ClickHouse/dbms/Compression/ICompressionCodec.h
Ivan 97f2a2213e
Move all folders inside /dbms one level up (#9974)
* Move some code outside dbms/src folder
* Fix paths
2020-04-02 02:51:21 +03:00

75 lines
2.7 KiB
C++

#pragma once
#include <memory>
#include <IO/ReadBuffer.h>
#include <IO/WriteBuffer.h>
#include <IO/BufferWithOwnMemory.h>
#include <DataTypes/IDataType.h>
#include <boost/noncopyable.hpp>
#include <IO/UncompressedCache.h>
#include <Compression/LZ4_decompress_faster.h>
#include <Compression/CompressionInfo.h>
namespace DB
{
class ICompressionCodec;
using CompressionCodecPtr = std::shared_ptr<ICompressionCodec>;
using Codecs = std::vector<CompressionCodecPtr>;
/**
* Represents interface for compression codecs like LZ4, ZSTD, etc.
*/
class ICompressionCodec : private boost::noncopyable
{
public:
virtual ~ICompressionCodec() = default;
/// Byte which indicates codec in compressed file
virtual uint8_t getMethodByte() const = 0;
/// Codec description, for example "ZSTD(2)" or "LZ4,LZ4HC(5)"
virtual String getCodecDesc() const = 0;
/// Compressed bytes from uncompressed source to dest. Dest should preallocate memory
UInt32 compress(const char * source, UInt32 source_size, char * dest) const;
/// Decompress bytes from compressed source to dest. Dest should preallocate memory
UInt32 decompress(const char * source, UInt32 source_size, char * dest) const;
/// Number of bytes, that will be used to compress uncompressed_size bytes with current codec
virtual UInt32 getCompressedReserveSize(UInt32 uncompressed_size) const { return getHeaderSize() + getMaxCompressedDataSize(uncompressed_size); }
/// Some codecs (LZ4, for example) require additional bytes at end of buffer
virtual UInt32 getAdditionalSizeAtTheEndOfBuffer() const { return 0; }
/// Size of header in compressed data on disk
static constexpr UInt8 getHeaderSize() { return COMPRESSED_BLOCK_HEADER_SIZE; }
/// Read size of compressed block from compressed source
static UInt32 readCompressedBlockSize(const char * source);
/// Read size of decompressed block from compressed source
static UInt32 readDecompressedBlockSize(const char * source);
/// Read method byte from compressed source
static uint8_t readMethod(const char * source);
/// Some codecs may use information about column type which appears after codec creation
virtual void useInfoAboutType(DataTypePtr /* data_type */) { }
protected:
/// Return size of compressed data without header
virtual UInt32 getMaxCompressedDataSize(UInt32 uncompressed_size) const { return uncompressed_size; }
/// Actually compress data, without header
virtual UInt32 doCompressData(const char * source, UInt32 source_size, char * dest) const = 0;
/// Actually decompress data without header
virtual void doDecompressData(const char * source, UInt32 source_size, char * dest, UInt32 uncompressed_size) const = 0;
};
}