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/**************************************************************
LZSS.C -- A Data Compression Program
(tab = 4 spaces)
***************************************************************
4/6/1989 Haruhiko Okumura
Use, distribute, and modify this program freely.
Please send me your improved versions.
PC-VAN SCIENCE
NIFTY-Serve PAF01022
CompuServe 74050,1022
**************************************************************/
#include <grub/types.h>
#include <grub/macho.h>
#define N 4096 /* size of ring buffer */
#define F 18 /* upper limit for match_length */
#define THRESHOLD 2 /* encode string into position and length
if match_length is greater than this */
#define NIL N /* index for root of binary search trees */
#define EOF -1
#define getc(file) ((src < srcend) ? *src++ : EOF)
#define putc(c, file) (dst < dstend) ? (*dst++ = (c)) : 0;
grub_size_t
grub_decompress_lzss (grub_uint8_t *dst, grub_uint8_t *dstend,
grub_uint8_t *src, grub_uint8_t *srcend)
{
int i, j, k, r, c;
unsigned int flags;
static unsigned char text_buf[N + F - 1];
grub_uint8_t *dst0 = dst;
for (i = 0; i < N - F; i++) text_buf[i] = ' ';
r = N - F; flags = 0;
for ( ; ; ) {
if (((flags >>= 1) & 256) == 0) {
if ((c = getc(infile)) == EOF) break;
flags = c | 0xff00; /* uses higher byte cleverly */
} /* to count eight */
if (flags & 1) {
if ((c = getc(infile)) == EOF) break;
putc(c, outfile); text_buf[r++] = c; r &= (N - 1);
} else {
if ((i = getc(infile)) == EOF) break;
if ((j = getc(infile)) == EOF) break;
i |= ((j & 0xf0) << 4); j = (j & 0x0f) + THRESHOLD;
for (k = 0; k <= j; k++) {
c = text_buf[(i + k) & (N - 1)];
putc(c, outfile); text_buf[r++] = c; r &= (N - 1);
}
}
}
return dst - dst0;
}
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