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/* libmisc/utf8.c - UTF-8 routines
*
* Copyright (C) 2024-2025 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#include <libmisc/utf8.h>
void utf8_decode_codepoint(const uint8_t *str, size_t len, uint32_t *ret_ch, uint8_t *ret_chlen) {
uint32_t ch;
uint8_t chlen;
uint32_t chmin;
if ((str[0] & 0b10000000) == 0b00000000) { ch = str[0] & 0b01111111; chlen = 1; chmin = 0; } /* bits=7+(0*6)= 7 */
else if ((str[0] & 0b11100000) == 0b11000000) { ch = str[0] & 0b00011111; chlen = 2; chmin = UINT32_C(1)<< 7; } /* bits=5+(1*6)=11 */
else if ((str[0] & 0b11110000) == 0b11100000) { ch = str[0] & 0b00001111; chlen = 3; chmin = UINT32_C(1)<<11; } /* bits=4+(2*6)=16 */
else if ((str[0] & 0b11111000) == 0b11110000) { ch = str[0] & 0b00000111; chlen = 4; chmin = UINT32_C(1)<<16; } /* bits=3+(3*6)=21 */
else goto invalid;
if (chlen > len)
goto invalid;
for (uint8_t i = 1; i < chlen; i++) {
if ((str[i] & 0b11000000) != 0b10000000)
goto invalid;
ch = (ch << 6) | (str[i] & 0b00111111);
}
if (ch > 0x10FFFF || ch < chmin)
goto invalid;
*ret_ch = ch;
*ret_chlen = chlen;
return;
invalid:
*ret_chlen = 0;
}
bool _utf8_is_valid(const uint8_t *str, size_t len, bool forbid_nul) {
for (size_t pos = 0; pos < len;) {
uint32_t ch;
uint8_t chlen;
utf8_decode_codepoint(&str[pos], len-pos, &ch, &chlen);
if (chlen == 0 || (forbid_nul && ch == 0))
return false;
pos += chlen;
}
return true;
}
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