lzwenc.c File Reference

---

Detailed Description

LZW encoder.

Author:

Bartlomiej Wolowiec

Definition in file lzwenc.c.

Go to the source code of this file.

Classes
struct	Code
	One code in hash table. More...
struct	LZWEncodeState
	LZW encode state. More...
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)
	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)
	Write end code and flush bitstream.
Variables
const int	ff_lzw_encode_state_size = sizeof(LZWEncodeState)

---

Function Documentation

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 72 of file lzwenc.c.

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

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 87 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 100 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 110 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
	)			[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 124 of file lzwenc.c.

Referenced by ff_lzw_encode().

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 146 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 162 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 185 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
	)

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 199 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 220 of file lzwenc.c.

Referenced by encode_strip().

int ff_lzw_encode_flush

(

LZWEncodeState *

s

)

Write end code and flush bitstream.

Parameters:

s

LZW state

Returns:

Number of bytes written or -1 on error

Definition at line 253 of file lzwenc.c.

---

Variable Documentation

const int ff_lzw_encode_state_size = sizeof(LZWEncodeState)

Definition at line 64 of file lzwenc.c.