// // Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019 // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #pragma once #include "td/utils/common.h" #include "td/utils/Slice.h" namespace td { /// checks UTF-8 string for correctness bool check_utf8(CSlice str); /// checks if a code unit is a first code unit of a UTF-8 character inline bool is_utf8_character_first_code_unit(unsigned char c) { return (c & 0xC0) != 0x80; } /// returns length of UTF-8 string in characters inline size_t utf8_length(Slice str) { size_t result = 0; for (auto c : str) { result += is_utf8_character_first_code_unit(c); } return result; } /// appends a Unicode character using UTF-8 encoding void append_utf8_character(string &str, uint32 ch); /// moves pointer one UTF-8 character back inline const unsigned char *prev_utf8_unsafe(const unsigned char *ptr) { while (!is_utf8_character_first_code_unit(*--ptr)) { // pass } return ptr; } /// moves pointer one UTF-8 character forward and saves code of the skipped character in *code const unsigned char *next_utf8_unsafe(const unsigned char *ptr, uint32 *code, const char *source); /// truncates UTF-8 string to the given length in Unicode characters template <class T> T utf8_truncate(T str, size_t length) { if (str.size() > length) { for (size_t i = 0; i < str.size(); i++) { if (is_utf8_character_first_code_unit(static_cast<unsigned char>(str[i]))) { if (length == 0) { return str.substr(0, i); } else { length--; } } } } return str; } /// truncates UTF-8 string to the given length given in UTF-16 code units template <class T> T utf8_utf16_truncate(T str, size_t length) { for (size_t i = 0; i < str.size(); i++) { auto c = static_cast<unsigned char>(str[i]); if (is_utf8_character_first_code_unit(c)) { if (length <= 0) { return str.substr(0, i); } else { length--; if (c >= 0xf0) { // >= 4 bytes in symbol => surrogaite pair length--; } } } } return str; } template <class T> T utf8_substr(T str, size_t offset) { auto offset_pos = utf8_truncate(str, offset).size(); return str.substr(offset_pos); } template <class T> T utf8_substr(T str, size_t offset, size_t length) { return utf8_truncate(utf8_substr(str, offset), length); } template <class T> T utf8_utf16_substr(T str, size_t offset) { auto offset_pos = utf8_utf16_truncate(str, offset).size(); return str.substr(offset_pos); } template <class T> T utf8_utf16_substr(T str, size_t offset, size_t length) { return utf8_utf16_truncate(utf8_utf16_substr(str, offset), length); } /// Returns UTF-8 string converted to lower case. string utf8_to_lower(Slice str); } // namespace td