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if (window[i] != buffer[j])

break;

match++;

i++;

j++;

}

/**************************************************************************

* *

* Keep track of the offset, length, and next symbol for the best match. *

* *

**************************************************************************/

if (match > longest) {

*offset = k;

longest = match;

*next = buffer[j];

}

}

return longest;

}

/*****************************************************************************

* *

* ----------------------------- lz77_compress ---------------------------- *

* *

*****************************************************************************/

int lz77_compress(const unsigned char *original, unsigned char **compressed,

int size) {

unsigned char window[LZ77_WINDOW_SIZE],

buffer[LZ77_BUFFER_SIZE],

*comp,

*temp,

next;

int offset,

length,

remaining,

hsize,

ipos,

opos,

tpos,

i;

/*****************************************************************************

* *

* Make the pointer to the compressed data not valid until later. *

* *

*****************************************************************************/

*compressed = NULL;

/*****************************************************************************

* *

* Write the header information. *

* *

*****************************************************************************/

hsize = sizeof(int);

if ((comp = (unsigned char *)malloc(hsize)) == NULL)

return -1;

memcpy(comp, &size, sizeof(int));

/*****************************************************************************

* *

* Initialize the sliding window and the look-ahead buffer. *

* *

*****************************************************************************/

memset(window, 0, LZ77_WINDOW_SIZE);

memset(buffer, 0, LZ77_BUFFER_SIZE);

/*****************************************************************************

* *

* Load the look-ahead buffer. *

* *

*****************************************************************************/

ipos = 0;

for (i = 0; i < LZ77_BUFFER_SIZE && ipos < size; i++) {

buffer[i] = original[ipos];

ipos++;

}

/*****************************************************************************

* *

* Compress the data. *

* *

*****************************************************************************/

opos = hsize * 8;

remaining = size;

while (remaining > 0) {

if ((length = compare_win(window, buffer, &offset, &next)) != 0) {

/***********************************************************************

* *

* Encode a phrase token. *

* *

***********************************************************************/

token = 0x00000001 << (LZ77_PHRASE_BITS - 1);

/***********************************************************************

* *

* Set the offset where the match was found in the sliding window. *

* *

***********************************************************************/

token = token | (offset << (LZ77_PHRASE_BITS - LZ77_TYPE_BITS -

LZ77_WINOFF_BITS));

/***********************************************************************

* *

* Set the length of the match. *

* *

***********************************************************************/

token = token | (length << (LZ77_PHRASE_BITS - LZ77_TYPE_BITS -

LZ77_WINOFF_BITS - LZ77_BUFLEN_BITS));

/***********************************************************************

* *

* Set the next symbol in the look-ahead buffer after the match. *

* *

***********************************************************************/

token = token | next;

/***********************************************************************

* *

* Set the number of bits in the token. *

* *

***********************************************************************/

tbits = LZ77_PHRASE_BITS;

}

else {

/***********************************************************************

* *

* Encode a symbol token. *

* *

***********************************************************************/