lz4_dec_internal.h File Reference

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Macros
#define	LZ4_DECOMPRESS_INPLACE_MARGIN(compressed_size)   (((compressed_size) >> 8) + 32)
	Calculate the margin required for in-place decompression.
#define	DECOMPRESS_LZ4_STATE_SIZE   176
	Size of the LZ4 decompressor state structure, in bytes.

Functions
int	decompress_lz4_full_inplace (const uint8_t *src, size_t src_size, uint8_t *dst, size_t dst_size)
	Decompress a block of LZ4 data (mem to mem).
void	decompress_lz4_init (void *state, int fd, int winsize)
	Initialize the LZ4 decompressor state.
ssize_t	decompress_lz4_read (void *state, void *buf, size_t len)
	Read decompressed data from the LZ4 stream.
void	decompress_lz4_reset (void *state)
	Reset the LZ4 decompressor state.
void *	decompress_lz4_full (const char *fn, FILE *fp, size_t cmp_size, size_t size)
	Decompress a full LZ4 file from a FILE pointer.

Detailed Description

Author

Giovanni Bajo giova.nosp@m.nnib.nosp@m.ajo@g.nosp@m.mail.nosp@m..com

Macro Definition Documentation

LZ4_DECOMPRESS_INPLACE_MARGIN

#define LZ4_DECOMPRESS_INPLACE_MARGIN

(

compressed_size

)

(((compressed_size) >> 8) + 32)

Calculate the margin required for in-place decompression.

It is possible to perform in-place decompression of LZ4 data: to do so, allocate a buffer large enough to hold the decompressed data, plus some margin calculated through this function. Then, read the compressed data at the end of the buffer. Finally, call the decompression function (see below).

Example:

// Allocate a buffer large enough to hold the decompressed data,
// pluse the inplace margin.
int buf_size = decompressed_size + LZ4_DECOMPRESS_INPLACE_MARGIN(compressed_size);
void *buf = malloc(buf_size);
 
// Read compressed data at the end of the buffer
fread(buf + buf_size - compressed_size, 1, compressed_size, fp);
 
// Decompress
decompress_lz4_full_mem(
    buf + buf_size - compressed_size, compressed_size,
    buf, decompressed_size,
    false);

Function Documentation

decompress_lz4_full_inplace()

int decompress_lz4_full_inplace	(	const uint8_t *	src,
		size_t	src_size,
		uint8_t *	dst,
		size_t	dst_size
	)

Decompress a block of LZ4 data (mem to mem).

This function run a LZ4 decompressor on a block of data, from memory to memory.

LZ4 is much faster than PI DMA. To benefit even more from this, it is possible to actually run this function in parallel with the DMA transfer, "racing" with it. If called with dma_race set to true, the function will assume that the source buffer is currently being DMAed into memory, and will throttle itself to never read past the current DMA position.

In addition to this, it is possible to in-place decompress a block of data. See LZ4_DECOMPRESS_INPLACE_MARGIN for more information.

Parameters

src	Pointer to source buffer (compressed data)
src_size	Size of the compressed data in bytes
dst	Pointer to destination buffer (decompressed data)
dst_size	Size of the destination buffer in bytes

Returns

int Number of bytes decompressed, or -1 on error.

decompress_lz4_init()

void decompress_lz4_init	(	void *	state,
		int	fd,
		int	winsize
	)

Initialize the LZ4 decompressor state.

Parameters

state	Pointer to the decompressor state buffer.
fd	File descriptor to read compressed data from.
winsize	Window size for the decompressor.

decompress_lz4_read()

ssize_t decompress_lz4_read	(	void *	state,
		void *	buf,
		size_t	len
	)

Read decompressed data from the LZ4 stream.

Parameters

state	Pointer to the decompressor state buffer.
buf	Buffer to store decompressed data.
len	Number of bytes to read.

Returns

Number of bytes read, or -1 on error.

decompress_lz4_reset()

void decompress_lz4_reset

(

void *

state

)

Reset the LZ4 decompressor state.

Parameters

state

Pointer to the decompressor state buffer.

decompress_lz4_full()

void * decompress_lz4_full	(	const char *	fn,
		FILE *	fp,
		size_t	cmp_size,
		size_t	size
	)

Decompress a full LZ4 file from a FILE pointer.

Parameters

fn	Filename (for error messages).
fp	FILE pointer to read compressed data from.
cmp_size	Size of the compressed data.
size	Size of the decompressed data.

Returns

Pointer to the decompressed data buffer, or NULL on error.