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