#include <u.h>#include <libc.h>#include <draw.h> /* * compressed data are sequences of byte codes.   * if the first byte b has the 0x80 bit set, the next (b^0x80)+1 bytes * are data.  otherwise, it's two bytes specifying a previous string to repeat. */static voidtwiddlecompressed(uchar *buf, int n){	uchar *ebuf;	int j, k, c; 	ebuf = buf+n;	while(buf < ebuf){		c = *buf++;		if(c >= 128){			k = c-128+1;			for(j=0; j<k; j++, buf++)				*buf ^= 0xFF;		}else			buf++;	}} Image *creadimage(Display *d, int fd, int dolock){	char hdr[5*12+1];	Rectangle r;	int m, nb, miny, maxy, new, ldepth;	uchar *buf, *a;	Image *i;	ulong chan; 	if(readn(fd, hdr, 5*12) != 5*12)		return nil; 	/*	 * distinguish new channel descriptor from old ldepth.	 * channel descriptors have letters as well as numbers,	 * while ldepths are a single digit formatted as %-11d.	 */	new = 0;	for(m=0; m<10; m++){		if(hdr[m] != ' '){			new = 1;			break;		}	}	if(hdr[11] != ' '){		werrstr("creadimage: bad format");		return nil;	}	if(new){		hdr[11] = '\0';		if((chan = strtochan(hdr)) == 0){			werrstr("creadimage: bad channel string %s", hdr);			return nil;		}	}else{		ldepth = ((int)hdr[10])-'0';		if(ldepth<0 || ldepth>3){			werrstr("creadimage: bad ldepth %d", ldepth);			return nil;		}		chan = drawld2chan[ldepth];	}	r.min.x=atoi(hdr+1*12);	r.min.y=atoi(hdr+2*12);	r.max.x=atoi(hdr+3*12);	r.max.y=atoi(hdr+4*12);	if(r.min.x>r.max.x || r.min.y>r.max.y){		werrstr("creadimage: bad rectangle");		return nil;	} 	if(dolock)		lockdisplay(d);	i = allocimage(d, r, chan, 0, 0);	if(dolock)		unlockdisplay(d);	if(i == nil)		return nil;	buf = malloc(NCBLOCK);	if(buf == nil)		goto Errout;	miny = r.min.y;	while(miny != r.max.y){		if(readn(fd, hdr, 2*12) != 2*12){		Errout:			if(dolock)				lockdisplay(d);		Erroutlock:			freeimage(i);			if(dolock)				unlockdisplay(d);			free(buf);			return nil;		}		maxy = atoi(hdr+0*12);		nb = atoi(hdr+1*12);		if(maxy<=miny || r.max.y<maxy){			werrstr("creadimage: bad maxy %d", maxy);			goto Errout;		}		if(nb<=0 || NCBLOCK<nb){			werrstr("creadimage: bad count %d", nb);			goto Errout;		}		if(readn(fd, buf, nb)!=nb)			goto Errout;		if(dolock)			lockdisplay(d);		a = bufimage(i->display, 21+nb);		if(a == nil)			goto Erroutlock;		a[0] = 'Y';		BPLONG(a+1, i->id);		BPLONG(a+5, r.min.x);		BPLONG(a+9, miny);		BPLONG(a+13, r.max.x);		BPLONG(a+17, maxy);		if(!new)	/* old image: flip the data bits */			twiddlecompressed(buf, nb);		memmove(a+21, buf, nb);		if(dolock)			unlockdisplay(d);		miny = maxy;	}	free(buf);	return i;}