/* 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/port.h" | |
#include "../common/types.h" | |
#include "./fast_log.h" | |
#if defined(__cplusplus) || defined(c_plusplus) | |
extern "C" { | |
#endif | |
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)( | |
(BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_codes + | |
((2 * (nbits - 1) + prefix) << postfix_bits) + postfix)); | |
*extra_bits = (uint32_t)( | |
(nbits << 24) | ((dist - offset) >> postfix_bits)); | |
} | |
} | |
#if defined(__cplusplus) || defined(c_plusplus) | |
} /* extern "C" */ | |
#endif | |
#endif /* BROTLI_ENC_PREFIX_H_ */ |