sys/src/cmd/bzfs/unbflz.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <bio.h>
   4 #include "bzfs.h"
   5
   6 int
   7 Bgetint(Biobuf *b)
   8 {
   9         uchar p[4];
  10
  11         if(Bread(b, p, 4) != 4)
  12                 sysfatal("short read");
  13         return (p[0]<<24)|(p[1]<<16)|(p[2]<<8)|p[3];
  14 }
  15
  16 /*
  17  * memmove but make sure overlap works properly.
  18  */
  19 void
  20 copy(uchar *dst, uchar *src, int n)
  21 {
  22         while(n-- > 0)
  23                 *dst++ = *src++;
  24 }
  25
  26 int
  27 unbflz(int in)
  28 {
  29         int rv, out, p[2];
  30         Biobuf *b, bin;
  31         char buf[5];
  32         uchar *data;
  33         int i, j, length, n, m, o, sum;
  34         ulong *blk;
  35         int nblk, mblk;
  36
  37         if(pipe(p) < 0)
  38                 sysfatal("pipe: %r");
  39
  40         rv = p[0];
  41         out = p[1];
  42         switch(rfork(RFPROC|RFFDG|RFNOTEG|RFMEM)){
  43         case -1:
  44                 sysfatal("fork: %r");
  45         case 0:
  46                 close(rv);
  47                 break;
  48         default:
  49                 close(in);
  50                 close(out);
  51                 return rv;
  52         }
  53
  54         Binit(&bin, in, OREAD);
  55         b = &bin;
  56
  57         if(Bread(b, buf, 4) != 4)
  58                 sysfatal("short read");
  59
  60         if(memcmp(buf, "BLZ\n", 4) != 0)
  61                 sysfatal("bad header");
  62
  63         length = Bgetint(b);
  64         data = malloc(length);
  65         if(data == nil)
  66                 sysfatal("out of memory");
  67         sum = 0;
  68         nblk = 0;
  69         mblk = 0;
  70         blk = nil;
  71         while(sum < length){
  72                 if(nblk>=mblk){
  73                         mblk += 16384;
  74                         blk = realloc(blk, (mblk+1)*sizeof(blk[0]));
  75                         if(blk == nil)
  76                                 sysfatal("out of memory");
  77                 }
  78                 n = Bgetint(b);
  79                 blk[nblk++] = n;
  80                 if(n&(1<<31))
  81                         n &= ~(1<<31);
  82                 else
  83                         blk[nblk++] = Bgetint(b);
  84                 sum += n;
  85         }
  86         if(sum != length)
  87                 sysfatal("bad compressed data %d %d", sum, length);
  88         i = 0;
  89         j = 0;
  90         while(i < length){
  91                 assert(j < nblk);
  92                 n = blk[j++];
  93                 if(n&(1<<31)){
  94                         n &= ~(1<<31);
  95                         if((m=Bread(b, data+i, n)) != n)
  96                                 sysfatal("short read %d %d", n, m);
  97                 }else{
  98                         o = blk[j++];
  99                         copy(data+i, data+o, n);
 100                 }
 101                 i += n;
 102         }
 103         write(out, data, length);
 104         close(in);
 105         close(out);
 106         _exits(0);
 107         return -1;
 108 }