/* 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/types.h"
#include "../common/port.h"
#include "./fast_log.h"
#include "./prefix.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
static uint32_t kInsBase[] = { 0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26, 34, 50,
66, 98, 130, 194, 322, 578, 1090, 2114, 6210, 22594 };
static uint32_t kInsExtra[] = { 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4,
5, 5, 6, 7, 8, 9, 10, 12, 14, 24 };
static uint32_t kCopyBase[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 18, 22, 30,
38, 54, 70, 102, 134, 198, 326, 582, 1094, 2118 };
static uint32_t kCopyExtra[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3,
4, 4, 5, 5, 6, 7, 8, 9, 10, 24 };
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, int use_last_distance) {
uint16_t bits64 =
(uint16_t)((copycode & 0x7u) | ((inscode & 0x7u) << 3));
if (use_last_distance && inscode < 8 && copycode < 16) {
return (copycode < 8) ? bits64 : (bits64 | 64);
} else {
/* "To convert an insert-and-copy length code to an insert length code and
a copy length code, the following table can be used" */
static const uint16_t cells[9] = { 128u, 192u, 384u, 256u, 320u, 512u,
448u, 576u, 640u };
return cells[(copycode >> 3) + 3 * (inscode >> 3)] | bits64;
}
}
static BROTLI_INLINE void GetLengthCode(size_t insertlen, size_t copylen,
int 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 kInsBase[inscode];
}
static BROTLI_INLINE uint32_t GetInsertExtra(uint16_t inscode) {
return kInsExtra[inscode];
}
static BROTLI_INLINE uint32_t GetCopyBase(uint16_t copycode) {
return kCopyBase[copycode];
}
static BROTLI_INLINE uint32_t GetCopyExtra(uint16_t copycode) {
return kCopyExtra[copycode];
}
typedef struct Command {
uint32_t insert_len_;
/* Stores copy_len in low 24 bits and copy_len XOR copy_code in high 8 bit. */
uint32_t copy_len_;
uint32_t dist_extra_;
uint16_t cmd_prefix_;
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, size_t insertlen,
size_t copylen, size_t copylen_code, size_t distance_code) {
self->insert_len_ = (uint32_t)insertlen;
self->copy_len_ = (uint32_t)(copylen | ((copylen_code ^ copylen) << 24));
/* 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, 0, 0, &self->dist_prefix_, &self->dist_extra_);
GetLengthCode(
insertlen, copylen_code, self->dist_prefix_ == 0, &self->cmd_prefix_);
}
static BROTLI_INLINE void InitInsertCommand(Command* self, size_t insertlen) {
self->insert_len_ = (uint32_t)insertlen;
self->copy_len_ = 4 << 24;
self->dist_extra_ = 0;
self->dist_prefix_ = 16;
GetLengthCode(insertlen, 4, 0, &self->cmd_prefix_);
}
static BROTLI_INLINE uint32_t CommandDistanceCode(const Command* self) {
if (self->dist_prefix_ < 16) {
return self->dist_prefix_;
} else {
uint32_t nbits = self->dist_extra_ >> 24;
uint32_t extra = self->dist_extra_ & 0xffffff;
uint32_t prefix = self->dist_prefix_ - 12u - 2u * nbits;
return (prefix << nbits) + extra + 12;
}
}
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_ & 0xFFFFFF;
}
static BROTLI_INLINE uint32_t CommandCopyLenCode(const Command* self) {
return (self->copy_len_ & 0xFFFFFF) ^ (self->copy_len_ >> 24);
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
#endif /* BROTLI_ENC_COMMAND_H_ */
