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 // Copyright (c) 2011 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.

 #ifndef BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_

 #define BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_

 // This should only be used by the various UTF string conversion files.

 #include "base/base_export.h"

 #include "base/strings/string16.h"

 namespace base {

 inline bool IsValidCodepoint(uint32 code_point) {

   // Excludes the surrogate code points ([0xD800, 0xDFFF]) and

   // codepoints larger than 0x10FFFF (the highest codepoint allowed).

   // Non-characters and unassigned codepoints are allowed.

   return code_point < 0xD800u ||

          (code_point >= 0xE000u && code_point <= 0x10FFFFu);

 }

 inline bool IsValidCharacter(uint32 code_point) {

   // Excludes non-characters (U+FDD0..U+FDEF, and all codepoints ending in

   // 0xFFFE or 0xFFFF) from the set of valid code points.

   return code_point < 0xD800u || (code_point >= 0xE000u &&

       code_point < 0xFDD0u) || (code_point > 0xFDEFu &&

       code_point <= 0x10FFFFu && (code_point & 0xFFFEu) != 0xFFFEu);

 }

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

 // Reads a UTF-8 stream, placing the next code point into the given output

 // |*code_point|. |src| represents the entire string to read, and |*char_index|

 // is the character offset within the string to start reading at. |*char_index|

 // will be updated to index the last character read, such that incrementing it

 // (as in a for loop) will take the reader to the next character.

 //

 // Returns true on success. On false, |*code_point| will be invalid.

 BASE_EXPORT bool ReadUnicodeCharacter(const char* src,

                                       int32 src_len,

                                       int32* char_index,

                                       uint32* code_point_out);

 // Reads a UTF-16 character. The usage is the same as the 8-bit version above.

 BASE_EXPORT bool ReadUnicodeCharacter(const char16* src,

                                       int32 src_len,

                                       int32* char_index,

                                       uint32* code_point);

 #if defined(WCHAR_T_IS_UTF32)

 // Reads UTF-32 character. The usage is the same as the 8-bit version above.

 BASE_EXPORT bool ReadUnicodeCharacter(const wchar_t* src,

                                       int32 src_len,

                                       int32* char_index,

                                       uint32* code_point);

 #endif  // defined(WCHAR_T_IS_UTF32)

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

 // Appends a UTF-8 character to the given 8-bit string.  Returns the number of

 // bytes written.

 // TODO(brettw) Bug 79631: This function should not be exposed.

 BASE_EXPORT size_t WriteUnicodeCharacter(uint32 code_point,

                                          std::string* output);

 // Appends the given code point as a UTF-16 character to the given 16-bit

 // string.  Returns the number of 16-bit values written.

 BASE_EXPORT size_t WriteUnicodeCharacter(uint32 code_point, string16* output);

 #if defined(WCHAR_T_IS_UTF32)

 // Appends the given UTF-32 character to the given 32-bit string.  Returns the

 // number of 32-bit values written.

 inline size_t WriteUnicodeCharacter(uint32 code_point, std::wstring* output) {

   // This is the easy case, just append the character.

   output->push_back(code_point);

   return 1;

 }

 #endif  // defined(WCHAR_T_IS_UTF32)

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

 // Guesses the length of the output in UTF-8 in bytes, clears that output

 // string, and reserves that amount of space.  We assume that the input

 // character types are unsigned, which will be true for UTF-16 and -32 on our

 // systems.

 template<typename CHAR>

 void PrepareForUTF8Output(const CHAR* src, size_t src_len, std::string* output);

 // Prepares an output buffer (containing either UTF-16 or -32 data) given some

 // UTF-8 input that will be converted to it.  See PrepareForUTF8Output().

 template<typename STRING>

 void PrepareForUTF16Or32Output(const char* src, size_t src_len, STRING* output);

 }  // namespace base

 #endif  // BASE_STRINGS_UTF_STRING_CONVERSION_UTILS_H_