harvey/sys/src/cmd/ip/ppp/thwack.h

/*
 * This file is part of the UCB release of Plan 9. It is subject to the license
 * terms in the LICENSE file found in the top-level directory of this
 * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
 * part of the UCB release of Plan 9, including this file, may be copied,
 * modified, propagated, or distributed except according to the terms contained
 * in the LICENSE file.
 */

typedef struct Thwack		Thwack;
typedef struct Unthwack		Unthwack;
typedef struct ThwBlock		ThwBlock;
typedef struct UnthwBlock	UnthwBlock;

enum
{
	ThwStats	= 8,
	ThwErrLen	= 64,		/* max length of error message from thwack or unthwack */
	ThwMaxBlock	= 1600,		/* max size of compressible block */

	HashLog		= 12,
	HashSize	= 1<<HashLog,
	HashMask	= HashSize - 1,

	MinMatch	= 3,		/* shortest match possible */

	MaxOff		= 8,
	OffBase		= 6,

	MinDecode	= 8,		/* minimum bits to decode a match or lit; >= 8 */

	CompBlocks	= 10,		/* max blocks used to encode data */
	EWinBlocks	= 64,		/* blocks held in encoder window */
	DWinBlocks	= EWinBlocks,	/* blocks held in decoder window */

	MaxSeqMask	= 8,		/* number of bits in coding block mask */
	MaxSeqStart	= 256		/* max offset of initial coding block */
};

struct ThwBlock
{
	uint32_t	seq;			/* sequence number for this data */
	uint8_t	acked;			/* ok to use this block; the decoder has it */
	uint16_t	begin;			/* time of first byte in hash */
	uint8_t	*edata;			/* last byte of valid data */
	uint16_t	maxoff;			/* time of last valid hash entry */
	uint16_t	*hash;
	uint8_t	*data;
};

struct Thwack
{
	QLock		acklock;	/* locks slot, blocks[].(acked|seq) */
	int		slot;		/* next block to use */
	ThwBlock	blocks[EWinBlocks];
	uint16_t		hash[EWinBlocks][HashSize];
	Block		*data[EWinBlocks];
};

struct UnthwBlock
{
	uint32_t	seq;			/* sequence number for this data */
	uint16_t	maxoff;			/* valid data in each block */
	uint8_t	*data;
};

struct Unthwack
{
	int		slot;		/* next block to use */
	char		err[ThwErrLen];
	UnthwBlock	blocks[DWinBlocks];
	uint8_t		data[DWinBlocks][ThwMaxBlock];
};

void	thwackinit(Thwack*);
void	thwackcleanup(Thwack *tw);
void	unthwackinit(Unthwack*);
int	thwack(Thwack*, int mustadd, uint8_t *dst, int ndst, Block *bsrc,
		  uint32_t seq, uint32_t stats[ThwStats]);
void	thwackack(Thwack*, uint32_t seq, uint32_t mask);
int	unthwack(Unthwack*, uint8_t *dst, int ndst, uint8_t *src, int nsrc,
		    uint32_t seq);
uint32_t	unthwackstate(Unthwack *ut, uint8_t *mask);
int	unthwackadd(Unthwack *ut, uint8_t *src, int nsrc, uint32_t seq);