| /* 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)( |
| (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_ */ |
