Move the ICU string conversions into its own file. This new file is included

from the old string_util to avoid changing any callers at this time.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/257032

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27914 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 727 insertions, 0 deletions

diff --git a/base/i18n/string_conversions.cc b/base/i18n/string_conversions.cc
new file mode 100644
index 0000000..35c9d6d
--- /dev/null
+++ b/base/i18n/string_conversions.cc
@@ -0,0 +1,626 @@
+// Copyright (c) 2009 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.
+
+#include "base/i18n/string_conversions.h"
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/string_util.h"
+#include "unicode/ucnv.h"
+#include "unicode/ucnv_cb.h"
+#include "unicode/ucnv_err.h"
+#include "unicode/ustring.h"
+
+namespace {
+
+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);
+}
+
+// ToUnicodeCallbackSubstitute() is based on UCNV_TO_U_CALLBACK_SUSBSTITUTE
+// in source/common/ucnv_err.c.
+
+// Copyright (c) 1995-2006 International Business Machines Corporation
+// and others
+//
+// All rights reserved.
+//
+
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, and/or
+// sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, provided that the above copyright notice(s) and
+// this permission notice appear in all copies of the Software and that
+// both the above copyright notice(s) and this permission notice appear in
+// supporting documentation.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+// OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS
+// INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT
+// OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+// OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE
+// OR PERFORMANCE OF THIS SOFTWARE.
+//
+// Except as contained in this notice, the name of a copyright holder
+// shall not be used in advertising or otherwise to promote the sale, use
+// or other dealings in this Software without prior written authorization
+// of the copyright holder.
+
+//  ___________________________________________________________________________
+//
+// All trademarks and registered trademarks mentioned herein are the property
+// of their respective owners.
+
+void ToUnicodeCallbackSubstitute(const void* context,
+                                 UConverterToUnicodeArgs *to_args,
+                                 const char* code_units,
+                                 int32_t length,
+                                 UConverterCallbackReason reason,
+                                 UErrorCode * err) {
+  static const UChar kReplacementChar = 0xFFFD;
+  if (reason <= UCNV_IRREGULAR) {
+      if (context == NULL ||
+          (*(reinterpret_cast<const char*>(context)) == 'i' &&
+           reason == UCNV_UNASSIGNED)) {
+        *err = U_ZERO_ERROR;
+        ucnv_cbToUWriteUChars(to_args, &kReplacementChar, 1, 0, err);
+      }
+      // else the caller must have set the error code accordingly.
+  }
+  // else ignore the reset, close and clone calls.
+}
+
+// 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.
+bool ReadUnicodeCharacter(const char* src, int32 src_len,
+                          int32* char_index, uint32* code_point_out) {
+  // U8_NEXT expects to be able to use -1 to signal an error, so we must
+  // use a signed type for code_point.  But this function returns false
+  // on error anyway, so code_point_out is unsigned.
+  int32 code_point;
+  U8_NEXT(src, *char_index, src_len, code_point);
+  *code_point_out = static_cast<uint32>(code_point);
+
+  // The ICU macro above moves to the next char, we want to point to the last
+  // char consumed.
+  (*char_index)--;
+
+  // Validate the decoded value.
+  return IsValidCodepoint(code_point);
+}
+
+// Reads a UTF-16 character. The usage is the same as the 8-bit version above.
+bool ReadUnicodeCharacter(const char16* src, int32 src_len,
+                          int32* char_index, uint32* code_point) {
+  if (U16_IS_SURROGATE(src[*char_index])) {
+    if (!U16_IS_SURROGATE_LEAD(src[*char_index]) ||
+        *char_index + 1 >= src_len ||
+        !U16_IS_TRAIL(src[*char_index + 1])) {
+      // Invalid surrogate pair.
+      return false;
+    }
+
+    // Valid surrogate pair.
+    *code_point = U16_GET_SUPPLEMENTARY(src[*char_index],
+                                        src[*char_index + 1]);
+    (*char_index)++;
+  } else {
+    // Not a surrogate, just one 16-bit word.
+    *code_point = src[*char_index];
+  }
+
+  return IsValidCodepoint(*code_point);
+}
+
+#if defined(WCHAR_T_IS_UTF32)
+// Reads UTF-32 character. The usage is the same as the 8-bit version above.
+bool ReadUnicodeCharacter(const wchar_t* src, int32 src_len,
+                          int32* char_index, uint32* code_point) {
+  // Conversion is easy since the source is 32-bit.
+  *code_point = src[*char_index];
+
+  // Validate the value.
+  return IsValidCodepoint(*code_point);
+}
+#endif  // defined(WCHAR_T_IS_UTF32)
+
+// WriteUnicodeCharacter -------------------------------------------------------
+
+// Appends a UTF-8 character to the given 8-bit string.
+void WriteUnicodeCharacter(uint32 code_point, std::string* output) {
+  if (code_point <= 0x7f) {
+    // Fast path the common case of one byte.
+    output->push_back(code_point);
+    return;
+  }
+
+  // U8_APPEND_UNSAFE can append up to 4 bytes.
+  int32 char_offset = static_cast<int32>(output->length());
+  output->resize(char_offset + U8_MAX_LENGTH);
+
+  U8_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
+
+  // U8_APPEND_UNSAFE will advance our pointer past the inserted character, so
+  // it will represent the new length of the string.
+  output->resize(char_offset);
+}
+
+// Appends the given code point as a UTF-16 character to the STL string.
+void WriteUnicodeCharacter(uint32 code_point, string16* output) {
+  if (U16_LENGTH(code_point) == 1) {
+    // Thie code point is in the Basic Multilingual Plane (BMP).
+    output->push_back(static_cast<char16>(code_point));
+  } else {
+    // Non-BMP characters use a double-character encoding.
+    int32 char_offset = static_cast<int32>(output->length());
+    output->resize(char_offset + U16_MAX_LENGTH);
+    U16_APPEND_UNSAFE(&(*output)[0], char_offset, code_point);
+  }
+}
+
+#if defined(WCHAR_T_IS_UTF32)
+// Appends the given UTF-32 character to the given 32-bit string.
+inline void WriteUnicodeCharacter(uint32 code_point, std::wstring* output) {
+  // This is the easy case, just append the character.
+  output->push_back(code_point);
+}
+#endif  // defined(WCHAR_T_IS_UTF32)
+
+// Generalized Unicode converter -----------------------------------------------
+
+// Converts the given source Unicode character type to the given destination
+// Unicode character type as a STL string. The given input buffer and size
+// determine the source, and the given output STL string will be replaced by
+// the result.
+template<typename SRC_CHAR, typename DEST_STRING>
+bool ConvertUnicode(const SRC_CHAR* src, size_t src_len, DEST_STRING* output) {
+  output->clear();
+
+  // ICU requires 32-bit numbers.
+  bool success = true;
+  int32 src_len32 = static_cast<int32>(src_len);
+  for (int32 i = 0; i < src_len32; i++) {
+    uint32 code_point;
+    if (ReadUnicodeCharacter(src, src_len32, &i, &code_point)) {
+      WriteUnicodeCharacter(code_point, output);
+    } else {
+      // TODO(jungshik): consider adding 'Replacement character' (U+FFFD)
+      // in place of an invalid codepoint.
+      success = false;
+    }
+  }
+  return success;
+}
+
+
+// Guesses the length of the output in UTF-8 in bytes, and reserves that amount
+// of space in the given string. We also assume that the input character types
+// are unsigned, which will be true for UTF-16 and -32 on our systems. We assume
+// the string length is greater than zero.
+template<typename CHAR>
+void ReserveUTF8Output(const CHAR* src, size_t src_len, std::string* output) {
+  if (src[0] < 0x80) {
+    // Assume that the entire input will be ASCII.
+    output->reserve(src_len);
+  } else {
+    // Assume that the entire input is non-ASCII and will have 3 bytes per char.
+    output->reserve(src_len * 3);
+  }
+}
+
+// Guesses the size of the output buffer (containing either UTF-16 or -32 data)
+// given some UTF-8 input that will be converted to it. See ReserveUTF8Output.
+// We assume the source length is > 0.
+template<typename STRING>
+void ReserveUTF16Or32Output(const char* src, size_t src_len, STRING* output) {
+  if (static_cast<unsigned char>(src[0]) < 0x80) {
+    // Assume the input is all ASCII, which means 1:1 correspondence.
+    output->reserve(src_len);
+  } else {
+    // Otherwise assume that the UTF-8 sequences will have 2 bytes for each
+    // character.
+    output->reserve(src_len / 2);
+  }
+}
+
+bool ConvertFromUTF16(UConverter* converter, const UChar* uchar_src,
+                      int uchar_len, OnStringUtilConversionError::Type on_error,
+                      std::string* encoded) {
+  int encoded_max_length = UCNV_GET_MAX_BYTES_FOR_STRING(uchar_len,
+      ucnv_getMaxCharSize(converter));
+  encoded->resize(encoded_max_length);
+
+  UErrorCode status = U_ZERO_ERROR;
+
+  // Setup our error handler.
+  switch (on_error) {
+    case OnStringUtilConversionError::FAIL:
+      ucnv_setFromUCallBack(converter, UCNV_FROM_U_CALLBACK_STOP, 0,
+                            NULL, NULL, &status);
+      break;
+    case OnStringUtilConversionError::SKIP:
+    case OnStringUtilConversionError::SUBSTITUTE:
+      ucnv_setFromUCallBack(converter, UCNV_FROM_U_CALLBACK_SKIP, 0,
+                            NULL, NULL, &status);
+      break;
+    default:
+      NOTREACHED();
+  }
+
+  // ucnv_fromUChars returns size not including terminating null
+  int actual_size = ucnv_fromUChars(converter, &(*encoded)[0],
+      encoded_max_length, uchar_src, uchar_len, &status);
+  encoded->resize(actual_size);
+  ucnv_close(converter);
+  if (U_SUCCESS(status))
+    return true;
+  encoded->clear();  // Make sure the output is empty on error.
+  return false;
+}
+
+// Set up our error handler for ToUTF-16 converters
+void SetUpErrorHandlerForToUChars(OnStringUtilConversionError::Type on_error,
+                                  UConverter* converter, UErrorCode* status) {
+  switch (on_error) {
+    case OnStringUtilConversionError::FAIL:
+      ucnv_setToUCallBack(converter, UCNV_TO_U_CALLBACK_STOP, 0,
+                          NULL, NULL, status);
+      break;
+    case OnStringUtilConversionError::SKIP:
+      ucnv_setToUCallBack(converter, UCNV_TO_U_CALLBACK_SKIP, 0,
+                          NULL, NULL, status);
+      break;
+    case OnStringUtilConversionError::SUBSTITUTE:
+      ucnv_setToUCallBack(converter, ToUnicodeCallbackSubstitute, 0,
+                          NULL, NULL, status);
+      break;
+    default:
+      NOTREACHED();
+  }
+}
+
+inline UConverterType utf32_platform_endian() {
+#if U_IS_BIG_ENDIAN
+  return UCNV_UTF32_BigEndian;
+#else
+  return UCNV_UTF32_LittleEndian;
+#endif
+}
+
+}  // namespace
+
+// UTF-8 <-> Wide --------------------------------------------------------------
+
+std::string WideToUTF8(const std::wstring& wide) {
+  std::string ret;
+  if (wide.empty())
+    return ret;
+
+  // Ignore the success flag of this call, it will do the best it can for
+  // invalid input, which is what we want here.
+  WideToUTF8(wide.data(), wide.length(), &ret);
+  return ret;
+}
+
+bool WideToUTF8(const wchar_t* src, size_t src_len, std::string* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  ReserveUTF8Output(src, src_len, output);
+  return ConvertUnicode<wchar_t, std::string>(src, src_len, output);
+}
+
+std::wstring UTF8ToWide(const base::StringPiece& utf8) {
+  std::wstring ret;
+  if (utf8.empty())
+    return ret;
+
+  UTF8ToWide(utf8.data(), utf8.length(), &ret);
+  return ret;
+}
+
+bool UTF8ToWide(const char* src, size_t src_len, std::wstring* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  ReserveUTF16Or32Output(src, src_len, output);
+  return ConvertUnicode<char, std::wstring>(src, src_len, output);
+}
+
+// UTF-16 <-> Wide -------------------------------------------------------------
+
+#if defined(WCHAR_T_IS_UTF16)
+
+// When wide == UTF-16, then conversions are a NOP.
+string16 WideToUTF16(const std::wstring& wide) {
+  return wide;
+}
+
+bool WideToUTF16(const wchar_t* src, size_t src_len, string16* output) {
+  output->assign(src, src_len);
+  return true;
+}
+
+std::wstring UTF16ToWide(const string16& utf16) {
+  return utf16;
+}
+
+bool UTF16ToWide(const char16* src, size_t src_len, std::wstring* output) {
+  output->assign(src, src_len);
+  return true;
+}
+
+#elif defined(WCHAR_T_IS_UTF32)
+
+string16 WideToUTF16(const std::wstring& wide) {
+  string16 ret;
+  if (wide.empty())
+    return ret;
+
+  WideToUTF16(wide.data(), wide.length(), &ret);
+  return ret;
+}
+
+bool WideToUTF16(const wchar_t* src, size_t src_len, string16* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  // Assume that normally we won't have any non-BMP characters so the counts
+  // will be the same.
+  output->reserve(src_len);
+  return ConvertUnicode<wchar_t, string16>(src, src_len, output);
+}
+
+std::wstring UTF16ToWide(const string16& utf16) {
+  std::wstring ret;
+  if (utf16.empty())
+    return ret;
+
+  UTF16ToWide(utf16.data(), utf16.length(), &ret);
+  return ret;
+}
+
+bool UTF16ToWide(const char16* src, size_t src_len, std::wstring* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  // Assume that normally we won't have any non-BMP characters so the counts
+  // will be the same.
+  output->reserve(src_len);
+  return ConvertUnicode<char16, std::wstring>(src, src_len, output);
+}
+
+#endif  // defined(WCHAR_T_IS_UTF32)
+
+// UTF16 <-> UTF8 --------------------------------------------------------------
+
+#if defined(WCHAR_T_IS_UTF32)
+
+bool UTF8ToUTF16(const char* src, size_t src_len, string16* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  ReserveUTF16Or32Output(src, src_len, output);
+  return ConvertUnicode<char, string16>(src, src_len, output);
+}
+
+string16 UTF8ToUTF16(const std::string& utf8) {
+  string16 ret;
+  if (utf8.empty())
+    return ret;
+
+  // Ignore the success flag of this call, it will do the best it can for
+  // invalid input, which is what we want here.
+  UTF8ToUTF16(utf8.data(), utf8.length(), &ret);
+  return ret;
+}
+
+bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output) {
+  if (src_len == 0) {
+    output->clear();
+    return true;
+  }
+
+  ReserveUTF8Output(src, src_len, output);
+  return ConvertUnicode<char16, std::string>(src, src_len, output);
+}
+
+std::string UTF16ToUTF8(const string16& utf16) {
+  std::string ret;
+  if (utf16.empty())
+    return ret;
+
+  // Ignore the success flag of this call, it will do the best it can for
+  // invalid input, which is what we want here.
+  UTF16ToUTF8(utf16.data(), utf16.length(), &ret);
+  return ret;
+}
+
+#elif defined(WCHAR_T_IS_UTF16)
+// Easy case since we can use the "wide" versions we already wrote above.
+
+bool UTF8ToUTF16(const char* src, size_t src_len, string16* output) {
+  return UTF8ToWide(src, src_len, output);
+}
+
+string16 UTF8ToUTF16(const std::string& utf8) {
+  return UTF8ToWide(utf8);
+}
+
+bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output) {
+  return WideToUTF8(src, src_len, output);
+}
+
+std::string UTF16ToUTF8(const string16& utf16) {
+  return WideToUTF8(utf16);
+}
+
+#endif
+
+// Codepage <-> Wide/UTF-16  ---------------------------------------------------
+
+// Convert a wstring into the specified codepage_name.  If the codepage
+// isn't found, return false.
+bool WideToCodepage(const std::wstring& wide,
+                    const char* codepage_name,
+                    OnStringUtilConversionError::Type on_error,
+                    std::string* encoded) {
+#if defined(WCHAR_T_IS_UTF16)
+  return UTF16ToCodepage(wide, codepage_name, on_error, encoded);
+#elif defined(WCHAR_T_IS_UTF32)
+  encoded->clear();
+
+  UErrorCode status = U_ZERO_ERROR;
+  UConverter* converter = ucnv_open(codepage_name, &status);
+  if (!U_SUCCESS(status))
+    return false;
+
+  int utf16_len;
+  // When wchar_t is wider than UChar (16 bits), transform |wide| into a
+  // UChar* string.  Size the UChar* buffer to be large enough to hold twice
+  // as many UTF-16 code units (UChar's) as there are Unicode code points,
+  // in case each code points translates to a UTF-16 surrogate pair,
+  // and leave room for a NUL terminator.
+  std::vector<UChar> utf16(wide.length() * 2 + 1);
+  u_strFromWCS(&utf16[0], utf16.size(), &utf16_len,
+               wide.c_str(), wide.length(), &status);
+  DCHECK(U_SUCCESS(status)) << "failed to convert wstring to UChar*";
+
+  return ConvertFromUTF16(converter, &utf16[0], utf16_len, on_error, encoded);
+#endif  // defined(WCHAR_T_IS_UTF32)
+}
+
+// Convert a UTF-16 string into the specified codepage_name.  If the codepage
+// isn't found, return false.
+bool UTF16ToCodepage(const string16& utf16,
+                    const char* codepage_name,
+                    OnStringUtilConversionError::Type on_error,
+                    std::string* encoded) {
+  encoded->clear();
+
+  UErrorCode status = U_ZERO_ERROR;
+  UConverter* converter = ucnv_open(codepage_name, &status);
+  if (!U_SUCCESS(status))
+    return false;
+
+  return ConvertFromUTF16(converter, utf16.c_str(),
+                          static_cast<int>(utf16.length()), on_error, encoded);
+}
+
+// Converts a string of the given codepage into wstring.
+// If the codepage isn't found, return false.
+bool CodepageToWide(const std::string& encoded,
+                    const char* codepage_name,
+                    OnStringUtilConversionError::Type on_error,
+                    std::wstring* wide) {
+#if defined(WCHAR_T_IS_UTF16)
+  return CodepageToUTF16(encoded, codepage_name, on_error, wide);
+#elif defined(WCHAR_T_IS_UTF32)
+  wide->clear();
+
+  UErrorCode status = U_ZERO_ERROR;
+  UConverter* converter = ucnv_open(codepage_name, &status);
+  if (!U_SUCCESS(status))
+    return false;
+
+  // The maximum length in 4 byte unit of UTF-32 output would be
+  // at most the same as the number of bytes in input. In the worst
+  // case of GB18030 (excluding escaped-based encodings like ISO-2022-JP),
+  // this can be 4 times larger than actually needed.
+  size_t wchar_max_length = encoded.length() + 1;
+
+  // The byte buffer and its length to pass to ucnv_toAlgorithimic.
+  char* byte_buffer = reinterpret_cast<char*>(
+      WriteInto(wide, wchar_max_length));
+  int byte_buffer_length = static_cast<int>(wchar_max_length) * 4;
+
+  SetUpErrorHandlerForToUChars(on_error, converter, &status);
+  int actual_size = ucnv_toAlgorithmic(utf32_platform_endian(),
+                                       converter,
+                                       byte_buffer,
+                                       byte_buffer_length,
+                                       encoded.data(),
+                                       static_cast<int>(encoded.length()),
+                                       &status);
+  ucnv_close(converter);
+
+  if (!U_SUCCESS(status)) {
+    wide->clear();  // Make sure the output is empty on error.
+    return false;
+  }
+
+  // actual_size is # of bytes.
+  wide->resize(actual_size / 4);
+  return true;
+#endif  // defined(WCHAR_T_IS_UTF32)
+}
+
+// Converts a string of the given codepage into UTF-16.
+// If the codepage isn't found, return false.
+bool CodepageToUTF16(const std::string& encoded,
+                     const char* codepage_name,
+                     OnStringUtilConversionError::Type on_error,
+                     string16* utf16) {
+  utf16->clear();
+
+  UErrorCode status = U_ZERO_ERROR;
+  UConverter* converter = ucnv_open(codepage_name, &status);
+  if (!U_SUCCESS(status))
+    return false;
+
+  // Even in the worst case, the maximum length in 2-byte units of UTF-16
+  // output would be at most the same as the number of bytes in input. There
+  // is no single-byte encoding in which a character is mapped to a
+  // non-BMP character requiring two 2-byte units.
+  //
+  // Moreover, non-BMP characters in legacy multibyte encodings
+  // (e.g. EUC-JP, GB18030) take at least 2 bytes. The only exceptions are
+  // BOCU and SCSU, but we don't care about them.
+  size_t uchar_max_length = encoded.length() + 1;
+
+  SetUpErrorHandlerForToUChars(on_error, converter, &status);
+  int actual_size = ucnv_toUChars(converter,
+                                  WriteInto(utf16, uchar_max_length),
+                                  static_cast<int>(uchar_max_length),
+                                  encoded.data(),
+                                  static_cast<int>(encoded.length()),
+                                  &status);
+  ucnv_close(converter);
+  if (!U_SUCCESS(status)) {
+    utf16->clear();  // Make sure the output is empty on error.
+    return false;
+  }
+
+  utf16->resize(actual_size);
+  return true;
+}
+
diff --git a/base/i18n/string_conversions.h b/base/i18n/string_conversions.h
new file mode 100644
index 0000000..c055bb1
--- /dev/null
+++ b/base/i18n/string_conversions.h
@@ -0,0 +1,101 @@
+// Copyright (c) 2009 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_I18N_STRING_CONVERSIONS_H_
+#define BASE_I18N_STRING_CONVERSIONS_H_
+
+#include <string>
+
+#include "base/string16.h"
+#include "base/string_piece.h"
+
+// These convert between UTF-8, -16, and -32 strings. They are potentially slow,
+// so avoid unnecessary conversions. The low-level versions return a boolean
+// indicating whether the conversion was 100% valid. In this case, it will still
+// do the best it can and put the result in the output buffer. The versions that
+// return strings ignore this error and just return the best conversion
+// possible.
+//
+// Note that only the structural validity is checked and non-character
+// codepoints and unassigned are regarded as valid.
+// TODO(jungshik): Consider replacing an invalid input sequence with
+// the Unicode replacement character or adding |replacement_char| parameter.
+// Currently, it's skipped in the ouput, which could be problematic in
+// some situations.
+bool WideToUTF8(const wchar_t* src, size_t src_len, std::string* output);
+std::string WideToUTF8(const std::wstring& wide);
+bool UTF8ToWide(const char* src, size_t src_len, std::wstring* output);
+std::wstring UTF8ToWide(const base::StringPiece& utf8);
+
+bool WideToUTF16(const wchar_t* src, size_t src_len, string16* output);
+string16 WideToUTF16(const std::wstring& wide);
+bool UTF16ToWide(const char16* src, size_t src_len, std::wstring* output);
+std::wstring UTF16ToWide(const string16& utf16);
+
+bool UTF8ToUTF16(const char* src, size_t src_len, string16* output);
+string16 UTF8ToUTF16(const std::string& utf8);
+bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output);
+std::string UTF16ToUTF8(const string16& utf16);
+
+// We are trying to get rid of wstring as much as possible, but it's too big
+// a mess to do it all at once.  These conversions should be used when we
+// really should just be passing a string16 around, but we haven't finished
+// porting whatever module uses wstring and the conversion is being used as a
+// stopcock.  This makes it easy to grep for the ones that should be removed.
+#if defined(OS_WIN)
+# define WideToUTF16Hack
+# define UTF16ToWideHack
+#else
+# define WideToUTF16Hack WideToUTF16
+# define UTF16ToWideHack UTF16ToWide
+#endif
+
+// Defines the error handling modes of UTF16ToCodepage, CodepageToUTF16,
+// WideToCodepage and CodepageToWide.
+class OnStringUtilConversionError {
+ public:
+  enum Type {
+    // The function will return failure. The output buffer will be empty.
+    FAIL,
+
+    // The offending characters are skipped and the conversion will proceed as
+    // if they did not exist.
+    SKIP,
+
+    // When converting to Unicode, the offending byte sequences are substituted
+    // by Unicode replacement character (U+FFFD). When converting from Unicode,
+    // this is the same as SKIP.
+    SUBSTITUTE,
+  };
+
+ private:
+  OnStringUtilConversionError();
+};
+
+// Converts between UTF-16 strings and the encoding specified.  If the
+// encoding doesn't exist or the encoding fails (when on_error is FAIL),
+// returns false.
+bool UTF16ToCodepage(const string16& utf16,
+                     const char* codepage_name,
+                     OnStringUtilConversionError::Type on_error,
+                     std::string* encoded);
+
+bool CodepageToUTF16(const std::string& encoded,
+                     const char* codepage_name,
+                     OnStringUtilConversionError::Type on_error,
+                     string16* utf16);
+
+// Converts between wide strings and the encoding specified.  If the
+// encoding doesn't exist or the encoding fails (when on_error is FAIL),
+// returns false.
+bool WideToCodepage(const std::wstring& wide,
+                    const char* codepage_name,
+                    OnStringUtilConversionError::Type on_error,
+                    std::string* encoded);
+bool CodepageToWide(const std::string& encoded,
+                    const char* codepage_name,
+                    OnStringUtilConversionError::Type on_error,
+                    std::wstring* wide);
+
+#endif  // BASE_I18N_STRING_CONVERSIONS_H_