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/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Heuristics for deciding about the UTF8-ness of strings. */
#include "./utf8_util.h"
#include <brotli/types.h>
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
static size_t BrotliParseAsUTF8(
int* symbol, const uint8_t* input, size_t size) {
/* ASCII */
if ((input[0] & 0x80) == 0) {
*symbol = input[0];
if (*symbol > 0) {
return 1;
}
}
/* 2-byte UTF8 */
if (size > 1u &&
(input[0] & 0xE0) == 0xC0 &&
(input[1] & 0xC0) == 0x80) {
*symbol = (((input[0] & 0x1F) << 6) |
(input[1] & 0x3F));
if (*symbol > 0x7F) {
return 2;
}
}
/* 3-byte UFT8 */
if (size > 2u &&
(input[0] & 0xF0) == 0xE0 &&
(input[1] & 0xC0) == 0x80 &&
(input[2] & 0xC0) == 0x80) {
*symbol = (((input[0] & 0x0F) << 12) |
((input[1] & 0x3F) << 6) |
(input[2] & 0x3F));
if (*symbol > 0x7FF) {
return 3;
}
}
/* 4-byte UFT8 */
if (size > 3u &&
(input[0] & 0xF8) == 0xF0 &&
(input[1] & 0xC0) == 0x80 &&
(input[2] & 0xC0) == 0x80 &&
(input[3] & 0xC0) == 0x80) {
*symbol = (((input[0] & 0x07) << 18) |
((input[1] & 0x3F) << 12) |
((input[2] & 0x3F) << 6) |
(input[3] & 0x3F));
if (*symbol > 0xFFFF && *symbol <= 0x10FFFF) {
return 4;
}
}
/* Not UTF8, emit a special symbol above the UTF8-code space */
*symbol = 0x110000 | input[0];
return 1;
}
/* Returns 1 if at least min_fraction of the data is UTF8-encoded.*/
BROTLI_BOOL BrotliIsMostlyUTF8(
const uint8_t* data, const size_t pos, const size_t mask,
const size_t length, const double min_fraction) {
size_t size_utf8 = 0;
size_t i = 0;
while (i < length) {
int symbol;
size_t bytes_read =
BrotliParseAsUTF8(&symbol, &data[(pos + i) & mask], length - i);
i += bytes_read;
if (symbol < 0x110000) size_utf8 += bytes_read;
}
return TO_BROTLI_BOOL(size_utf8 > min_fraction * (double)length);
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
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