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#include <u.h>
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#include <libc.h>
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#include <bio.h>
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void
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usage(void)
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{
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	fprint(2, "usage: unbflz [file]\n");
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	exits("usage");
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}
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int
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Bgetint(Biobuf *b)
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{
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	uchar p[4];
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	if(Bread(b, p, 4) != 4)
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		sysfatal("short read");
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	return (p[0]<<24)|(p[1]<<16)|(p[2]<<8)|p[3];
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}
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/*
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 * memmove but make sure overlap works properly.
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 */
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void
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copy(uchar *dst, uchar *src, int n)
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{
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	while(n-- > 0)
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		*dst++ = *src++;
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}
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void
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main(int argc, char **argv)
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{
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	Biobuf *b, bin;
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	char buf[5];
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	uchar *data;
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	ulong *blk, l;
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	int nblk, mblk;
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	int sum;
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	int i, j, length, m, n, o;
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	ARGBEGIN{
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	default:
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		usage();
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	}ARGEND
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	switch(argc){
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	default:
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		usage();
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	case 0:
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		Binit(&bin, 0, OREAD);
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		b = &bin;
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		break;
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	case 1:
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		if((b = Bopen(argv[0], OREAD)) == nil)
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			sysfatal("open %s: %r", argv[0]);
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		break;
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	}
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	if(Bread(b, buf, 4) != 4)
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		sysfatal("short read");
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	if(memcmp(buf, "BLZ\n", 4) != 0)
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		sysfatal("bad header");
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	length = Bgetint(b);
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	data = malloc(length);
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	if(data == nil)
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		sysfatal("out of memory");
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	sum = 0;
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	nblk = 0;
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	mblk = 0;
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	blk = nil;
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	while(sum < length){
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		if(nblk>=mblk){
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			mblk += 16384;
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			blk = realloc(blk, (mblk+1)*sizeof(blk[0]));
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			if(blk == nil)
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				sysfatal("out of memory");
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		}
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		l = Bgetint(b);
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		blk[nblk++] = l;
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		if(l&(1<<31))
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			l &= ~(1<<31);
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		else
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			blk[nblk++] = Bgetint(b);
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		sum += l;
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	}
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	if(sum != length)
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		sysfatal("bad compressed data %d %d", sum, length);
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	i = 0;
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	j = 0;
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	while(i < length){
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		assert(j < nblk);
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		n = blk[j++];
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		if(n&(1<<31)){
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			n &= ~(1<<31);
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			if((m=Bread(b, data+i, n)) != n)
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				sysfatal("short read %d %d", n, m);
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		}else{
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			o = blk[j++];
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			copy(data+i, data+o, n);
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		}
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		i += n;
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	}
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	write(1, data, length);
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	exits(nil);
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}