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#pragma once
#include <cstdint>
/** Common defines for compression */
#define DBMS_MAX_COMPRESSED_SIZE 0x40000000ULL /// 1GB
/** one byte for method, 4 bytes for compressed size, 4 bytes for uncompressed size */
#define COMPRESSED_BLOCK_HEADER_SIZE 9
namespace DB
{
/** The compressed block format is as follows:
*
* The first 16 bytes are the checksum from all other bytes of the block. Now only CityHash128 is used.
* In the future, you can provide other checksums, although it will not be possible to make them different in size.
*
* The next byte specifies the compression algorithm. Then everything depends on the algorithm.
*
* 0x82 - LZ4 or LZ4HC (they have the same format).
* Next 4 bytes - the size of the compressed data, taking into account the header; 4 bytes is the size of the uncompressed data.
*
* NOTE: Why is 0x82?
* Originally only QuickLZ was used. Then LZ4 was added.
* The high bit is set to distinguish from QuickLZ, and the second bit is set for compatibility,
* for the functions qlz_size_compressed, qlz_size_decompressed to work.
* Although now such compatibility is no longer relevant.
*
* 0x90 - ZSTD
*
* All sizes are little endian.
*/
enum class CompressionMethodByte : uint8_t
{
NONE = 0x02,
LZ4 = 0x82,
ZSTD = 0x90,
Multiple = 0x91,
Delta = 0x92,
T64 = 0x93,
DoubleDelta = 0x94,
Gorilla = 0x95,
AES_128_GCM_SIV = 0x96,
AES_256_GCM_SIV = 0x97,
FPC = 0x98,
DeflateQpl = 0x99,
};
}
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