107 lines
2.8 KiB
C++
107 lines
2.8 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2018
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include "td/utils/int_types.h"
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#include "td/utils/Slice.h"
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namespace td {
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/// checks UTF-8 string for correctness
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bool check_utf8(CSlice str);
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/// checks if a code unit is a first code unit of a UTF-8 character
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inline bool is_utf8_character_first_code_unit(unsigned char c) {
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return (c & 0xC0) != 0x80;
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}
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/// returns length of UTF-8 string in characters
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inline size_t utf8_length(Slice str) {
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size_t result = 0;
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for (auto c : str) {
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result += is_utf8_character_first_code_unit(c);
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}
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return result;
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}
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/// appends a Unicode character using UTF-8 encoding
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void append_utf8_character(string &str, uint32 ch);
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/// moves pointer one UTF-8 character back
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inline const unsigned char *prev_utf8_unsafe(const unsigned char *ptr) {
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while (!is_utf8_character_first_code_unit(*--ptr)) {
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// pass
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}
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return ptr;
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}
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/// moves pointer one UTF-8 character forward and saves code of the skipped character in *code
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const unsigned char *next_utf8_unsafe(const unsigned char *ptr, uint32 *code);
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/// truncates UTF-8 string to the given length in Unicode characters
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template <class T>
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T utf8_truncate(T str, size_t length) {
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if (str.size() > length) {
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for (size_t i = 0; i < str.size(); i++) {
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if (is_utf8_character_first_code_unit(static_cast<unsigned char>(str[i]))) {
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if (length == 0) {
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return str.substr(0, i);
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} else {
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length--;
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}
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}
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}
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}
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return str;
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}
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/// truncates UTF-8 string to the given length given in UTF-16 code units
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template <class T>
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T utf8_utf16_truncate(T str, size_t length) {
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for (size_t i = 0; i < str.size(); i++) {
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auto c = static_cast<unsigned char>(str[i]);
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if (is_utf8_character_first_code_unit(c)) {
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if (length <= 0) {
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return str.substr(0, i);
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} else {
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length--;
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if (c >= 0xf0) { // >= 4 bytes in symbol => surrogaite pair
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length--;
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}
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}
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}
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}
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return str;
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}
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template <class T>
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T utf8_substr(T str, size_t offset) {
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auto offset_pos = utf8_truncate(str, offset).size();
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return str.substr(offset_pos);
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}
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template <class T>
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T utf8_substr(T str, size_t offset, size_t length) {
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return utf8_truncate(utf8_substr(str, offset), length);
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}
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template <class T>
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T utf8_utf16_substr(T str, size_t offset) {
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auto offset_pos = utf8_utf16_truncate(str, offset).size();
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return str.substr(offset_pos);
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}
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template <class T>
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T utf8_utf16_substr(T str, size_t offset, size_t length) {
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return utf8_utf16_truncate(utf8_utf16_substr(str, offset), length);
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}
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/// Returns UTF-8 string converted to lower case.
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string utf8_to_lower(Slice str);
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} // namespace td
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