arch/all-pc/boot/grub2-aros/grub-core/loader/lzss.c

   1 /**************************************************************
   2         LZSS.C -- A Data Compression Program
   3         (tab = 4 spaces)
   4 ***************************************************************
   5         4/6/1989 Haruhiko Okumura
   6         Use, distribute, and modify this program freely.
   7         Please send me your improved versions.
   8                 PC-VAN          SCIENCE
   9                 NIFTY-Serve     PAF01022
  10                 CompuServe      74050,1022
  11 **************************************************************/
  12
  13 #include <grub/types.h>
  14 #include <grub/macho.h>
  15
  16 #define N                4096   /* size of ring buffer */
  17 #define F                  18   /* upper limit for match_length */
  18 #define THRESHOLD       2   /* encode string into position and length
  19                                                    if match_length is greater than this */
  20 #define NIL                     N       /* index for root of binary search trees */
  21
  22 #define EOF -1
  23 #define getc(file) ((src < srcend) ? *src++ : EOF)
  24 #define putc(c, file) (dst < dstend) ? (*dst++ = (c)) : 0;
  25
  26 grub_size_t
  27 grub_decompress_lzss (grub_uint8_t *dst, grub_uint8_t *dstend,
  28                       grub_uint8_t *src, grub_uint8_t *srcend)
  29 {
  30         int  i, j, k, r, c;
  31         unsigned int  flags;
  32         static unsigned char text_buf[N + F - 1];
  33         grub_uint8_t *dst0 = dst;
  34
  35         for (i = 0; i < N - F; i++) text_buf[i] = ' ';
  36         r = N - F;  flags = 0;
  37         for ( ; ; ) {
  38                 if (((flags >>= 1) & 256) == 0) {
  39                         if ((c = getc(infile)) == EOF) break;
  40                         flags = c | 0xff00;             /* uses higher byte cleverly */
  41                 }                                                       /* to count eight */
  42                 if (flags & 1) {
  43                         if ((c = getc(infile)) == EOF) break;
  44                         putc(c, outfile);  text_buf[r++] = c;  r &= (N - 1);
  45                 } else {
  46                         if ((i = getc(infile)) == EOF) break;
  47                         if ((j = getc(infile)) == EOF) break;
  48                         i |= ((j & 0xf0) << 4);  j = (j & 0x0f) + THRESHOLD;
  49                         for (k = 0; k <= j; k++) {
  50                                 c = text_buf[(i + k) & (N - 1)];
  51                                 putc(c, outfile);  text_buf[r++] = c;  r &= (N - 1);
  52                         }
  53                 }
  54         }
  55     return dst - dst0;
  56 }