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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
*/
/* This class models a sequence of literals and a backward reference copy. */
#ifndef BROTLI_ENC_COMMAND_H_
#define BROTLI_ENC_COMMAND_H_
#include "../common/constants.h"
#include "../common/platform.h"
#include <brotli/types.h>
#include "./fast_log.h"
#include "./params.h"
#include "./prefix.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
BROTLI_INTERNAL extern const uint32_t
kBrotliInsBase[BROTLI_NUM_INS_COPY_CODES];
BROTLI_INTERNAL extern const uint32_t
kBrotliInsExtra[BROTLI_NUM_INS_COPY_CODES];
BROTLI_INTERNAL extern const uint32_t
kBrotliCopyBase[BROTLI_NUM_INS_COPY_CODES];
BROTLI_INTERNAL extern const uint32_t
kBrotliCopyExtra[BROTLI_NUM_INS_COPY_CODES];
static BROTLI_INLINE uint16_t GetInsertLengthCode(size_t insertlen) {
if (insertlen < 6) {
return (uint16_t)insertlen;
} else if (insertlen < 130) {
uint32_t nbits = Log2FloorNonZero(insertlen - 2) - 1u;
return (uint16_t)((nbits << 1) + ((insertlen - 2) >> nbits) + 2);
} else if (insertlen < 2114) {
return (uint16_t)(Log2FloorNonZero(insertlen - 66) + 10);
} else if (insertlen < 6210) {
return 21u;
} else if (insertlen < 22594) {
return 22u;
} else {
return 23u;
}
}
static BROTLI_INLINE uint16_t GetCopyLengthCode(size_t copylen) {
if (copylen < 10) {
return (uint16_t)(copylen - 2);
} else if (copylen < 134) {
uint32_t nbits = Log2FloorNonZero(copylen - 6) - 1u;
return (uint16_t)((nbits << 1) + ((copylen - 6) >> nbits) + 4);
} else if (copylen < 2118) {
return (uint16_t)(Log2FloorNonZero(copylen - 70) + 12);
} else {
return 23u;
}
}
static BROTLI_INLINE uint16_t CombineLengthCodes(
uint16_t inscode, uint16_t copycode, BROTLI_BOOL use_last_distance) {
uint16_t bits64 =
(uint16_t)((copycode & 0x7u) | ((inscode & 0x7u) << 3u));
if (use_last_distance && inscode < 8u && copycode < 16u) {
return (copycode < 8u) ? bits64 : (bits64 | 64u);
} else {
/* Specification: 5 Encoding of ... (last table) */
/* offset = 2 * index, where index is in range [0..8] */
uint32_t offset = 2u * ((copycode >> 3u) + 3u * (inscode >> 3u));
/* All values in specification are K * 64,
where K = [2, 3, 6, 4, 5, 8, 7, 9, 10],
i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9],
K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D.
All values in D require only 2 bits to encode.
Magic constant is shifted 6 bits left, to avoid final multiplication. */
offset = (offset << 5u) + 0x40u + ((0x520D40u >> offset) & 0xC0u);
return (uint16_t)(offset | bits64);
}
}
static BROTLI_INLINE void GetLengthCode(size_t insertlen, size_t copylen,
BROTLI_BOOL use_last_distance,
uint16_t* code) {
uint16_t inscode = GetInsertLengthCode(insertlen);
uint16_t copycode = GetCopyLengthCode(copylen);
*code = CombineLengthCodes(inscode, copycode, use_last_distance);
}
static BROTLI_INLINE uint32_t GetInsertBase(uint16_t inscode) {
return kBrotliInsBase[inscode];
}
static BROTLI_INLINE uint32_t GetInsertExtra(uint16_t inscode) {
return kBrotliInsExtra[inscode];
}
static BROTLI_INLINE uint32_t GetCopyBase(uint16_t copycode) {
return kBrotliCopyBase[copycode];
}
static BROTLI_INLINE uint32_t GetCopyExtra(uint16_t copycode) {
return kBrotliCopyExtra[copycode];
}
typedef struct Command {
uint32_t insert_len_;
/* Stores copy_len in low 25 bits and copy_code - copy_len in high 7 bit. */
uint32_t copy_len_;
/* Stores distance extra bits. */
uint32_t dist_extra_;
uint16_t cmd_prefix_;
/* Stores distance code in low 10 bits
and number of extra bits in high 6 bits. */
uint16_t dist_prefix_;
} Command;
/* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */
static BROTLI_INLINE void InitCommand(Command* self,
const BrotliDistanceParams* dist, size_t insertlen,
size_t copylen, int copylen_code_delta, size_t distance_code) {
/* Don't rely on signed int representation, use honest casts. */
uint32_t delta = (uint8_t)((int8_t)copylen_code_delta);
self->insert_len_ = (uint32_t)insertlen;
self->copy_len_ = (uint32_t)(copylen | (delta << 25));
/* The distance prefix and extra bits are stored in this Command as if
npostfix and ndirect were 0, they are only recomputed later after the
clustering if needed. */
PrefixEncodeCopyDistance(
distance_code, dist->num_direct_distance_codes,
dist->distance_postfix_bits, &self->dist_prefix_, &self->dist_extra_);
GetLengthCode(
insertlen, (size_t)((int)copylen + copylen_code_delta),
TO_BROTLI_BOOL((self->dist_prefix_ & 0x3FF) == 0), &self->cmd_prefix_);
}
static BROTLI_INLINE void InitInsertCommand(Command* self, size_t insertlen) {
self->insert_len_ = (uint32_t)insertlen;
self->copy_len_ = 4 << 25;
self->dist_extra_ = 0;
self->dist_prefix_ = BROTLI_NUM_DISTANCE_SHORT_CODES;
GetLengthCode(insertlen, 4, BROTLI_FALSE, &self->cmd_prefix_);
}
static BROTLI_INLINE uint32_t CommandRestoreDistanceCode(
const Command* self, const BrotliDistanceParams* dist) {
if ((self->dist_prefix_ & 0x3FFu) <
BROTLI_NUM_DISTANCE_SHORT_CODES + dist->num_direct_distance_codes) {
return self->dist_prefix_ & 0x3FFu;
} else {
uint32_t dcode = self->dist_prefix_ & 0x3FFu;
uint32_t nbits = self->dist_prefix_ >> 10;
uint32_t extra = self->dist_extra_;
uint32_t postfix_mask = (1U << dist->distance_postfix_bits) - 1U;
uint32_t hcode = (dcode - dist->num_direct_distance_codes -
BROTLI_NUM_DISTANCE_SHORT_CODES) >>
dist->distance_postfix_bits;
uint32_t lcode = (dcode - dist->num_direct_distance_codes -
BROTLI_NUM_DISTANCE_SHORT_CODES) & postfix_mask;
uint32_t offset = ((2U + (hcode & 1U)) << nbits) - 4U;
return ((offset + extra) << dist->distance_postfix_bits) + lcode +
dist->num_direct_distance_codes + BROTLI_NUM_DISTANCE_SHORT_CODES;
}
}
static BROTLI_INLINE uint32_t CommandDistanceContext(const Command* self) {
uint32_t r = self->cmd_prefix_ >> 6;
uint32_t c = self->cmd_prefix_ & 7;
if ((r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2)) {
return c;
}
return 3;
}
static BROTLI_INLINE uint32_t CommandCopyLen(const Command* self) {
return self->copy_len_ & 0x1FFFFFF;
}
static BROTLI_INLINE uint32_t CommandCopyLenCode(const Command* self) {
uint32_t modifier = self->copy_len_ >> 25;
int32_t delta = (int8_t)((uint8_t)(modifier | ((modifier & 0x40) << 1)));
return (uint32_t)((int32_t)(self->copy_len_ & 0x1FFFFFF) + delta);
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
#endif /* BROTLI_ENC_COMMAND_H_ */
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