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      1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "base/strings/utf_string_conversion_utils.h"
      6 
      7 #include "base/third_party/icu/icu_utf.h"
      8 #include "build/build_config.h"
      9 
     10 namespace base {
     11 
     12 // ReadUnicodeCharacter --------------------------------------------------------
     13 
     14 bool ReadUnicodeCharacter(const char* src,
     15                           int32_t src_len,
     16                           int32_t* char_index,
     17                           uint32_t* code_point_out) {
     18   // U8_NEXT expects to be able to use -1 to signal an error, so we must
     19   // use a signed type for code_point.  But this function returns false
     20   // on error anyway, so code_point_out is unsigned.
     21   int32_t code_point;
     22   CBU8_NEXT(src, *char_index, src_len, code_point);
     23   *code_point_out = static_cast<uint32_t>(code_point);
     24 
     25   // The ICU macro above moves to the next char, we want to point to the last
     26   // char consumed.
     27   (*char_index)--;
     28 
     29   // Validate the decoded value.
     30   return IsValidCodepoint(code_point);
     31 }
     32 
     33 bool ReadUnicodeCharacter(const char16* src,
     34                           int32_t src_len,
     35                           int32_t* char_index,
     36                           uint32_t* code_point) {
     37   if (CBU16_IS_SURROGATE(src[*char_index])) {
     38     if (!CBU16_IS_SURROGATE_LEAD(src[*char_index]) ||
     39         *char_index + 1 >= src_len ||
     40         !CBU16_IS_TRAIL(src[*char_index + 1])) {
     41       // Invalid surrogate pair.
     42       return false;
     43     }
     44 
     45     // Valid surrogate pair.
     46     *code_point = CBU16_GET_SUPPLEMENTARY(src[*char_index],
     47                                           src[*char_index + 1]);
     48     (*char_index)++;
     49   } else {
     50     // Not a surrogate, just one 16-bit word.
     51     *code_point = src[*char_index];
     52   }
     53 
     54   return IsValidCodepoint(*code_point);
     55 }
     56 
     57 #if defined(WCHAR_T_IS_UTF32)
     58 bool ReadUnicodeCharacter(const wchar_t* src,
     59                           int32_t src_len,
     60                           int32_t* char_index,
     61                           uint32_t* code_point) {
     62   // Conversion is easy since the source is 32-bit.
     63   *code_point = src[*char_index];
     64 
     65   // Validate the value.
     66   return IsValidCodepoint(*code_point);
     67 }
     68 #endif  // defined(WCHAR_T_IS_UTF32)
     69 
     70 // WriteUnicodeCharacter -------------------------------------------------------
     71 
     72 size_t WriteUnicodeCharacter(uint32_t code_point, std::string* output) {
     73   if (code_point <= 0x7f) {
     74     // Fast path the common case of one byte.
     75     output->push_back(static_cast<char>(code_point));
     76     return 1;
     77   }
     78 
     79 
     80   // CBU8_APPEND_UNSAFE can append up to 4 bytes.
     81   size_t char_offset = output->length();
     82   size_t original_char_offset = char_offset;
     83   output->resize(char_offset + CBU8_MAX_LENGTH);
     84 
     85   CBU8_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
     86 
     87   // CBU8_APPEND_UNSAFE will advance our pointer past the inserted character, so
     88   // it will represent the new length of the string.
     89   output->resize(char_offset);
     90   return char_offset - original_char_offset;
     91 }
     92 
     93 size_t WriteUnicodeCharacter(uint32_t code_point, string16* output) {
     94   if (CBU16_LENGTH(code_point) == 1) {
     95     // Thie code point is in the Basic Multilingual Plane (BMP).
     96     output->push_back(static_cast<char16>(code_point));
     97     return 1;
     98   }
     99   // Non-BMP characters use a double-character encoding.
    100   size_t char_offset = output->length();
    101   output->resize(char_offset + CBU16_MAX_LENGTH);
    102   CBU16_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
    103   return CBU16_MAX_LENGTH;
    104 }
    105 
    106 // Generalized Unicode converter -----------------------------------------------
    107 
    108 template<typename CHAR>
    109 void PrepareForUTF8Output(const CHAR* src,
    110                           size_t src_len,
    111                           std::string* output) {
    112   output->clear();
    113   if (src_len == 0)
    114     return;
    115   if (src[0] < 0x80) {
    116     // Assume that the entire input will be ASCII.
    117     output->reserve(src_len);
    118   } else {
    119     // Assume that the entire input is non-ASCII and will have 3 bytes per char.
    120     output->reserve(src_len * 3);
    121   }
    122 }
    123 
    124 // Instantiate versions we know callers will need.
    125 #if !defined(OS_WIN)
    126 // wchar_t and char16 are the same thing on Windows.
    127 template void PrepareForUTF8Output(const wchar_t*, size_t, std::string*);
    128 #endif
    129 template void PrepareForUTF8Output(const char16*, size_t, std::string*);
    130 
    131 template<typename STRING>
    132 void PrepareForUTF16Or32Output(const char* src,
    133                                size_t src_len,
    134                                STRING* output) {
    135   output->clear();
    136   if (src_len == 0)
    137     return;
    138   if (static_cast<unsigned char>(src[0]) < 0x80) {
    139     // Assume the input is all ASCII, which means 1:1 correspondence.
    140     output->reserve(src_len);
    141   } else {
    142     // Otherwise assume that the UTF-8 sequences will have 2 bytes for each
    143     // character.
    144     output->reserve(src_len / 2);
    145   }
    146 }
    147 
    148 // Instantiate versions we know callers will need.
    149 #if !defined(OS_WIN)
    150 // std::wstring and string16 are the same thing on Windows.
    151 template void PrepareForUTF16Or32Output(const char*, size_t, std::wstring*);
    152 #endif
    153 template void PrepareForUTF16Or32Output(const char*, size_t, string16*);
    154 
    155 }  // namespace base
    156