libavcodec/lzwenc.c File Reference

LZW encoder. More...

#include "avcodec.h"
#include "put_bits.h"
#include "lzw.h"

Go to the source code of this file.

Data Structures
struct	Code
	One code in hash table. More...
struct	LZWEncodeState
	LZW encode state. More...
Defines
#define	LZW_MAXBITS   12
#define	LZW_SIZTABLE   (1<<LZW_MAXBITS)
#define	LZW_HASH_SIZE   16411
#define	LZW_HASH_SHIFT   6
#define	LZW_PREFIX_EMPTY   -1
#define	LZW_PREFIX_FREE   -2
Functions
static int	hash (int head, const int add)
	Hash function adding character.
static int	hashNext (int head, const int offset)
	Hash function calculates next hash value.
static int	hashOffset (const int head)
	Hash function calculates hash offset.
static void	writeCode (LZWEncodeState *s, int c)
	Write one code to stream.
static int	findCode (LZWEncodeState *s, uint8_t c, int hash_prefix)
	Find LZW code for block.
static void	addCode (LZWEncodeState *s, uint8_t c, int hash_prefix, int hash_code)
	Add block to LZW code table.
static void	clearTable (LZWEncodeState *s)
	Clear LZW code table.
static int	writtenBytes (LZWEncodeState *s)
	Calculate number of bytes written.
void	ff_lzw_encode_init (LZWEncodeState *s, uint8_t *outbuf, int outsize, int maxbits, enum FF_LZW_MODES mode, void(*lzw_put_bits)(PutBitContext *, int, unsigned))
	Initialize LZW encoder.
int	ff_lzw_encode (LZWEncodeState *s, const uint8_t *inbuf, int insize)
	LZW main compress function.
int	ff_lzw_encode_flush (LZWEncodeState *s, void(*lzw_flush_put_bits)(PutBitContext *))
	Write end code and flush bitstream.
Variables
const int	ff_lzw_encode_state_size = sizeof(LZWEncodeState)

---

Detailed Description

LZW encoder.

Author:

Bartlomiej Wolowiec

Definition in file lzwenc.c.

---

Define Documentation

#define LZW_HASH_SHIFT   6

Definition at line 35 of file lzwenc.c.

Referenced by hash().

#define LZW_HASH_SIZE   16411

Definition at line 34 of file lzwenc.c.

Referenced by clearTable(), hash(), hashNext(), and hashOffset().

#define LZW_MAXBITS   12

Definition at line 32 of file lzwenc.c.

#define LZW_PREFIX_EMPTY   -1

Definition at line 37 of file lzwenc.c.

Referenced by clearTable(), ff_lzw_encode(), and ff_lzw_encode_init().

#define LZW_PREFIX_FREE   -2

Definition at line 38 of file lzwenc.c.

Referenced by clearTable(), ff_lzw_encode(), and findCode().

#define LZW_SIZTABLE   (1<<LZW_MAXBITS)

Definition at line 33 of file lzwenc.c.

---

Function Documentation

static void addCode	(	LZWEncodeState *	s,
		uint8_t	c,
		int	hash_prefix,
		int	hash_code
	)			[inline, static]

Add block to LZW code table.

Parameters:

	s	LZW state
	c	Last character in block
	hash_prefix	LZW code for prefix
	hash_code	LZW code for bytes block

Definition at line 148 of file lzwenc.c.

Referenced by ff_lzw_encode().

static void clearTable

(

LZWEncodeState *

s

)

[static]

Clear LZW code table.

Parameters:

s

LZW state

Definition at line 164 of file lzwenc.c.

Referenced by ff_lzw_encode().

int ff_lzw_encode	(	LZWEncodeState *	s,
		const uint8_t *	inbuf,
		int	insize
	)

LZW main compress function.

Parameters:

	s	LZW state
	inbuf	Input buffer
	insize	Size of input buffer

Returns:

Number of bytes written or -1 on error

Definition at line 226 of file lzwenc.c.

Referenced by encode_strip(), and gif_image_write_image().

int ff_lzw_encode_flush	(	LZWEncodeState *	s,
		void(*)(PutBitContext *)	lzw_flush_put_bits
	)

Write end code and flush bitstream.

Parameters:

s

LZW state

Returns:

Number of bytes written or -1 on error

Definition at line 259 of file lzwenc.c.

void ff_lzw_encode_init	(	LZWEncodeState *	s,
		uint8_t *	outbuf,
		int	outsize,
		int	maxbits,
		enum FF_LZW_MODES	mode,
		void(*)(PutBitContext *, int, unsigned)	lzw_put_bits
	)

Initialize LZW encoder.

Please set s->clear_code, s->end_code and s->maxbits before run.

Parameters:

	s	LZW state
	outbuf	Output buffer
	outsize	Size of output buffer
	maxbits	Maximum length of code

Definition at line 201 of file lzwenc.c.

static int findCode	(	LZWEncodeState *	s,
		uint8_t	c,
		int	hash_prefix
	)			[inline, static]

Find LZW code for block.

Parameters:

	s	LZW state
	c	Last character in block
	hash_prefix	LZW code for prefix

Returns:

LZW code for block or -1 if not found in table

Definition at line 126 of file lzwenc.c.

Referenced by ff_lzw_encode().

static int hash	(	int	head,
		const int	add
	)			[inline, static]

Hash function adding character.

Parameters:

	head	LZW code for prefix
	add	Character to add

Returns:

New hash value

Definition at line 74 of file lzwenc.c.

Referenced by adpcm_compress_trellis(), bidir_refine(), clearTable(), ff_lzw_encode(), findCode(), make_digest_auth(), and sap_fetch_packet().

static int hashNext	(	int	head,
		const int	offset
	)			[inline, static]

Hash function calculates next hash value.

Parameters:

	head	Actual hash code
	offset	Offset calculated by hashOffset

Returns:

New hash value

Definition at line 89 of file lzwenc.c.

Referenced by findCode().

static int hashOffset

(

const int

head

)

[inline, static]

Hash function calculates hash offset.

Parameters:

head

Actual hash code

Returns:

Hash offset

Definition at line 102 of file lzwenc.c.

Referenced by findCode().

static void writeCode	(	LZWEncodeState *	s,
		int	c
	)			[inline, static]

Write one code to stream.

Parameters:

	s	LZW state
	c	code to write

Definition at line 112 of file lzwenc.c.

Referenced by clearTable(), ff_lzw_encode(), and ff_lzw_encode_flush().

static int writtenBytes

(

LZWEncodeState *

s

)

[static]

Calculate number of bytes written.

Parameters:

s

LZW encode state

Returns:

Number of bytes written

Definition at line 187 of file lzwenc.c.

Referenced by ff_lzw_encode(), and ff_lzw_encode_flush().

---

Variable Documentation

const int ff_lzw_encode_state_size = sizeof(LZWEncodeState)

Definition at line 66 of file lzwenc.c.

Referenced by gif_encode_init().