utf_string_conversion_utils.cc 4.82 KB
Newer Older
gejun's avatar
gejun committed
1 2 3 4
// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

5
#include "butil/strings/utf_string_conversion_utils.h"
gejun's avatar
gejun committed
6

7
#include "butil/third_party/icu/icu_utf.h"
gejun's avatar
gejun committed
8

9
namespace butil {
gejun's avatar
gejun committed
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147

// ReadUnicodeCharacter --------------------------------------------------------

bool ReadUnicodeCharacter(const char* src,
                          int32_t src_len,
                          int32_t* char_index,
                          uint32_t* code_point_out) {
  // U8_NEXT expects to be able to use -1 to signal an error, so we must
  // use a signed type for code_point.  But this function returns false
  // on error anyway, so code_point_out is unsigned.
  int32_t code_point;
  CBU8_NEXT(src, *char_index, src_len, code_point);
  *code_point_out = static_cast<uint32_t>(code_point);

  // The ICU macro above moves to the next char, we want to point to the last
  // char consumed.
  (*char_index)--;

  // Validate the decoded value.
  return IsValidCodepoint(code_point);
}

bool ReadUnicodeCharacter(const char16* src,
                          int32_t src_len,
                          int32_t* char_index,
                          uint32_t* code_point) {
  if (CBU16_IS_SURROGATE(src[*char_index])) {
    if (!CBU16_IS_SURROGATE_LEAD(src[*char_index]) ||
        *char_index + 1 >= src_len ||
        !CBU16_IS_TRAIL(src[*char_index + 1])) {
      // Invalid surrogate pair.
      return false;
    }

    // Valid surrogate pair.
    *code_point = CBU16_GET_SUPPLEMENTARY(src[*char_index],
                                          src[*char_index + 1]);
    (*char_index)++;
  } else {
    // Not a surrogate, just one 16-bit word.
    *code_point = src[*char_index];
  }

  return IsValidCodepoint(*code_point);
}

#if defined(WCHAR_T_IS_UTF32)
bool ReadUnicodeCharacter(const wchar_t* src,
                          int32_t src_len,
                          int32_t* char_index,
                          uint32_t* code_point) {
  // Conversion is easy since the source is 32-bit.
  *code_point = src[*char_index];

  // Validate the value.
  return IsValidCodepoint(*code_point);
}
#endif  // defined(WCHAR_T_IS_UTF32)

// WriteUnicodeCharacter -------------------------------------------------------

size_t WriteUnicodeCharacter(uint32_t code_point, std::string* output) {
  if (code_point <= 0x7f) {
    // Fast path the common case of one byte.
    output->push_back(code_point);
    return 1;
  }


  // CBU8_APPEND_UNSAFE can append up to 4 bytes.
  size_t char_offset = output->length();
  size_t original_char_offset = char_offset;
  output->resize(char_offset + CBU8_MAX_LENGTH);

  CBU8_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);

  // CBU8_APPEND_UNSAFE will advance our pointer past the inserted character, so
  // it will represent the new length of the string.
  output->resize(char_offset);
  return char_offset - original_char_offset;
}

size_t WriteUnicodeCharacter(uint32_t code_point, string16* output) {
  if (CBU16_LENGTH(code_point) == 1) {
    // Thie code point is in the Basic Multilingual Plane (BMP).
    output->push_back(static_cast<char16>(code_point));
    return 1;
  }
  // Non-BMP characters use a double-character encoding.
  size_t char_offset = output->length();
  output->resize(char_offset + CBU16_MAX_LENGTH);
  CBU16_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
  return CBU16_MAX_LENGTH;
}

// Generalized Unicode converter -----------------------------------------------

template<typename CHAR>
void PrepareForUTF8Output(const CHAR* src,
                          size_t src_len,
                          std::string* output) {
  output->clear();
  if (src_len == 0)
    return;
  if (src[0] < 0x80) {
    // Assume that the entire input will be ASCII.
    output->reserve(src_len);
  } else {
    // Assume that the entire input is non-ASCII and will have 3 bytes per char.
    output->reserve(src_len * 3);
  }
}

// Instantiate versions we know callers will need.
template void PrepareForUTF8Output(const wchar_t*, size_t, std::string*);
template void PrepareForUTF8Output(const char16*, size_t, std::string*);

template<typename STRING>
void PrepareForUTF16Or32Output(const char* src,
                               size_t src_len,
                               STRING* output) {
  output->clear();
  if (src_len == 0)
    return;
  if (static_cast<unsigned char>(src[0]) < 0x80) {
    // Assume the input is all ASCII, which means 1:1 correspondence.
    output->reserve(src_len);
  } else {
    // Otherwise assume that the UTF-8 sequences will have 2 bytes for each
    // character.
    output->reserve(src_len / 2);
  }
}

// Instantiate versions we know callers will need.
template void PrepareForUTF16Or32Output(const char*, size_t, std::wstring*);
template void PrepareForUTF16Or32Output(const char*, size_t, string16*);

148
}  // namespace butil