src/strings/unicode.h

// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_STRINGS_UNICODE_H_
#define V8_STRINGS_UNICODE_H_

#include <sys/types.h>

#include "src/base/bit-field.h"
#include "src/base/vector.h"
#include "src/common/globals.h"
#include "third_party/utf8-decoder/utf8-decoder.h"
/**
 * \file
 * Definitions and convenience functions for working with unicode.
 */

namespace unibrow {

using uchar = unsigned int;

/**
 * The max length of the result of converting the case of a single
 * character.
 */
const int kMaxMappingSize = 4;

#ifndef V8_INTL_SUPPORT
template <class T, int size = 256>
class Predicate {
 public:
  inline Predicate() = default;
  inline bool get(uchar c);

 private:
  friend class Test;
  bool CalculateValue(uchar c);
  class CacheEntry {
   public:
    inline CacheEntry()
        : bit_field_(CodePointField::encode(0) | ValueField::encode(0)) {}
    inline CacheEntry(uchar code_point, bool value)
        : bit_field_(
              CodePointField::encode(CodePointField::kMask & code_point) |
              ValueField::encode(value)) {
      DCHECK_IMPLIES((CodePointField::kMask & code_point) != code_point,
                     code_point == static_cast<uchar>(-1));
    }

    uchar code_point() const { return CodePointField::decode(bit_field_); }
    bool value() const { return ValueField::decode(bit_field_); }

   private:
    using CodePointField = v8::base::BitField<uchar, 0, 21>;
    using ValueField = v8::base::BitField<bool, 21, 1>;

    uint32_t bit_field_;
  };
  static const int kSize = size;
  static const int kMask = kSize - 1;
  CacheEntry entries_[kSize];
};

// A cache used in case conversion.  It caches the value for characters
// that either have no mapping or map to a single character independent
// of context.  Characters that map to more than one character or that
// map differently depending on context are always looked up.
template <class T, int size = 256>
class Mapping {
 public:
  inline Mapping() = default;
  inline int get(uchar c, uchar n, uchar* result);

 private:
  friend class Test;
  int CalculateValue(uchar c, uchar n, uchar* result);
  struct CacheEntry {
    inline CacheEntry() : code_point_(kNoChar), offset_(0) {}
    inline CacheEntry(uchar code_point, signed offset)
        : code_point_(code_point), offset_(offset) {}
    uchar code_point_;
    signed offset_;
    static const int kNoChar = (1 << 21) - 1;
  };
  static const int kSize = size;
  static const int kMask = kSize - 1;
  CacheEntry entries_[kSize];
};

class UnicodeData {
 private:
  friend class Test;
  static int GetByteCount();
  static const uchar kMaxCodePoint;
};

#endif  // !V8_INTL_SUPPORT

class Utf16 {
 public:
  static const int kNoPreviousCharacter = -1;
  static inline bool IsSurrogatePair(int lead, int trail) {
    return IsLeadSurrogate(lead) && IsTrailSurrogate(trail);
  }
  static inline bool IsLeadSurrogate(int code) {
    return (code & 0x1ffc00) == 0xd800;
  }
  static inline bool IsTrailSurrogate(int code) {
    return (code & 0x1ffc00) == 0xdc00;
  }

  static inline int CombineSurrogatePair(uchar lead, uchar trail) {
    return 0x10000 + ((lead & 0x3ff) << 10) + (trail & 0x3ff);
  }
  static const uchar kMaxNonSurrogateCharCode = 0xffff;
  // Encoding a single UTF-16 code unit will produce 1, 2 or 3 bytes
  // of UTF-8 data.  The special case where the unit is a surrogate
  // trail produces 1 byte net, because the encoding of the pair is
  // 4 bytes and the 3 bytes that were used to encode the lead surrogate
  // can be reclaimed.
  static const int kMaxExtraUtf8BytesForOneUtf16CodeUnit = 3;
  // One UTF-16 surrogate is encoded (illegally) as 3 UTF-8 bytes.
  // The illegality stems from the surrogate not being part of a pair.
  static const int kUtf8BytesToCodeASurrogate = 3;
  static inline uint16_t LeadSurrogate(uint32_t char_code) {
    return 0xd800 + (((char_code - 0x10000) >> 10) & 0x3ff);
  }
  static inline uint16_t TrailSurrogate(uint32_t char_code) {
    return 0xdc00 + (char_code & 0x3ff);
  }
  static inline bool HasUnpairedSurrogate(const uint16_t* code_units,
                                          size_t length);

  static void ReplaceUnpairedSurrogates(const uint16_t* source_code_units,
                                        uint16_t* dest_code_units,
                                        size_t length);
};

class Latin1 {
 public:
  static const uint16_t kMaxChar = 0xff;
};

enum class Utf8Variant : uint8_t {
#if V8_ENABLE_WEBASSEMBLY
  kUtf8,        // UTF-8.  Decoding an invalid byte sequence or encoding a
                // surrogate codepoint signals an error.
  kUtf8NoTrap,  // UTF-8.  Decoding an invalid byte sequence or encoding a
                // surrogate codepoint returns null.
  kWtf8,        // WTF-8: like UTF-8, but allows isolated (but not paired)
                // surrogate codepoints to be encoded and decoded.
#endif
  kLossyUtf8,  // Lossy UTF-8: Any byte sequence can be decoded without
               // error, replacing invalid UTF-8 with the replacement
               // character (U+FFFD).  Any sequence of codepoints can be
               // encoded without error, replacing surrogates with U+FFFD.
  kLastUtf8Variant = kLossyUtf8
};

class V8_EXPORT_PRIVATE Utf8 {
 public:
  using State = Utf8DfaDecoder::State;

  static inline unsigned LengthOneByte(uint8_t chr);
  static inline unsigned Length(uchar chr, int previous);
  static inline unsigned EncodeOneByte(char* out, uint8_t c);
  static inline unsigned Encode(char* out, uchar c, int previous,
                                bool replace_invalid = false);
  static uchar CalculateValue(const uint8_t* str, size_t length,
                              size_t* cursor);

  // The unicode replacement character, used to signal invalid unicode
  // sequences (e.g. an orphan surrogate) when converting to a UTF-8 encoding.
  static const uchar kBadChar = 0xFFFD;
  static const uchar kBufferEmpty = 0x0;
  static const uchar kIncomplete = 0xFFFFFFFC;  // any non-valid code point.
  static const unsigned kMaxEncodedSize = 4;
  static const unsigned kMaxOneByteChar = 0x7f;
  static const unsigned kMaxTwoByteChar = 0x7ff;
  static const unsigned kMaxThreeByteChar = 0xffff;
  static const unsigned kMaxFourByteChar = 0x1fffff;

  // A single surrogate is coded as a 3 byte UTF-8 sequence, but two together
  // that match are coded as a 4 byte UTF-8 sequence.
  static const unsigned kBytesSavedByCombiningSurrogates = 2;
  static const unsigned kSizeOfUnmatchedSurrogate = 3;
  // The maximum size a single UTF-16 code unit may take up when encoded as
  // UTF-8.
  static const unsigned kMax16BitCodeUnitSize = 3;
  // The maximum size a single UTF-16 code unit known to be in the range
  // [0,0xff] may take up when encoded as UTF-8.
  static const unsigned kMax8BitCodeUnitSize = 2;
  static inline uchar ValueOf(const uint8_t* str, size_t length,
                              size_t* cursor);

  using Utf8IncrementalBuffer = uint32_t;
  static inline uchar ValueOfIncremental(const uint8_t** cursor, State* state,
                                         Utf8IncrementalBuffer* buffer);
  static uchar ValueOfIncrementalFinish(State* state);

  // Excludes non-characters from the set of valid code points.
  static inline bool IsValidCharacter(uchar c);

  // Validate if the input has a valid utf-8 encoding. Unlike JS source code
  // this validation function will accept any unicode code point, including
  // kBadChar and BOMs.
  //
  // This method checks for:
  // - valid utf-8 endcoding (e.g. no over-long encodings),
  // - absence of surrogates,
  // - valid code point range.
  static bool ValidateEncoding(const uint8_t* str, size_t length);

  template <typename Char>
  static size_t WriteLeadingAscii(const Char* src, char* dest, size_t size);

  // Encode the given characters as Utf8 into the provided output buffer.
  struct EncodingResult {
    size_t bytes_written;
    size_t characters_processed;
  };
  template <typename Char>
  static EncodingResult Encode(v8::base::Vector<const Char> string,
                               char* buffer, size_t capacity, bool write_null,
                               bool replace_invalid_utf8);
};

template <>
size_t unibrow::Utf8::WriteLeadingAscii<uint8_t>(const uint8_t* src, char* dest,
                                                 size_t size);

template <>
size_t unibrow::Utf8::WriteLeadingAscii<uint16_t>(const uint16_t* src,
                                                  char* dest, size_t size);

#if V8_ENABLE_WEBASSEMBLY
class V8_EXPORT_PRIVATE Wtf8 {
 public:
  // Validate that the input has a valid WTF-8 encoding.
  //
  // This method checks for:
  // - valid utf-8 endcoding (e.g. no over-long encodings),
  // - absence of surrogate pairs,
  // - valid code point range.
  //
  // In terms of the WTF-8 specification (https://simonsapin.github.io/wtf-8/),
  // this function checks for a valid "generalized UTF-8" sequence, with the
  // additional constraint that surrogate pairs are not allowed.
  static bool ValidateEncoding(const uint8_t* str, size_t length);

  static void ScanForSurrogates(v8::base::Vector<const uint8_t> wtf8,
                                std::vector<size_t>* surrogate_offsets);
};
#endif  // V8_ENABLE_WEBASSEMBLY

struct Uppercase {
  static bool Is(uchar c);
};
struct Letter {
  static bool Is(uchar c);
};
#ifndef V8_INTL_SUPPORT
struct V8_EXPORT_PRIVATE ID_Start {
  static bool Is(uchar c);
};
struct V8_EXPORT_PRIVATE ID_Continue {
  static bool Is(uchar c);
};
struct V8_EXPORT_PRIVATE WhiteSpace {
  static bool Is(uchar c);
};
#endif  // !V8_INTL_SUPPORT

// LineTerminator:       'JS_Line_Terminator' in point.properties
// https://tc39.es/ecma262/#sec-line-terminators lists exactly 4 code points:
// LF (U+000A), CR (U+000D), LS(U+2028), PS(U+2029)
V8_INLINE bool IsLineTerminator(uchar c) {
  return c == 0x000A || c == 0x000D || c == 0x2028 || c == 0x2029;
}

V8_INLINE bool IsStringLiteralLineTerminator(uchar c) {
  return c == 0x000A || c == 0x000D;
}

#ifdef V8_INTL_SUPPORT
struct V8_EXPORT_PRIVATE ToLowercase {
  static const bool kIsToLower = true;
};
struct V8_EXPORT_PRIVATE ToUppercase {
  static const bool kIsToLower = false;
};
#else
struct V8_EXPORT_PRIVATE ToLowercase {
  static const int kMaxWidth = 3;
  static const bool kIsToLower = true;
  static int Convert(uchar c, uchar n, uchar* result, bool* allow_caching_ptr);
};
struct V8_EXPORT_PRIVATE ToUppercase {
  static const int kMaxWidth = 3;
  static const bool kIsToLower = false;
  static int Convert(uchar c, uchar n, uchar* result, bool* allow_caching_ptr);
};
struct V8_EXPORT_PRIVATE Ecma262Canonicalize {
  static const int kMaxWidth = 1;
  static int Convert(uchar c, uchar n, uchar* result, bool* allow_caching_ptr);
};
struct V8_EXPORT_PRIVATE Ecma262UnCanonicalize {
  static const int kMaxWidth = 4;
  static int Convert(uchar c, uchar n, uchar* result, bool* allow_caching_ptr);
};
struct V8_EXPORT_PRIVATE CanonicalizationRange {
  static const int kMaxWidth = 1;
  static int Convert(uchar c, uchar n, uchar* result, bool* allow_caching_ptr);
};
#endif  // !V8_INTL_SUPPORT

}  // namespace unibrow

namespace v8::internal {

class UnicodeConfig {
 public:
  constexpr explicit UnicodeConfig(unibrow::Utf8Variant variant)
      : UnicodeConfig(variant, SharedFlag{false}, SharedFlag{false}) {}

  constexpr UnicodeConfig(unibrow::Utf8Variant variant,
                          SharedFlag source_shared, SharedFlag dest_shared)
      : flags_(VariantField::encode(variant) |
               SourceSharedField::encode(source_shared.value()) |
               DestSharedField::encode(dest_shared.value())) {}

  constexpr UnicodeConfig(SharedFlag source_shared, SharedFlag dest_shared)
      : flags_(SourceSharedField::encode(source_shared.value()) |
               DestSharedField::encode(dest_shared.value())) {}

  explicit constexpr UnicodeConfig(uint32_t raw_flags) : flags_(raw_flags) {}

  // Predefined convenience constants.
  static constexpr UnicodeConfig kLossyUtf8Unshared() {
    return UnicodeConfig(unibrow::Utf8Variant::kLossyUtf8, SharedFlag{false},
                         SharedFlag{false});
  }
  static constexpr UnicodeConfig kLossyUtf8Shared() {
    return UnicodeConfig(unibrow::Utf8Variant::kLossyUtf8, SharedFlag{true},
                         SharedFlag{true});
  }
  static constexpr UnicodeConfig kWtf16Unshared() {
    return UnicodeConfig(SharedFlag{false}, SharedFlag{false});
  }
  static constexpr UnicodeConfig kWtf16Shared() {
    return UnicodeConfig(SharedFlag{true}, SharedFlag{true});
  }

  constexpr unibrow::Utf8Variant variant() const {
    return VariantField::decode(flags_);
  }
  constexpr bool source_shared() const {
    return SourceSharedField::decode(flags_);
  }
  constexpr bool dest_shared() const { return DestSharedField::decode(flags_); }
  constexpr int32_t raw_as_int() const { return static_cast<int32_t>(flags_); }

 private:
  // When used for WTF16 operations, this field is unused/ignored.
  using VariantField = base::BitField<unibrow::Utf8Variant, 0, 3>;
  // "source shared" indicates whether the source data/array can be concurrently
  // modified and should hence be copied before multiple passes over it can
  // rely on seeing the same bits.
  using SourceSharedField = VariantField::Next<bool, 1>;
  // "dest shared" controls whether the result of the operation should be
  // allocated in shared space.
  using DestSharedField = SourceSharedField::Next<bool, 1>;

  uint32_t flags_ = 0;
};

}  // namespace v8::internal

#endif  // V8_STRINGS_UNICODE_H_