181 lines
6.5 KiB
C
181 lines
6.5 KiB
C
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/* Copyright 2013 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* This class models a sequence of literals and a backward reference copy. */
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#ifndef BROTLI_ENC_COMMAND_H_
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#define BROTLI_ENC_COMMAND_H_
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#include "../common/constants.h"
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#include <brotli/port.h>
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#include <brotli/types.h>
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#include "./fast_log.h"
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#include "./prefix.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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static uint32_t kInsBase[] = { 0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26, 34, 50,
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66, 98, 130, 194, 322, 578, 1090, 2114, 6210, 22594 };
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static uint32_t kInsExtra[] = { 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4,
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5, 5, 6, 7, 8, 9, 10, 12, 14, 24 };
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static uint32_t kCopyBase[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 18, 22, 30,
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38, 54, 70, 102, 134, 198, 326, 582, 1094, 2118 };
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static uint32_t kCopyExtra[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3,
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4, 4, 5, 5, 6, 7, 8, 9, 10, 24 };
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static BROTLI_INLINE uint16_t GetInsertLengthCode(size_t insertlen) {
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if (insertlen < 6) {
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return (uint16_t)insertlen;
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} else if (insertlen < 130) {
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uint32_t nbits = Log2FloorNonZero(insertlen - 2) - 1u;
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return (uint16_t)((nbits << 1) + ((insertlen - 2) >> nbits) + 2);
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} else if (insertlen < 2114) {
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return (uint16_t)(Log2FloorNonZero(insertlen - 66) + 10);
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} else if (insertlen < 6210) {
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return 21u;
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} else if (insertlen < 22594) {
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return 22u;
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} else {
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return 23u;
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}
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}
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static BROTLI_INLINE uint16_t GetCopyLengthCode(size_t copylen) {
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if (copylen < 10) {
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return (uint16_t)(copylen - 2);
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} else if (copylen < 134) {
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uint32_t nbits = Log2FloorNonZero(copylen - 6) - 1u;
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return (uint16_t)((nbits << 1) + ((copylen - 6) >> nbits) + 4);
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} else if (copylen < 2118) {
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return (uint16_t)(Log2FloorNonZero(copylen - 70) + 12);
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} else {
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return 23u;
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}
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}
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static BROTLI_INLINE uint16_t CombineLengthCodes(
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uint16_t inscode, uint16_t copycode, BROTLI_BOOL use_last_distance) {
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uint16_t bits64 =
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(uint16_t)((copycode & 0x7u) | ((inscode & 0x7u) << 3));
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if (use_last_distance && inscode < 8 && copycode < 16) {
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return (copycode < 8) ? bits64 : (bits64 | 64);
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} else {
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/* Specification: 5 Encoding of ... (last table) */
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/* offset = 2 * index, where index is in range [0..8] */
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int offset = 2 * ((copycode >> 3) + 3 * (inscode >> 3));
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/* All values in specification are K * 64,
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where K = [2, 3, 6, 4, 5, 8, 7, 9, 10],
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i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9],
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K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D.
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All values in D require only 2 bits to encode.
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Magic constant is shifted 6 bits left, to avoid final multiplication. */
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offset = (offset << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0);
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return (uint16_t)offset | bits64;
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}
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}
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static BROTLI_INLINE void GetLengthCode(size_t insertlen, size_t copylen,
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BROTLI_BOOL use_last_distance,
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uint16_t* code) {
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uint16_t inscode = GetInsertLengthCode(insertlen);
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uint16_t copycode = GetCopyLengthCode(copylen);
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*code = CombineLengthCodes(inscode, copycode, use_last_distance);
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}
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static BROTLI_INLINE uint32_t GetInsertBase(uint16_t inscode) {
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return kInsBase[inscode];
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}
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static BROTLI_INLINE uint32_t GetInsertExtra(uint16_t inscode) {
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return kInsExtra[inscode];
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}
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static BROTLI_INLINE uint32_t GetCopyBase(uint16_t copycode) {
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return kCopyBase[copycode];
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}
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static BROTLI_INLINE uint32_t GetCopyExtra(uint16_t copycode) {
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return kCopyExtra[copycode];
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}
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typedef struct Command {
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uint32_t insert_len_;
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/* Stores copy_len in low 24 bits and copy_len XOR copy_code in high 8 bit. */
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uint32_t copy_len_;
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uint32_t dist_extra_;
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uint16_t cmd_prefix_;
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uint16_t dist_prefix_;
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} Command;
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/* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */
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static BROTLI_INLINE void InitCommand(Command* self, size_t insertlen,
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size_t copylen, int copylen_code_delta, size_t distance_code) {
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/* Don't rely on signed int representation, use honest casts. */
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uint32_t delta = (uint8_t)((int8_t)copylen_code_delta);
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self->insert_len_ = (uint32_t)insertlen;
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self->copy_len_ = (uint32_t)(copylen | (delta << 24));
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/* The distance prefix and extra bits are stored in this Command as if
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npostfix and ndirect were 0, they are only recomputed later after the
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clustering if needed. */
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PrefixEncodeCopyDistance(
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distance_code, 0, 0, &self->dist_prefix_, &self->dist_extra_);
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GetLengthCode(
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insertlen, (size_t)((int)copylen + copylen_code_delta),
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TO_BROTLI_BOOL(self->dist_prefix_ == 0), &self->cmd_prefix_);
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}
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static BROTLI_INLINE void InitInsertCommand(Command* self, size_t insertlen) {
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self->insert_len_ = (uint32_t)insertlen;
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self->copy_len_ = 4 << 24;
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self->dist_extra_ = 0;
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self->dist_prefix_ = BROTLI_NUM_DISTANCE_SHORT_CODES;
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GetLengthCode(insertlen, 4, BROTLI_FALSE, &self->cmd_prefix_);
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}
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static BROTLI_INLINE uint32_t CommandRestoreDistanceCode(const Command* self) {
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if (self->dist_prefix_ < BROTLI_NUM_DISTANCE_SHORT_CODES) {
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return self->dist_prefix_;
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} else {
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uint32_t nbits = self->dist_extra_ >> 24;
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uint32_t extra = self->dist_extra_ & 0xffffff;
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/* It is assumed that the distance was first encoded with NPOSTFIX = 0 and
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NDIRECT = 0, so the code itself is of this form:
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BROTLI_NUM_DISTANCE_SHORT_CODES + 2 * (nbits - 1) + prefix_bit
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Therefore, the following expression results in (2 + prefix_bit). */
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uint32_t prefix =
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self->dist_prefix_ + 4u - BROTLI_NUM_DISTANCE_SHORT_CODES - 2u * nbits;
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/* Subtract 4 for offset (Chapter 4.) and
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increase by BROTLI_NUM_DISTANCE_SHORT_CODES - 1 */
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return (prefix << nbits) + extra + BROTLI_NUM_DISTANCE_SHORT_CODES - 4u;
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}
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}
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static BROTLI_INLINE uint32_t CommandDistanceContext(const Command* self) {
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uint32_t r = self->cmd_prefix_ >> 6;
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uint32_t c = self->cmd_prefix_ & 7;
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if ((r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2)) {
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return c;
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}
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return 3;
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}
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static BROTLI_INLINE uint32_t CommandCopyLen(const Command* self) {
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return self->copy_len_ & 0xFFFFFF;
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}
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static BROTLI_INLINE uint32_t CommandCopyLenCode(const Command* self) {
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int32_t delta = (int8_t)((uint8_t)(self->copy_len_ >> 24));
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return (uint32_t)((int32_t)(self->copy_len_ & 0xFFFFFF) + delta);
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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} /* extern "C" */
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#endif
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#endif /* BROTLI_ENC_COMMAND_H_ */
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