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98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
#pragma once
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#include <memory>
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#include <boost/noncopyable.hpp>
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#include <Compression/CompressionInfo.h>
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#include <common/types.h>
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#include <Parsers/IAST.h>
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#include <Common/SipHash.h>
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namespace DB
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{
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class ICompressionCodec;
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using CompressionCodecPtr = std::shared_ptr<ICompressionCodec>;
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using Codecs = std::vector<CompressionCodecPtr>;
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class IDataType;
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/**
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* Represents interface for compression codecs like LZ4, ZSTD, etc.
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*/
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class ICompressionCodec : private boost::noncopyable
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{
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public:
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virtual ~ICompressionCodec() = default;
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/// Byte which indicates codec in compressed file
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virtual uint8_t getMethodByte() const = 0;
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/// Codec description, for example "ZSTD(2)" or "LZ4,LZ4HC(5)"
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virtual ASTPtr getCodecDesc() const;
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/// Codec description with "CODEC" prefix, for example "CODEC(ZSTD(2))" or
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/// "CODEC(LZ4,LZ4HC(5))"
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ASTPtr getFullCodecDesc() const;
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/// Hash, that depends on codec ast and optional parameters like data type
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virtual void updateHash(SipHash & hash) const = 0;
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UInt64 getHash() const;
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/// Compressed bytes from uncompressed source to dest. Dest should preallocate memory
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UInt32 compress(const char * source, UInt32 source_size, char * dest) const;
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/// Decompress bytes from compressed source to dest. Dest should preallocate memory
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UInt32 decompress(const char * source, UInt32 source_size, char * dest) const;
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/// Number of bytes, that will be used to compress uncompressed_size bytes with current codec
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virtual UInt32 getCompressedReserveSize(UInt32 uncompressed_size) const
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{
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return getHeaderSize() + getMaxCompressedDataSize(uncompressed_size);
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}
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/// Some codecs (LZ4, for example) require additional bytes at end of buffer
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virtual UInt32 getAdditionalSizeAtTheEndOfBuffer() const { return 0; }
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/// Size of header in compressed data on disk
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static constexpr UInt8 getHeaderSize() { return COMPRESSED_BLOCK_HEADER_SIZE; }
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/// Read size of compressed block from compressed source
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static UInt32 readCompressedBlockSize(const char * source);
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/// Read size of decompressed block from compressed source
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static UInt32 readDecompressedBlockSize(const char * source);
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/// Read method byte from compressed source
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static uint8_t readMethod(const char * source);
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/// Return true if this codec actually compressing something. Otherwise it can be just transformation that helps compression (e.g. Delta).
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virtual bool isCompression() const = 0;
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/// Is it a generic compression algorithm like lz4, zstd. Usually it does not make sense to apply generic compression more than single time.
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virtual bool isGenericCompression() const = 0;
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/// If it does nothing.
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virtual bool isNone() const { return false; }
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protected:
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/// Return size of compressed data without header
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virtual UInt32 getMaxCompressedDataSize(UInt32 uncompressed_size) const { return uncompressed_size; }
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/// Actually compress data, without header
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virtual UInt32 doCompressData(const char * source, UInt32 source_size, char * dest) const = 0;
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/// Actually decompress data without header
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virtual void doDecompressData(const char * source, UInt32 source_size, char * dest, UInt32 uncompressed_size) const = 0;
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/// Construct and set codec description from codec name and arguments. Must be called in codec constructor.
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void setCodecDescription(const String & name, const ASTs & arguments = {});
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private:
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ASTPtr full_codec_desc;
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};
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}
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