base/i18n/case_conversion.h

   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_I18N_CASE_CONVERSION_H_
   6 #define BASE_I18N_CASE_CONVERSION_H_
   7
   8 #include "base/i18n/base_i18n_export.h"
   9 #include "base/strings/string16.h"
  10 #include "base/strings/string_piece.h"
  11
  12 namespace base {
  13 namespace i18n {
  14
  15 // UNICODE CASE-HANDLING ADVICE
  16 //
  17 // In English it's always safe to convert to upper-case or lower-case text
  18 // and get a good answer. But some languages have rules specific to those
  19 // locales. One example is the Turkish I:
  20 //   http://www.i18nguy.com/unicode/turkish-i18n.html
  21 //
  22 // ToLower/ToUpper use the current ICU locale which will take into account
  23 // the user language preference. Use this when dealing with user typing.
  24 //
  25 // FoldCase canonicalizes to a standardized form independent of the current
  26 // locale. Use this when comparing general Unicode strings that don't
  27 // necessarily belong in the user's current locale (like commands, protocol
  28 // names, other strings from the web) for case-insensitive equality.
  29 //
  30 // Note that case conversions will change the length of the string in some
  31 // not-uncommon cases. Never assume that the output is the same length as
  32 // the input.
  33
  34 // Returns the lower case equivalent of string. Uses ICU's current locale.
  35 BASE_I18N_EXPORT string16 ToLower(StringPiece16 string);
  36
  37 // Returns the upper case equivalent of string. Uses ICU's current locale.
  38 BASE_I18N_EXPORT string16 ToUpper(StringPiece16 string);
  39
  40 // Convert the given string to a canonical case, independent of the current
  41 // locale. For ASCII the canonical form is lower case.
  42 // See http://unicode.org/faq/casemap_charprop.html#2
  43 BASE_I18N_EXPORT string16 FoldCase(StringPiece16 string);
  44
  45 }  // namespace i18n
  46 }  // namespace base
  47
  48 #endif  // BASE_I18N_CASE_CONVERSION_H_