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46 lines
1.8 KiB
46 lines
1.8 KiB
/* Copyright 2021 QMK
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "utf8.h"
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// Borrowed from https://nullprogram.com/blog/2017/10/06/
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const char *decode_utf8(const char *str, int32_t *code_point) {
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const char *next;
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if (str[0] < 0x80) { // U+0000-007F
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*code_point = str[0];
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next = str + 1;
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} else if ((str[0] & 0xE0) == 0xC0) { // U+0080-07FF
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*code_point = ((int32_t)(str[0] & 0x1F) << 6) | ((int32_t)(str[1] & 0x3F) << 0);
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next = str + 2;
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} else if ((str[0] & 0xF0) == 0xE0) { // U+0800-FFFF
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*code_point = ((int32_t)(str[0] & 0x0F) << 12) | ((int32_t)(str[1] & 0x3F) << 6) | ((int32_t)(str[2] & 0x3F) << 0);
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next = str + 3;
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} else if ((str[0] & 0xF8) == 0xF0 && (str[0] <= 0xF4)) { // U+10000-10FFFF
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*code_point = ((int32_t)(str[0] & 0x07) << 18) | ((int32_t)(str[1] & 0x3F) << 12) | ((int32_t)(str[2] & 0x3F) << 6) | ((int32_t)(str[3] & 0x3F) << 0);
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next = str + 4;
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} else {
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*code_point = -1;
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next = str + 1;
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}
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// part of a UTF-16 surrogate pair - invalid
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if (*code_point >= 0xD800 && *code_point <= 0xDFFF) {
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*code_point = -1;
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}
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return next;
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}
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