#include <u.h>
#include <libc.h>
#include <bio.h>
int
nibble(int c){
	if(c >= '0' && c <= '9')
		return c - '0';
	if(c >= 'a' && c <= 'f')
		return c + 10 - 'a';
	if(c >= 'A' && c <= 'F')
		return c + 10 - 'A';
	return -1;
}
void
main(int argc, char **argv){
	Biobuf *in, *out;
	int c, line;
	char *file;
	switch(argc){
	default:
		sysfatal("usage: %s [file]", argv[0]);
	case 1:
		file = "<stdin>";
		in = Bfdopen(0, OREAD);
		break;
	case 2:
		file = argv[1];
		in = Bopen(file, OREAD);
		break;
	}
	out = Bfdopen(1, OWRITE);
	if(in == nil || out == nil)
		sysfatal("Bopen: %r");
	line = 1;
	while(9){
		c = Bgetc(in);
		if(c == ' ' || c == '\t')
			continue;
		if(c == '#')
			do c = Bgetc(in);
				while(c >= 0 && c != '\n');
		if(c == '\n'){
			line++;
			continue;
		}
		if(c < 0){
			Bterm(in);
			Bterm(out);
			exits(nil);
		}
		c = nibble(c) << 4 | nibble(Bgetc(in));
		if(c < 0)
			sysfatal("bad input: %s:%d", file, line);
		Bputc(out, c);
	}
}