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      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 // This should only be used by the various UTF string conversion files.
      9 
     10 #include "base/base_export.h"
     11 #include "base/strings/string16.h"
     12 
     13 namespace base {
     14 
     15 inline bool IsValidCodepoint(uint32 code_point) {
     16   // Excludes the surrogate code points ([0xD800, 0xDFFF]) and
     17   // codepoints larger than 0x10FFFF (the highest codepoint allowed).
     18   // Non-characters and unassigned codepoints are allowed.
     19   return code_point < 0xD800u ||
     20          (code_point >= 0xE000u && code_point <= 0x10FFFFu);
     21 }
     22 
     23 inline bool IsValidCharacter(uint32 code_point) {
     24   // Excludes non-characters (U+FDD0..U+FDEF, and all codepoints ending in
     25   // 0xFFFE or 0xFFFF) from the set of valid code points.
     26   return code_point < 0xD800u || (code_point >= 0xE000u &&
     27       code_point < 0xFDD0u) || (code_point > 0xFDEFu &&
     28       code_point <= 0x10FFFFu && (code_point & 0xFFFEu) != 0xFFFEu);
     29 }
     30 
     31 // ReadUnicodeCharacter --------------------------------------------------------
     32 
     33 // Reads a UTF-8 stream, placing the next code point into the given output
     34 // |*code_point|. |src| represents the entire string to read, and |*char_index|
     35 // is the character offset within the string to start reading at. |*char_index|
     36 // will be updated to index the last character read, such that incrementing it
     37 // (as in a for loop) will take the reader to the next character.
     38 //
     39 // Returns true on success. On false, |*code_point| will be invalid.
     40 BASE_EXPORT bool ReadUnicodeCharacter(const char* src,
     41                                       int32 src_len,
     42                                       int32* char_index,
     43                                       uint32* code_point_out);
     44 
     45 // Reads a UTF-16 character. The usage is the same as the 8-bit version above.
     46 BASE_EXPORT bool ReadUnicodeCharacter(const char16* src,
     47                                       int32 src_len,
     48                                       int32* char_index,
     49                                       uint32* code_point);
     50 
     51 #if defined(WCHAR_T_IS_UTF32)
     52 // Reads UTF-32 character. The usage is the same as the 8-bit version above.
     53 BASE_EXPORT bool ReadUnicodeCharacter(const wchar_t* src,
     54                                       int32 src_len,
     55                                       int32* char_index,
     56                                       uint32* code_point);
     57 #endif  // defined(WCHAR_T_IS_UTF32)
     58 
     59 // WriteUnicodeCharacter -------------------------------------------------------
     60 
     61 // Appends a UTF-8 character to the given 8-bit string.  Returns the number of
     62 // bytes written.
     63 // TODO(brettw) Bug 79631: This function should not be exposed.
     64 BASE_EXPORT size_t WriteUnicodeCharacter(uint32 code_point,
     65                                          std::string* output);
     66 
     67 // Appends the given code point as a UTF-16 character to the given 16-bit
     68 // string.  Returns the number of 16-bit values written.
     69 BASE_EXPORT size_t WriteUnicodeCharacter(uint32 code_point, string16* output);
     70 
     71 #if defined(WCHAR_T_IS_UTF32)
     72 // Appends the given UTF-32 character to the given 32-bit string.  Returns the
     73 // number of 32-bit values written.
     74 inline size_t WriteUnicodeCharacter(uint32 code_point, std::wstring* output) {
     75   // This is the easy case, just append the character.
     76   output->push_back(code_point);
     77   return 1;
     78 }
     79 #endif  // defined(WCHAR_T_IS_UTF32)
     80 
     81 // Generalized Unicode converter -----------------------------------------------
     82 
     83 // Guesses the length of the output in UTF-8 in bytes, clears that output
     84 // string, and reserves that amount of space.  We assume that the input
     85 // character types are unsigned, which will be true for UTF-16 and -32 on our
     86 // systems.
     87 template<typename CHAR>
     88 void PrepareForUTF8Output(const CHAR* src, size_t src_len, std::string* output);
     89 
     90 // Prepares an output buffer (containing either UTF-16 or -32 data) given some
     91 // UTF-8 input that will be converted to it.  See PrepareForUTF8Output().
     92 template<typename STRING>
     93 void PrepareForUTF16Or32Output(const char* src, size_t src_len, STRING* output);
     94 
     95 }  // namespace base
     96 
     97 #endif  // BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_
     98