| /* 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 "./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, BROTLI_BOOL 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 { |
| /* Specification: 5 Encoding of ... (last table) */ |
| /* offset = 2 * index, where index is in range [0..8] */ |
| int offset = 2 * ((copycode >> 3) + 3 * (inscode >> 3)); |
| /* 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 << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0); |
| 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 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, 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 << 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, (size_t)((int)copylen + copylen_code_delta), |
| TO_BROTLI_BOOL(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_ = BROTLI_NUM_DISTANCE_SHORT_CODES; |
| GetLengthCode(insertlen, 4, BROTLI_FALSE, &self->cmd_prefix_); |
| } |
| |
| static BROTLI_INLINE uint32_t CommandRestoreDistanceCode(const Command* self) { |
| if (self->dist_prefix_ < BROTLI_NUM_DISTANCE_SHORT_CODES) { |
| return self->dist_prefix_; |
| } else { |
| uint32_t nbits = self->dist_extra_ >> 24; |
| uint32_t extra = self->dist_extra_ & 0xffffff; |
| /* It is assumed that the distance was first encoded with NPOSTFIX = 0 and |
| NDIRECT = 0, so the code itself is of this form: |
| BROTLI_NUM_DISTANCE_SHORT_CODES + 2 * (nbits - 1) + prefix_bit |
| Therefore, the following expression results in (2 + prefix_bit). */ |
| uint32_t prefix = |
| self->dist_prefix_ + 4u - BROTLI_NUM_DISTANCE_SHORT_CODES - 2u * nbits; |
| /* Subtract 4 for offset (Chapter 4.) and |
| increase by BROTLI_NUM_DISTANCE_SHORT_CODES - 1 */ |
| return (prefix << nbits) + extra + BROTLI_NUM_DISTANCE_SHORT_CODES - 4u; |
| } |
| } |
| |
| 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) { |
| int32_t delta = (int8_t)((uint8_t)(self->copy_len_ >> 24)); |
| return (uint32_t)((int32_t)(self->copy_len_ & 0xFFFFFF) + delta); |
| } |
| |
| #if defined(__cplusplus) || defined(c_plusplus) |
| } /* extern "C" */ |
| #endif |
| |
| #endif /* BROTLI_ENC_COMMAND_H_ */ |