1 // Copyright 2011 The Chromium Authors 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 <string> 9 #include <string_view> 10 11 #include "base/i18n/base_i18n_export.h" 12 13 namespace base { 14 namespace i18n { 15 16 // UNICODE CASE-HANDLING ADVICE 17 // 18 // In English it's always safe to convert to upper-case or lower-case text 19 // and get a good answer. But some languages have rules specific to those 20 // locales. One example is the Turkish I: 21 // http://www.i18nguy.com/unicode/turkish-i18n.html 22 // 23 // ToLower/ToUpper use the current ICU locale which will take into account 24 // the user language preference. Use this when dealing with user typing. 25 // 26 // FoldCase canonicalizes to a standardized form independent of the current 27 // locale. Use this when comparing general Unicode strings that don't 28 // necessarily belong in the user's current locale (like commands, protocol 29 // names, other strings from the web) for case-insensitive equality. 30 // 31 // Note that case conversions will change the length of the string in some 32 // not-uncommon cases. Never assume that the output is the same length as 33 // the input. 34 35 // Returns the lower case equivalent of string. Uses ICU's current locale. 36 BASE_I18N_EXPORT std::u16string ToLower(std::u16string_view string); 37 38 // Returns the upper case equivalent of string. Uses ICU's current locale. 39 BASE_I18N_EXPORT std::u16string ToUpper(std::u16string_view string); 40 41 // Convert the given string to a canonical case, independent of the current 42 // locale. For ASCII the canonical form is lower case. 43 // See http://unicode.org/faq/casemap_charprop.html#2 44 BASE_I18N_EXPORT std::u16string FoldCase(std::u16string_view string); 45 46 } // namespace i18n 47 } // namespace base 48 49 #endif // BASE_I18N_CASE_CONVERSION_H_ 50