diff options
Diffstat (limited to 'quantum/utf8.c')
| -rw-r--r-- | quantum/utf8.c | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/quantum/utf8.c b/quantum/utf8.c new file mode 100644 index 0000000000..4b2cd4d8d4 --- /dev/null +++ b/quantum/utf8.c @@ -0,0 +1,46 @@ +/* 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; +} |