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/* See LICENSE file for copyright and license details. */
#include "libsimple.h"
int
libsimple_isutf8(const char *string, int allow_modified_nul)
{
static long BYTES_TO_MIN_BITS[] = {0, 0, 8, 12, 17, 22, 37};
static long BYTES_TO_MAX_BITS[] = {0, 7, 11, 16, 21, 26, 31};
long int bytes = 0, read_bytes = 0, bits = 0, c, character;
/* min bits max bits
0....... 0 7
110..... 10...... 8 11
1110.... 10...... 10...... 12 16
11110... 10...... 10...... 10...... 17 21
111110.. 10...... 10...... 10...... 10...... 22 26
1111110. 10...... 10...... 10...... 10...... 10...... 27 31
*/
while ((c = (long int)(*string++))) {
if (!read_bytes) {
/* First byte of the character. */
if (!(c & 0x80))
/* Single-byte character. */
continue;
if ((c & 0xC0) == 0x80)
/* Single-byte character marked as multibyte, or
a non-first byte in a multibyte character. */
return 0;
/* Multibyte character. */
while ((c & 0x80))
bytes++, c <<= 1;
read_bytes = 1;
character = c & 0x7F;
if (bytes > 6)
/* 31-bit characters can be encoded with 6-bytes,
and UTF-8 does not cover higher code points. */
return 0;
} else {
/* Not first byte of the character. */
if ((c & 0xC0) != 0x80)
/* Beginning of new character before a
multibyte character has ended. */
return 0;
character = (character << 6) | (c & 0x7F);
if (++read_bytes < bytes)
/* Not at last byte yet. */
continue;
/* Check that the character is not unnecessarily long. */
while (character)
character >>= 1, bits++;
bits = (!bits && bytes == 2 && allow_modified_nul) ? 8 : bits;
if (bits < BYTES_TO_MIN_BITS[bytes] || BYTES_TO_MAX_BITS[bytes] < bits)
return 0;
read_bytes = bytes = bits = 0;
}
}
/* Make sure we did not stop at the middle of a multibyte character. */
return !read_bytes;
}
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