/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include	<u.h>#include	<libc.h>#include	<bio.h>#include	"sky.h" static	void	dodecode(Biobuf*, Pix*, int, int, uchar*);static	long	getlong(uchar*);int	debug; Img*dssread(char *file){	int nx, ny, scale, sumall;	Pix  *p, *pend;	uchar buf[21];	Biobuf *bp;	Img *ip; 	if(debug)		Bprint(&bout, "reading %s\n", file);	bp = Bopen(file, OREAD);	if(bp == 0)		return 0;	if(Bread(bp, buf, sizeof(buf)) != sizeof(buf) ||	   buf[0] != 0xdd || buf[1] != 0x99){		werrstr("bad format");		return 0;	}	nx = getlong(buf+2);	ny = getlong(buf+6);	scale = getlong(buf+10);	sumall = getlong(buf+14);	if(debug)		fprint(2, "%s: nx=%d, ny=%d, scale=%d, sumall=%d, nbitplanes=%d,%d,%d\n",			file, nx, ny, scale, sumall, buf[18], buf[19], buf[20]);	ip = malloc(sizeof(Img) + (nx*ny-1)*sizeof(int));	if(ip == 0){		Bterm(bp);		werrstr("no memory");		return 0;	}	ip->nx = nx;	ip->ny = ny;	dodecode(bp, ip->a, nx, ny, buf+18);	ip->a[0] = sumall;	/* sum of all pixels */	Bterm(bp);	if(scale > 1){		p = ip->a;		pend = &ip->a[nx*ny];		while(p < pend)			*p++ *= scale;	}	hinv(ip->a, nx, ny);	return ip;} staticvoiddodecode(Biobuf *infile, Pix  *a, int nx, int ny, uchar *nbitplanes){	int nel, nx2, ny2, bits, mask;	Pix *aend, px; 	nel = nx*ny;	nx2 = (nx+1)/2;	ny2 = (ny+1)/2;	memset(a, 0, nel*sizeof(*a)); 	/*	 * Initialize bit input	 */	start_inputing_bits(); 	/*	 * read bit planes for each quadrant	 */	qtree_decode(infile, &a[0],          ny, nx2,  ny2,  nbitplanes[0]);	qtree_decode(infile, &a[ny2],        ny, nx2,  ny/2, nbitplanes[1]);	qtree_decode(infile, &a[ny*nx2],     ny, nx/2, ny2,  nbitplanes[1]);	qtree_decode(infile, &a[ny*nx2+ny2], ny, nx/2, ny/2, nbitplanes[2]); 	/*	 * make sure there is an EOF symbol (nybble=0) at end	 */	if(input_nybble(infile) != 0){		fprint(2, "dodecode: bad bit plane values\n");		exits("format");	} 	/*	 * get the sign bits	 */	aend = &a[nel];	mask = 0;	bits = 0;;	for(; a<aend; a++) {		if(px = *a) {			if(mask == 0) {				mask = 0x80;				bits = Bgetc(infile);			}			if(mask & bits)				*a = -px;			mask >>= 1;		}	}} staticlong	getlong(uchar *p){	return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];}