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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
*/
/* Functions for encoding of integers into prefix codes the amount of extra
bits, and the actual values of the extra bits. */
#ifndef BROTLI_ENC_PREFIX_H_
#define BROTLI_ENC_PREFIX_H_
#include "../common/constants.h"
#include "../common/platform.h"
#include <brotli/types.h>
#include "./fast_log.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
/* Here distance_code is an intermediate code, i.e. one of the special codes or
the actual distance increased by BROTLI_NUM_DISTANCE_SHORT_CODES - 1. */
static BROTLI_INLINE void PrefixEncodeCopyDistance(size_t distance_code,
size_t num_direct_codes,
size_t postfix_bits,
uint16_t* code,
uint32_t* extra_bits) {
if (distance_code < BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_codes) {
*code = (uint16_t)distance_code;
*extra_bits = 0;
return;
} else {
size_t dist = ((size_t)1 << (postfix_bits + 2u)) +
(distance_code - BROTLI_NUM_DISTANCE_SHORT_CODES - num_direct_codes);
size_t bucket = Log2FloorNonZero(dist) - 1;
size_t postfix_mask = (1u << postfix_bits) - 1;
size_t postfix = dist & postfix_mask;
size_t prefix = (dist >> bucket) & 1;
size_t offset = (2 + prefix) << bucket;
size_t nbits = bucket - postfix_bits;
*code = (uint16_t)((nbits << 10) |
(BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_codes +
((2 * (nbits - 1) + prefix) << postfix_bits) + postfix));
*extra_bits = (uint32_t)((dist - offset) >> postfix_bits);
}
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
#endif /* BROTLI_ENC_PREFIX_H_ */
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