// Copyright 2013 Google Inc. All Rights Reserved. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. // // This class models a sequence of literals and a backward reference copy. #ifndef BROTLI_ENC_COMMAND_H_ #define BROTLI_ENC_COMMAND_H_ #include #include "./fast_log.h" namespace brotli { static inline void GetDistCode(int distance_code, uint16_t* code, uint32_t* extra) { distance_code -= 1; if (distance_code < 16) { *code = distance_code; *extra = 0; } else { distance_code -= 12; int numextra = Log2FloorNonZero(distance_code) - 1; int prefix = distance_code >> numextra; *code = 12 + 2 * numextra + prefix; *extra = (numextra << 24) | (distance_code - (prefix << numextra)); } } static int insbase[] = { 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 int insextra[] = { 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 int copybase[] = { 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 int copyextra[] = { 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 inline int GetInsertLengthCode(int insertlen) { if (insertlen < 6) { return insertlen; } else if (insertlen < 130) { insertlen -= 2; int nbits = Log2FloorNonZero(insertlen) - 1; return (nbits << 1) + (insertlen >> nbits) + 2; } else if (insertlen < 2114) { return Log2FloorNonZero(insertlen - 66) + 10; } else if (insertlen < 6210) { return 21; } else if (insertlen < 22594) { return 22; } else { return 23; } } static inline int GetCopyLengthCode(int copylen) { if (copylen < 10) { return copylen - 2; } else if (copylen < 134) { copylen -= 6; int nbits = Log2FloorNonZero(copylen) - 1; return (nbits << 1) + (copylen >> nbits) + 4; } else if (copylen < 2118) { return Log2FloorNonZero(copylen - 70) + 12; } else { return 23; } } static inline int CombineLengthCodes( int inscode, int copycode, int distancecode) { int bits64 = (copycode & 0x7u) | ((inscode & 0x7u) << 3); if (distancecode == 0 && 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 int cells[9] = { 2, 3, 6, 4, 5, 8, 7, 9, 10 }; return (cells[(copycode >> 3) + 3 * (inscode >> 3)] << 6) | bits64; } } static inline void GetLengthCode(int insertlen, int copylen, int distancecode, uint16_t* code, uint64_t* extra) { int inscode = GetInsertLengthCode(insertlen); int copycode = GetCopyLengthCode(copylen); uint64_t insnumextra = insextra[inscode]; uint64_t numextra = insnumextra + copyextra[copycode]; uint64_t insextraval = insertlen - insbase[inscode]; uint64_t copyextraval = copylen - copybase[copycode]; *code = CombineLengthCodes(inscode, copycode, distancecode); *extra = (numextra << 48) | (copyextraval << insnumextra) | insextraval; } struct Command { Command() {} Command(int insertlen, int copylen, int copylen_code, int distance_code) : insert_len_(insertlen), copy_len_(copylen) { GetDistCode(distance_code, &dist_prefix_, &dist_extra_); GetLengthCode(insertlen, copylen_code, dist_prefix_, &cmd_prefix_, &cmd_extra_); } Command(int insertlen) : insert_len_(insertlen), copy_len_(0), dist_prefix_(16), dist_extra_(0) { GetLengthCode(insertlen, 4, dist_prefix_, &cmd_prefix_, &cmd_extra_); } int DistanceCode() const { if (dist_prefix_ < 16) { return dist_prefix_ + 1; } int nbits = dist_extra_ >> 24; int extra = dist_extra_ & 0xffffff; int prefix = dist_prefix_ - 12 - 2 * nbits; return (prefix << nbits) + extra + 13; } int DistanceContext() const { int r = cmd_prefix_ >> 6; int c = cmd_prefix_ & 7; if ((r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2)) { return c; } return 3; } int insert_len_; int copy_len_; uint16_t cmd_prefix_; uint16_t dist_prefix_; uint64_t cmd_extra_; uint32_t dist_extra_; }; } // namespace brotli #endif // BROTLI_ENC_COMMAND_H_