1 // Copyright 2016 The Draco Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // File provides basic classes and functions for rANS coding. 16 #ifndef DRACO_COMPRESSION_BIT_CODERS_RANS_BIT_ENCODER_H_ 17 #define DRACO_COMPRESSION_BIT_CODERS_RANS_BIT_ENCODER_H_ 18 19 #include <vector> 20 21 #include "draco/core/encoder_buffer.h" 22 23 namespace draco { 24 25 // Class for encoding a sequence of bits using rANS. The probability table used 26 // to encode the bits is based off the total counts of bits. 27 // TODO(fgalligan): Investigate using an adaptive table for more compression. 28 class RAnsBitEncoder { 29 public: 30 RAnsBitEncoder(); 31 ~RAnsBitEncoder(); 32 33 // Must be called before any Encode* function is called. 34 void StartEncoding(); 35 36 // Encode one bit. If |bit| is true encode a 1, otherwise encode a 0. 37 void EncodeBit(bool bit); 38 39 // Encode |nbits| of |value|, starting from the least significant bit. 40 // |nbits| must be > 0 and <= 32. 41 void EncodeLeastSignificantBits32(int nbits, uint32_t value); 42 43 // Ends the bit encoding and stores the result into the target_buffer. 44 void EndEncoding(EncoderBuffer *target_buffer); 45 46 private: 47 void Clear(); 48 49 std::vector<uint64_t> bit_counts_; 50 std::vector<uint32_t> bits_; 51 uint32_t local_bits_; 52 uint32_t num_local_bits_; 53 }; 54 55 } // namespace draco 56 57 #endif // DRACO_COMPRESSION_BIT_CODERS_RANS_BIT_ENCODER_H_ 58