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104 lines
3.6 KiB
C++
104 lines
3.6 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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#ifndef DRACO_CORE_ENCODER_BUFFER_H_
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#define DRACO_CORE_ENCODER_BUFFER_H_
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#include <memory>
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#include <vector>
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#include "core/bit_coder.h"
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namespace draco {
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// Class representing a buffer that can be used for either for byte-aligned
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// encoding of arbitrary data structures or for encoding of varialble-length
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// bit data.
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class EncoderBuffer {
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public:
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EncoderBuffer();
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void Clear();
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void Resize(int64_t nbytes);
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// Start encoding a bit sequence. A maximum size of the sequence needs to
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// be known upfront.
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// If encode_size is true, the size of encoded bit sequence is stored before
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// the sequence. Decoder can then use this size to skip over the bit sequence
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// if needed.
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// Returns false on error.
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bool StartBitEncoding(int64_t required_bits, bool encode_size);
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// End the encoding of the bit sequence and return to the default byte-aligned
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// encoding.
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void EndBitEncoding();
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// Encode up to 32 bits into the buffer. Can be called only in between
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// StartBitEncoding and EndBitEncoding. Otherwise returns false.
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// TODO(hemmer): Swap arguments to make it consistent with DecoderBuffer.
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bool EncodeBits32(uint32_t value, int nbits) {
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if (!bit_encoder_active())
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return false;
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bit_encoder_->PutBits(value, nbits);
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return true;
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}
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// Encode an arbitrary data type.
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// Can be used only when we are not encoding a bit-sequence.
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// Returns false when the value couldn't be encoded.
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template <typename T>
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bool Encode(const T &data) {
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if (bit_encoder_active())
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return false;
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const uint8_t *src_data = reinterpret_cast<const uint8_t *>(&data);
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buffer_.insert(buffer_.end(), src_data, src_data + sizeof(T));
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return true;
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}
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bool Encode(const void *data, size_t data_size) {
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if (bit_encoder_active())
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return false;
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const uint8_t *src_data = reinterpret_cast<const uint8_t *>(data);
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buffer_.insert(buffer_.end(), src_data, src_data + data_size);
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return true;
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}
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bool bit_encoder_active() const { return bit_encoder_reserved_bytes_ > 0; }
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const char *data() const { return buffer_.data(); }
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size_t size() const { return buffer_.size(); }
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std::vector<char> *buffer() { return &buffer_; }
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BitEncoder *bit_encoder() { return bit_encoder_.get(); }
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private:
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// All data is stored in this vector.
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std::vector<char> buffer_;
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// Bit encoder is used when encoding variable-length bit data.
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// TODO(ostava): Currently encoder needs to be recreated each time
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// StartBitEncoding method is called. This is not necessary if BitEncoder
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// supported reset function which can easily added but let's leave that for
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// later.
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std::unique_ptr<BitEncoder> bit_encoder_;
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// The number of bytes reserved for bit encoder.
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// Values > 0 indicate we are in the bit encoding mode.
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int64_t bit_encoder_reserved_bytes_;
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// Flag used indicating that we need to store the length of the currently
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// processed bit sequence.
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bool encode_bit_sequence_size_;
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};
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} // namespace draco
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#endif // DRACO_CORE_ENCODER_BUFFER_H_
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