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89 lines
2.5 KiB
C++
89 lines
2.5 KiB
C++
// Copyright 2016 The Draco Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// File provides basic classes and functions for rANS coding.
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#ifndef DRACO_CORE_ADAPTIVE_RANS_CODING_H_
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#define DRACO_CORE_ADAPTIVE_RANS_CODING_H_
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#include <vector>
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#include "core/ans.h"
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#include "core/decoder_buffer.h"
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#include "core/encoder_buffer.h"
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namespace draco {
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// Class for adaptive encoding a sequence of bits using rANS.
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class AdaptiveRAnsBitEncoder {
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public:
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AdaptiveRAnsBitEncoder();
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~AdaptiveRAnsBitEncoder();
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// Must be called before any Encode* function is called.
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void StartEncoding();
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// Encode one bit. If |bit| is true encode a 1, otherwise encode a 0.
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void EncodeBit(bool bit) { bits_.push_back(bit); }
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// Encode |nibts| of |value|, starting from the least significant bit.
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// |nbits| must be > 0 and <= 32.
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void EncodeBits32(int nbits, uint32_t value) {
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DCHECK_EQ(true, nbits <= 32);
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DCHECK_EQ(true, nbits > 0);
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uint32_t selector = (1 << (nbits - 1));
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while (selector) {
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EncodeBit(value & selector);
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selector = selector >> 1;
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}
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}
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// Ends the bit encoding and stores the result into the target_buffer.
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void EndEncoding(EncoderBuffer *target_buffer);
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private:
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void Clear();
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std::vector<bool> bits_;
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};
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// Class for decoding a sequence of bits that were encoded with
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// AdaptiveRAnsBitEncoder.
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class AdaptiveRAnsBitDecoder {
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public:
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AdaptiveRAnsBitDecoder();
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~AdaptiveRAnsBitDecoder();
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// Sets |source_buffer| as the buffer to decode bits from.
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void StartDecoding(DecoderBuffer *source_buffer);
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// Decode one bit. Returns true if the bit is a 1, otherwsie false.
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bool DecodeNextBit();
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// Decode the next |nbits| and return the sequence in |value|. |nbits| must be
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// > 0 and <= 32.
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void DecodeBits32(int nbits, uint32_t *value);
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void EndDecoding() {}
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private:
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void Clear();
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AnsDecoder ans_decoder_;
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double p0_f_;
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};
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} // namespace draco
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#endif // DRACO_CORE_ADAPTIVE_RANS_CODING_H_
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