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63 lines
2.0 KiB
C
63 lines
2.0 KiB
C
#ifndef LDM_H
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#define LDM_H
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#include <stddef.h> /* size_t */
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#include "mem.h" // from /lib/common/mem.h
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#define LDM_COMPRESS_SIZE 8
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#define LDM_DECOMPRESS_SIZE 8
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#define LDM_HEADER_SIZE ((LDM_COMPRESS_SIZE)+(LDM_DECOMPRESS_SIZE))
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typedef U32 offset_t;
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typedef U32 hash_t;
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typedef struct LDM_hashEntry LDM_hashEntry;
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typedef struct LDM_compressStats LDM_compressStats;
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typedef struct LDM_CCtx LDM_CCtx;
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/**
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* Compresses src into dst.
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*
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* NB: This currently ignores maxDstSize and assumes enough space is available.
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*
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* Block format (see lz4 documentation for more information):
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* github.com/lz4/lz4/blob/dev/doc/lz4_Block_format.md
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*
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* A block is composed of sequences. Each sequence begins with a token, which
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* is a one-byte value separated into two 4-bit fields.
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*
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* The first field uses the four high bits of the token and encodes the literal
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* length. If the field value is 0, there is no literal. If it is 15,
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* additional bytes are added (each ranging from 0 to 255) to the previous
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* value to produce a total length.
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*
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* Following the token and optional length bytes are the literals.
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*
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* Next are the 4 bytes representing the offset of the match (2 in lz4),
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* representing the position to copy the literals.
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*
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* The lower four bits of the token encode the match length. With additional
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* bytes added similarly to the additional literal length bytes after the offset.
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*
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* The last sequence is incomplete and stops right after the lieterals.
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*
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*/
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size_t LDM_compress(const void *src, size_t srcSize,
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void *dst, size_t maxDstSize);
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size_t LDM_decompress(const void *src, size_t srcSize,
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void *dst, size_t maxDstSize);
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/**
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* Reads the header from src and writes the compressed size and
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* decompressed size into compressSize and decompressSize respectively.
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*
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* NB: LDM_compress and LDM_decompress currently do not add/read headers.
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*/
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void LDM_readHeader(const void *src, U64 *compressSize,
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U64 *decompressSize);
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void LDM_test(void);
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#endif /* LDM_H */
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