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Diffstat (limited to 'modules/brotli/enc/command.h')
| -rw-r--r-- | modules/brotli/enc/command.h | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/modules/brotli/enc/command.h b/modules/brotli/enc/command.h new file mode 100644 index 000000000..1aac85689 --- /dev/null +++ b/modules/brotli/enc/command.h @@ -0,0 +1,190 @@ +/* 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 + +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) << 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 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 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_ */ |