implement Riff; include "sys.m"; sys: Sys; include "riff.m"; init(){	sys = load Sys Sys->PATH;} open(file: string): (ref RD, string){	fd := sys->open(file, sys->OREAD);	if(fd == nil)		return (nil, "open failed"); 	r := ref RD;	r.fd = fd;	r.buf = array[DEFBUF] of byte;	r.ptr = 0;	r.nbyte = 0; 	(hdr, l) := r.gethdr();	if(hdr != "RIFF")		return (nil, "not a RIFF file"); 	return (r, nil);} RD.gethdr(r: self ref RD): (string, int){	b := array[8] of byte; 	if(r.readn(b, 8) != 8)		return (nil, -1); 	return (string b[0:4], ledword(b, 4));} RD.check4(r: self ref RD, code: string): string{	b := array[4] of byte; 	if(r.readn(b, 4) != 4)		return "file i/o error";	if(string b != code)		return "bad four code header information";	return nil;} RD.avihdr(r: self ref RD): (ref AVIhdr, string){	(s, l) := r.gethdr();	if(s == nil || s != "avih")		return (nil, "missing/malformed avih"); 	b := array[AVImainhdr] of byte;	if(r.readn(b, AVImainhdr) != AVImainhdr)		return (nil, "short read in avih"); 	h := ref AVIhdr; 	h.usecperframe = ledword(b, 0);	h.bytesec = ledword(b, 4);	h.flag = ledword(b, 12);	h.frames = ledword(b, 16);	h.initframes = ledword(b, 20);	h.streams = ledword(b, 24);	h.bufsize = ledword(b, 28);	h.width = ledword(b, 32);	h.height = ledword(b, 36); 	return (h, nil);} RD.streaminfo(r: self ref RD): (ref AVIstream, string){	(h, l) := r.gethdr();	if(h != "LIST")		return (nil, "streaminfo expected LIST"); 	err := r.check4("strl");	if(err != nil)		return (nil, err); 	(strh, sl) := r.gethdr();	if(strh != "strh")		return (nil, "streaminfo expected strh"); 	b := array[sl] of byte;	if(r.readn(b, sl) != sl)		return (nil, "streaminfo strl short read"); 	s := ref AVIstream; 	s.stype = string b[0:4];	s.handler = string b[4:8];	s.flags = ledword(b, 8);	s.priority = ledword(b, 12);	s.initframes = ledword(b, 16);	s.scale = ledword(b, 20);	s.rate = ledword(b, 24);	s.start = ledword(b, 28);	s.length = ledword(b, 32);	s.bufsize = ledword(b, 36);	s.quality = ledword(b, 40);	s.samplesz = ledword(b, 44); 	(strf, sf) := r.gethdr();	if(strf != "strf")		return (nil, "streaminfo expected strf"); 	s.fmt = array[sf] of byte;	if(r.readn(s.fmt, sf) != sf)		return (nil, "streaminfo strf short read"); 	return (s, nil);} RD.readn(r: self ref RD, b: array of byte, l: int): int{	if(r.nbyte < l) {		c := 0;		if(r.nbyte != 0) {			b[0:] = r.buf[r.ptr:];			l -= r.nbyte;			c += r.nbyte;			b = b[r.nbyte:];		}		bsize := len r.buf;		while(l != 0) {			r.nbyte = sys->read(r.fd, r.buf, bsize);			if(r.nbyte <= 0) {				r.nbyte = 0;				return -1;			}			n := l;			if(n > bsize)				n = bsize; 			r.ptr = 0;			b[0:] = r.buf[0:n];			b = b[n:];			r.nbyte -= n;			r.ptr += n;			l -= n;			c += n;		}		return c;	}	b[0:] = r.buf[r.ptr:r.ptr+l];	r.nbyte -= l;	r.ptr += l;	return l;} RD.skip(r: self ref RD, size: int): int{	if(r.nbyte != 0) {		n := size;		if(n > r.nbyte)			n = r.nbyte;		r.ptr += n;		r.nbyte -= n;		size -= n;		if(size == 0)			return 0;	}	return int sys->seek(r.fd, big size, sys->SEEKRELA);} AVIstream.fmt2binfo(a: self ref AVIstream): string{	if(len a.fmt < Binfosize)		return "format is wrong size for BITMAPINFO"; 	b := ref Bitmapinfo; 	# Pull out the bitmap info	b.width = ledword(a.fmt, 4);	b.height = ledword(a.fmt, 8);	b.planes = leword(a.fmt, 12);	b.bitcount = leword(a.fmt, 14);	b.compression = ledword(a.fmt, 16);	b.sizeimage = ledword(a.fmt, 20);	b.xpelpermeter = ledword(a.fmt, 24);	b.ypelpermeter = ledword(a.fmt, 28);	b.clrused = ledword(a.fmt, 32);	b.clrimportant = ledword(a.fmt, 36); 	# Parse out the color map	ncolor := len a.fmt - Binfosize;	if(ncolor & 3)		return "wrong size color map";	ncolor /= 4; 	b.cmap = array[ncolor] of RGB;	idx := 40;	for(i := 0; i < ncolor; i++) {		b.cmap[i].r = int a.fmt[idx+2];		b.cmap[i].g = int a.fmt[idx+1];		b.cmap[i].b = int a.fmt[idx+0];		idx += 4;	} 	a.fmt = nil;	a.binfo = b;	return nil;} leword(b: array of byte, o: int): int{	return 	(int b[o+1] << 8) | int b[o];} ledword(b: array of byte, o: int): int{	return	(int b[o+3] << 24) |		(int b[o+2] << 16) |		(int b[o+1] << 8) |		int b[o];}