __SAPP)) |
| { |
| ptr->_errno = EINVAL; |
| return NULL; |
| } |
| if ((fp = __sfp (ptr)) == NULL) |
| return NULL; |
| if ((c = (fmemcookie *) _malloc_r (ptr, sizeof *c + (buf ? 0 : size))) |
| == NULL) |
| { |
| __sfp_lock_acquire (); |
| fp->_flags = 0; /* release */ |
| #ifndef __SINGLE_THREAD__ |
| __lock_close_recursive (fp->_lock); |
| #endif |
| __sfp_lock_release (); |
| return NULL; |
| } |
| |
| c->storage = c; |
| c->max = size; |
| /* 9 modes to worry about. */ |
| /* w/a, buf or no buf: Guarantee a NUL after any file writes. */ |
| c->writeonly = (flags & __SWR) != 0; |
| c->saved = '\0'; |
| if (!buf) |
| { |
| /* r+/w+/a+, and no buf: file starts empty. */ |
| c->buf = (char *) (c + 1); |
| *(char *) buf = '\0'; |
| c->pos = c->eof = 0; |
| c->append = (flags & __SAPP) != 0; |
| } |
| else |
| { |
| c->buf = (char *) buf; |
| switch (*mode) |
| { |
| case 'a': |
| /* a/a+ and buf: position and size at first NUL. */ |
| buf = memchr (c->buf, '\0', size); |
| c->eof = c->pos = buf ? (char *) buf - c->buf : size; |
| if (!buf && c->writeonly) |
| /* a: guarantee a NUL within size even if no writes. */ |
| c->buf[size - 1] = '\0'; |
| c->append = 1; |
| break; |
| case 'r': |
| /* r/r+ and buf: read at beginning, full size available. */ |
| c->pos = c->append = 0; |
| c->eof = size; |
| break; |
| case 'w': |
| /* w/w+ and buf: write at beginning, truncate to empty. */ |
| c->pos = c->append = c->eof = 0; |
| *c->buf = '\0'; |
| break; |
| default: |
| abort (); |
| } |
| } |
| |
| _flockfile (fp); |
| fp->_file = -1; |
| fp->_flags = flags; |
| fp->_cookie = c; |
| fp->_read = flags & (__SRD | __SRW) ? fmemreader : NULL; |
| fp->_write = flags & (__SWR | __SRW) ? fmemwriter : NULL; |
| fp->_seek = fmemseeker; |
| #ifdef __LARGE64_FILES |
| fp->_seek64 = fmemseeker64; |
| fp->_flags |= __SL64; |
| #endif |
| fp->_close = fmemcloser; |
| _funlockfile (fp); |
| return fp; |
| } |
| |
| #ifndef _REENT_ONLY |
| FILE * |
| _DEFUN(fmemopen, (buf, size, mode), |
| void *buf _AND |
| size_t size _AND |
| const char *mode) |
| { |
| return _fmemopen_r (_REENT, buf, size, mode); |
| } |
| #endif /* !_REENT_ONLY */ |