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