#include <u.h>#include <libc.h>#include <libg.h> #define	CHUNK	6000 Bitmap*rdbitmapfile(int fd){	char hdr[5*12+1];	long dy, px;	ulong l, t, n;	long miny, maxy;	Rectangle r;	int ld;	Bitmap *b; 	if(readn(fd, hdr, 5*12)!=5*12)		berror("rdbitmapfile read");	ld = atoi(hdr+0*12);	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(ld<0 || ld>3)		berror("rdbitmapfile ldepth");	if(r.min.x>r.max.x || r.min.y>r.max.y)		berror("rdbitmapfile rectangle"); 	miny = r.min.y;	maxy = r.max.y;	px = 1<<(3-ld);	/* pixels per byte */	/* set l to number of bytes of data per scan line */	if(r.min.x >= 0)		l = (r.max.x+px-1)/px - r.min.x/px;	else{	/* make positive before divide */		t = (-r.min.x)+px-1;		t = (t/px)*px;		l = (t+r.max.x+px-1)/px;	}	b = balloc(r, ld);	if(b == 0)		return 0;	while(maxy > miny){		dy = maxy - miny;		if(dy*l > CHUNK)			dy = CHUNK/l;		n = dy*l;		if(readn(fd, _btmp, n) != n){			bfree(b);			berror("rdbitmapfile read");		}		wrbitmap(b, miny, miny+dy, _btmp);		miny += dy;	}	return b;}