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