fastlz.c File Reference

#include "fastlz.h"
#include <inttypes.h>
#include "fastlz.h"

Defines
#define	FASTLZ_SAFE
#define	FASTLZ_EXPECT_CONDITIONAL(c)   (c)
#define	FASTLZ_UNEXPECT_CONDITIONAL(c)   (c)
#define	FASTLZ_INLINE
#define	FASTLZ_STRICT_ALIGN
#define	MAX_COPY   32
#define	MAX_LEN   264
#define	MAX_DISTANCE   8192
#define	FASTLZ_READU16(p)   ((p)[0] | (p)[1]<<8)
#define	HASH_LOG   13
#define	HASH_SIZE   (1<< HASH_LOG)
#define	HASH_MASK   (HASH_SIZE-1)
#define	HASH_FUNCTION(v, p)   { v = FASTLZ_READU16(p); v ^= FASTLZ_READU16(p+1)^(v>>(16-HASH_LOG));v &= HASH_MASK; }
#define	FASTLZ_LEVEL   1
#define	FASTLZ_COMPRESSOR   fastlz1_compress
#define	FASTLZ_DECOMPRESSOR   fastlz1_decompress
#define	FASTLZ_LEVEL   2
#define	MAX_DISTANCE   8191
#define	MAX_FARDISTANCE   (65535+MAX_DISTANCE-1)
#define	FASTLZ_COMPRESSOR   fastlz2_compress
#define	FASTLZ_DECOMPRESSOR   fastlz2_decompress
Functions
int	fastlz_compress (const void *input, int length, void *output)
int	fastlz_compress_level (int level, const void *input, int length, void *output)
int	fastlz_decompress (const void *input, int length, void *output, int maxout)
static FASTLZ_INLINE int	FASTLZ_COMPRESSOR (const void *input, int length, void *output)
static FASTLZ_INLINE int	FASTLZ_DECOMPRESSOR (const void *input, int length, void *output, int maxout)

---

Define Documentation

#define FASTLZ_COMPRESSOR   fastlz2_compress

#define FASTLZ_COMPRESSOR   fastlz1_compress

#define FASTLZ_DECOMPRESSOR   fastlz2_decompress

#define FASTLZ_DECOMPRESSOR   fastlz1_decompress

#define FASTLZ_EXPECT_CONDITIONAL

(

c

)

(c)

#define FASTLZ_INLINE

#define FASTLZ_LEVEL   2

#define FASTLZ_LEVEL   1

#define FASTLZ_READU16

(

p

)

((p)[0] | (p)[1]<<8)

#define FASTLZ_SAFE

#define FASTLZ_STRICT_ALIGN

#define FASTLZ_UNEXPECT_CONDITIONAL

(

c

)

(c)

#define HASH_FUNCTION	(	v,
		p		)	{ v = FASTLZ_READU16(p); v ^= FASTLZ_READU16(p+1)^(v>>(16-HASH_LOG));v &= HASH_MASK; }

#define HASH_LOG   13

#define HASH_MASK   (HASH_SIZE-1)

#define HASH_SIZE   (1<< HASH_LOG)

#define MAX_COPY   32

#define MAX_DISTANCE   8191

#define MAX_DISTANCE   8192

#define MAX_FARDISTANCE   (65535+MAX_DISTANCE-1)

#define MAX_LEN   264

---

Function Documentation

int fastlz_compress	(	const void *	input,
		int	length,
		void *	output
	)

Compress a block of data in the input buffer and returns the size of compressed block. The size of input buffer is specified by length. The minimum input buffer size is 16.

The output buffer must be at least 5% larger than the input buffer and can not be smaller than 66 bytes.

If the input is not compressible, the return value might be larger than length (input buffer size).

The input buffer and the output buffer can not overlap.

Referenced by fstWriterFlushContext().

{
  /* for short block, choose fastlz1 */
  if(length < 65536)
    return fastlz1_compress(input, length, output);

  /* else... */
  return fastlz2_compress(input, length, output);
}

int fastlz_compress_level	(	int	level,
		const void *	input,
		int	length,
		void *	output
	)

Compress a block of data in the input buffer and returns the size of compressed block. The size of input buffer is specified by length. The minimum input buffer size is 16.

The output buffer must be at least 5% larger than the input buffer and can not be smaller than 66 bytes.

If the input is not compressible, the return value might be larger than length (input buffer size).

The input buffer and the output buffer can not overlap.

Compression level can be specified in parameter level. At the moment, only level 1 and level 2 are supported. Level 1 is the fastest compression and generally useful for short data. Level 2 is slightly slower but it gives better compression ratio.

Note that the compressed data, regardless of the level, can always be decompressed using the function fastlz_decompress above.

{
  if(level == 1)
    return fastlz1_compress(input, length, output);
  if(level == 2)
    return fastlz2_compress(input, length, output);

  return 0;
}

static FASTLZ_INLINE int FASTLZ_COMPRESSOR	(	const void *	input,
		int	length,
		void *	output
	)			[static]

int fastlz_decompress	(	const void *	input,
		int	length,
		void *	output,
		int	maxout
	)

Decompress a block of compressed data and returns the size of the decompressed block. If error occurs, e.g. the compressed data is corrupted or the output buffer is not large enough, then 0 (zero) will be returned instead.

The input buffer and the output buffer can not overlap.

Decompression is memory safe and guaranteed not to write the output buffer more than what is specified in maxout.

References flzuint8.

Referenced by fstReaderIterBlocks().

{
  /* magic identifier for compression level */
  int level = ((*(const flzuint8*)input) >> 5) + 1;

  if(level == 1)
    return fastlz1_decompress(input, length, output, maxout);
  if(level == 2)
    return fastlz2_decompress(input, length, output, maxout);

  /* unknown level, trigger error */
  return 0;
}

static FASTLZ_INLINE int FASTLZ_DECOMPRESSOR	(	const void *	input,
		int	length,
		void *	output,
		int	maxout
	)			[static]