1 // Copyright (c) 2011 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 #ifndef BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_
6 #define BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_
7
8 // Low-level UTF handling functions. Most code will want to use the functions
9 // in utf_string_conversions.h
10
11 #include <stddef.h>
12 #include <stdint.h>
13
14 #include <string>
15
16 namespace base {
17
IsValidCodepoint(uint32_t code_point)18 inline bool IsValidCodepoint(uint32_t code_point) {
19 // Excludes the surrogate code points ([0xD800, 0xDFFF]) and
20 // codepoints larger than 0x10FFFF (the highest codepoint allowed).
21 // Non-characters and unassigned codepoints are allowed.
22 return code_point < 0xD800u ||
23 (code_point >= 0xE000u && code_point <= 0x10FFFFu);
24 }
25
IsValidCharacter(uint32_t code_point)26 inline bool IsValidCharacter(uint32_t code_point) {
27 // Excludes non-characters (U+FDD0..U+FDEF, and all codepoints ending in
28 // 0xFFFE or 0xFFFF) from the set of valid code points.
29 return code_point < 0xD800u ||
30 (code_point >= 0xE000u && code_point < 0xFDD0u) ||
31 (code_point > 0xFDEFu && code_point <= 0x10FFFFu &&
32 (code_point & 0xFFFEu) != 0xFFFEu);
33 }
34
35 // ReadUnicodeCharacter --------------------------------------------------------
36
37 // Reads a UTF-8 stream, placing the next code point into the given output
38 // |*code_point|. |src| represents the entire string to read, and |*char_index|
39 // is the character offset within the string to start reading at. |*char_index|
40 // will be updated to index the last character read, such that incrementing it
41 // (as in a for loop) will take the reader to the next character.
42 //
43 // Returns true on success. On false, |*code_point| will be invalid.
44 bool ReadUnicodeCharacter(const char* src,
45 int32_t src_len,
46 int32_t* char_index,
47 uint32_t* code_point_out);
48
49 // Reads a UTF-16 character. The usage is the same as the 8-bit version above.
50 bool ReadUnicodeCharacter(const char16_t* src,
51 int32_t src_len,
52 int32_t* char_index,
53 uint32_t* code_point);
54
55 // WriteUnicodeCharacter -------------------------------------------------------
56
57 // Appends a UTF-8 character to the given 8-bit string. Returns the number of
58 // bytes written.
59 size_t WriteUnicodeCharacter(uint32_t code_point, std::string* output);
60
61 // Appends the given code point as a UTF-16 character to the given 16-bit
62 // string. Returns the number of 16-bit values written.
63 size_t WriteUnicodeCharacter(uint32_t code_point, std::u16string* output);
64
65 // Generalized Unicode converter -----------------------------------------------
66
67 // Guesses the length of the output in UTF-8 in bytes, clears that output
68 // string, and reserves that amount of space. We assume that the input
69 // character types are unsigned, which will be true for UTF-16 and -32 on our
70 // systems.
71 template <typename CHAR>
72 void PrepareForUTF8Output(const CHAR* src, size_t src_len, std::string* output);
73
74 // Prepares an output buffer (containing either UTF-16 or -32 data) given some
75 // UTF-8 input that will be converted to it. See PrepareForUTF8Output().
76 template <typename STRING>
77 void PrepareForUTF16Or32Output(const char* src, size_t src_len, STRING* output);
78
79 } // namespace base
80
81 #endif // BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_
82