#include <u.h>
#include <libc.h>
#include "tag.h"

void
usage(void)
{
	fprint(2, "usage: %s type [file]\n", argv0);
	exits("usage");
}

void
main(int argc, char **argv)
{
	char *type;
	int fd;
	vlong offset;
	uchar buf[8192], *p;
	u32int length;

	ARGBEGIN {
	default:
		usage();
	} ARGEND

	if(argc < 1)
		usage();
	type = argv[0];
	argc--; argv++;
	if(strlen(type) != 4)
		sysfatal("invalid type");

	switch(argc) {
	case 0:
		fd = 0;
		break;
	case 1:
		if((fd = open(argv[0], OREAD)) < 0)
			sysfatal("open %s: %r", argv[0]);
		break;
	default:
		usage();
		SET(fd);
	}

	offset = 0;
	while(pread(fd, buf, 8, offset) == 8) {
		p = buf;
		length = g32(&p);
		if(memcmp(type, p, 4) == 0) {
			seek(fd, offset+8, 0);
			dup(fd, 0);
			execl("./8.readn", "readn", smprint("%d", length - 8), nil);
			sysfatal("exec: %r");
		}
		offset += length;
	}

	exits(nil);
}