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/utf_string_conversion_utils.h"
6
7#include "base/third_party/icu/icu_utf.h"
8
9namespace base {
10
11// ReadUnicodeCharacter --------------------------------------------------------
12
13bool ReadUnicodeCharacter(const char* src,
14                          int32 src_len,
15                          int32* char_index,
16                          uint32* code_point_out) {
17  // U8_NEXT expects to be able to use -1 to signal an error, so we must
18  // use a signed type for code_point.  But this function returns false
19  // on error anyway, so code_point_out is unsigned.
20  int32 code_point;
21  CBU8_NEXT(src, *char_index, src_len, code_point);
22  *code_point_out = static_cast<uint32>(code_point);
23
24  // The ICU macro above moves to the next char, we want to point to the last
25  // char consumed.
26  (*char_index)--;
27
28  // Validate the decoded value.
29  return IsValidCodepoint(code_point);
30}
31
32bool ReadUnicodeCharacter(const char16* src,
33                          int32 src_len,
34                          int32* char_index,
35                          uint32* code_point) {
36  if (CBU16_IS_SURROGATE(src[*char_index])) {
37    if (!CBU16_IS_SURROGATE_LEAD(src[*char_index]) ||
38        *char_index + 1 >= src_len ||
39        !CBU16_IS_TRAIL(src[*char_index + 1])) {
40      // Invalid surrogate pair.
41      return false;
42    }
43
44    // Valid surrogate pair.
45    *code_point = CBU16_GET_SUPPLEMENTARY(src[*char_index],
46                                          src[*char_index + 1]);
47    (*char_index)++;
48  } else {
49    // Not a surrogate, just one 16-bit word.
50    *code_point = src[*char_index];
51  }
52
53  return IsValidCodepoint(*code_point);
54}
55
56#if defined(WCHAR_T_IS_UTF32)
57bool ReadUnicodeCharacter(const wchar_t* src,
58                          int32 src_len,
59                          int32* char_index,
60                          uint32* code_point) {
61  // Conversion is easy since the source is 32-bit.
62  *code_point = src[*char_index];
63
64  // Validate the value.
65  return IsValidCodepoint(*code_point);
66}
67#endif  // defined(WCHAR_T_IS_UTF32)
68
69// WriteUnicodeCharacter -------------------------------------------------------
70
71size_t WriteUnicodeCharacter(uint32 code_point, std::string* output) {
72  if (code_point <= 0x7f) {
73    // Fast path the common case of one byte.
74    output->push_back(code_point);
75    return 1;
76  }
77
78
79  // CBU8_APPEND_UNSAFE can append up to 4 bytes.
80  size_t char_offset = output->length();
81  size_t original_char_offset = char_offset;
82  output->resize(char_offset + CBU8_MAX_LENGTH);
83
84  CBU8_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
85
86  // CBU8_APPEND_UNSAFE will advance our pointer past the inserted character, so
87  // it will represent the new length of the string.
88  output->resize(char_offset);
89  return char_offset - original_char_offset;
90}
91
92size_t WriteUnicodeCharacter(uint32 code_point, string16* output) {
93  if (CBU16_LENGTH(code_point) == 1) {
94    // Thie code point is in the Basic Multilingual Plane (BMP).
95    output->push_back(static_cast<char16>(code_point));
96    return 1;
97  }
98  // Non-BMP characters use a double-character encoding.
99  size_t char_offset = output->length();
100  output->resize(char_offset + CBU16_MAX_LENGTH);
101  CBU16_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
102  return CBU16_MAX_LENGTH;
103}
104
105// Generalized Unicode converter -----------------------------------------------
106
107template<typename CHAR>
108void PrepareForUTF8Output(const CHAR* src,
109                          size_t src_len,
110                          std::string* output) {
111  output->clear();
112  if (src_len == 0)
113    return;
114  if (src[0] < 0x80) {
115    // Assume that the entire input will be ASCII.
116    output->reserve(src_len);
117  } else {
118    // Assume that the entire input is non-ASCII and will have 3 bytes per char.
119    output->reserve(src_len * 3);
120  }
121}
122
123// Instantiate versions we know callers will need.
124template void PrepareForUTF8Output(const wchar_t*, size_t, std::string*);
125template void PrepareForUTF8Output(const char16*, size_t, std::string*);
126
127template<typename STRING>
128void PrepareForUTF16Or32Output(const char* src,
129                               size_t src_len,
130                               STRING* output) {
131  output->clear();
132  if (src_len == 0)
133    return;
134  if (static_cast<unsigned char>(src[0]) < 0x80) {
135    // Assume the input is all ASCII, which means 1:1 correspondence.
136    output->reserve(src_len);
137  } else {
138    // Otherwise assume that the UTF-8 sequences will have 2 bytes for each
139    // character.
140    output->reserve(src_len / 2);
141  }
142}
143
144// Instantiate versions we know callers will need.
145template void PrepareForUTF16Or32Output(const char*, size_t, std::wstring*);
146template void PrepareForUTF16Or32Output(const char*, size_t, string16*);
147
148}  // namespace base
149