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/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
file Copyright.txt or https://cmake.org/licensing for details. */
#include "cm_utf8.h"
/*
RFC 3629
07-bit: 0xxxxxxx
11-bit: 110xxxxx 10xxxxxx
16-bit: 1110xxxx 10xxxxxx 10xxxxxx
21-bit: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
Pre-RFC Compatibility
26-bit: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
31-bit: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
*/
/* Number of leading ones before a zero in the byte. */
unsigned char const cm_utf8_ones[256] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 7, 8
};
/* Mask away control bits from bytes with n leading ones. */
static unsigned char const cm_utf8_mask[7] = { 0xEF, 0x3F, 0x1F, 0x0F,
0x07, 0x03, 0x01 };
/* Minimum allowed value when first byte has n leading ones. */
static unsigned int const cm_utf8_min[7] = {
0, 0, 1u << 7, 1u << 11, 1u << 16, 1u << 21, 1u << 26 /*, 1u<<31 */
};
const char* cm_utf8_decode_character(const char* first, const char* last,
unsigned int* pc)
{
/* Count leading ones in the first byte. */
unsigned char c = (unsigned char)*first++;
unsigned char const ones = cm_utf8_ones[c];
switch (ones) {
case 0:
*pc = c;
return first; /* One-byte character. */
case 1:
case 7:
case 8:
return 0; /* Invalid leading byte. */
default:
break;
}
/* Extract bits from this multi-byte character. */
{
unsigned int uc = c & cm_utf8_mask[ones];
int left;
for (left = ones - 1; left && first != last; --left) {
c = (unsigned char)*first++;
if (cm_utf8_ones[c] != 1) {
return 0;
}
uc = (uc << 6) | (c & cm_utf8_mask[1]);
}
if (left > 0 || uc < cm_utf8_min[ones]) {
return 0;
}
/* UTF-16 surrogate halves. */
if (0xD800 <= uc && uc <= 0xDFFF) {
return 0;
}
*pc = uc;
return first;
}
}
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