lzwenc.c File Reference

LZW encoder. More...

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

Macros
#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.

Macro Definition Documentation

#define LZW_MAXBITS   12

Definition at line 33 of file lzwenc.c.

Referenced by ff_lzw_encode_init().

#define LZW_SIZTABLE   (1<<LZW_MAXBITS)

Definition at line 34 of file lzwenc.c.

#define LZW_HASH_SIZE   16411

Definition at line 35 of file lzwenc.c.

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

#define LZW_HASH_SHIFT   6

Definition at line 36 of file lzwenc.c.

Referenced by hash().

#define LZW_PREFIX_EMPTY   -1

Definition at line 38 of file lzwenc.c.

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

#define LZW_PREFIX_FREE   -2

Definition at line 39 of file lzwenc.c.

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

Function Documentation

static int hash ( int  head, const int  add  )

inlinestatic

Hash function adding character.

Parameters

head	LZW code for prefix
add	Character to add

Returns

New hash value

Definition at line 75 of file lzwenc.c.

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

static int hashNext ( int  head, const int  offset  )

inlinestatic

Hash function calculates next hash value.

Parameters

head	Actual hash code
offset	Offset calculated by hashOffset

Returns

New hash value

Definition at line 90 of file lzwenc.c.

Referenced by findCode().

static int hashOffset ( const int  head )

inlinestatic

Hash function calculates hash offset.

Parameters

head	Actual hash code

Returns

Hash offset

Definition at line 103 of file lzwenc.c.

Referenced by findCode().

static void writeCode ( LZWEncodeState *  s, int  c  )

inlinestatic

Write one code to stream.

Parameters

s	LZW state
c	code to write

Definition at line 113 of file lzwenc.c.

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

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

inlinestatic

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 127 of file lzwenc.c.

Referenced by ff_lzw_encode().

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

inlinestatic

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 149 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 165 of file lzwenc.c.

Referenced by ff_lzw_encode().

static int writtenBytes ( LZWEncodeState *  s )

static

Calculate number of bytes written.

Parameters

s	LZW encode state

Returns

Number of bytes written

Definition at line 188 of file lzwenc.c.

Referenced by ff_lzw_encode(), and ff_lzw_encode_flush().

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 202 of file lzwenc.c.

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 227 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 260 of file lzwenc.c.

Variable Documentation

const int ff_lzw_encode_state_size = sizeof(LZWEncodeState)

Definition at line 67 of file lzwenc.c.

Referenced by encode_frame(), and gif_encode_init().