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53 lines
1.5 KiB
C++
53 lines
1.5 KiB
C++
#pragma once
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#include <Common/PODArray.h>
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#include <IO/LZ4_decompress_faster.h>
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namespace DB
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{
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class ReadBuffer;
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/** Basic functionality for implementation of
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* CompressedReadBuffer, CompressedReadBufferFromFile and CachedCompressedReadBuffer.
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*/
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class CompressedReadBufferBase
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{
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protected:
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ReadBuffer * compressed_in;
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/// If 'compressed_in' buffer has whole compressed block - then use it. Otherwise copy parts of data to 'own_compressed_buffer'.
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PODArray<char> own_compressed_buffer;
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/// Points to memory, holding compressed block.
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char * compressed_buffer = nullptr;
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/// Don't checksum on decompressing.
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bool disable_checksum = false;
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LZ4::PerformanceStatistics lz4_stat;
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/// Read compressed data into compressed_buffer. Get size of decompressed data from block header. Checksum if need.
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/// Returns number of compressed bytes read.
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size_t readCompressedData(size_t & size_decompressed, size_t & size_compressed_without_checksum);
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void decompress(char * to, size_t size_decompressed, size_t size_compressed_without_checksum);
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public:
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/// 'compressed_in' could be initialized lazily, but before first call of 'readCompressedData'.
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CompressedReadBufferBase(ReadBuffer * in = nullptr);
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~CompressedReadBufferBase();
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/** Disable checksums.
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* For example, may be used when
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* compressed data is generated by client, that cannot calculate checksums, and fill checksums with zeros instead.
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*/
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void disableChecksumming()
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{
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disable_checksum = true;
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}
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};
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}
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