typedef struct Thwack Thwack;

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

enum
{
ThwStats = 8,
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 */

EWinBlocks = 22, /* blocks held in encoder window */
DWinBlocks = 32, /* blocks held in decoder window */
CompBlocks = 10, /* max blocks used to encode data */

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

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

struct Thwack
{
int slot; /* next block to use */
ThwBlock blocks[EWinBlocks];
ushort hash[EWinBlocks][HashSize];
uchar data[EWinBlocks][ThwMaxBlock];
};

struct UnthwBlock
{
ulong seq; /* sequence number for this data */
ushort maxoff; /* valid data in each block */
uchar *data;
};

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

void thwackinit(Thwack*);
void unthwackinit(Unthwack*);
int thwack(Thwack*, uchar *dst, uchar *src, int nsrc, ulong seq, ulong stats[ThwStats]);
void thwackack(Thwack*, ulong seq, ulong mask);
int unthwack(Unthwack*, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq);
ulong unthwackstate(Unthwack *ut, uchar *mask);