removes escape sequences

unesc.c

#include <u.h>
#include <libc.h>
#include <bio.h>

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

enum {
	ESC = 0x1b,
};

static int
skipnum(Biobuf *rbuf)
{
	int c;

	while((c=Bgetc(rbuf)) != Beof && isdigit(c))
		;
	return c;
}

static void
skipcsi(Biobuf *rbuf)
{
	/* CSI */
	if(skipnum(rbuf) == ';')
		skipnum(rbuf);
}

static void
skipstr(Biobuf *rbuf)
{
	int c;

	while((c=Bgetc(rbuf)) != Beof)
		if(c == ESC && (c=Bgetc(rbuf)) == '\\')
			break;
}

static void
skiposc(Biobuf *rbuf)
{
	/* OSC Ps;Pt ST */
	skipnum(rbuf);
	skipstr(rbuf);
}

static void
unesc(int fd)
{
	Biobuf rbuf, wbuf;
	int c;

	Binit(&rbuf, fd, OREAD);
	Binit(&wbuf, 1, OWRITE);
	while((c=Bgetc(&rbuf)) != Beof){
		if(c != ESC){
			Bputc(&wbuf, c);
			continue;
		}
		c = Bgetc(&rbuf);
		switch(c){
		case Beof:
			fprint(2, "warning: EOF following ESC\n");
			break;
		case 'N':
		case 'O':
		case 'X':
		case 'c':
			// skip one char
			break;
		case 'P':
			// DCS
			break;
		case '[': // CSI
			skipcsi(&rbuf);
			break;
		case ']': // OSC
			skiposc(&rbuf);
			break;
		case '^':
			// PM
			break;
		case '_':
			// APC
			break;
		}
	}
	Bflush(&wbuf);
	Bterm(&rbuf);
	Bterm(&wbuf);
}

void
main(int argc, char **argv)
{
	int i, fd;

	ARGBEGIN {
	default:
		usage();
	} ARGEND
	if(argc == 0)
		unesc(0);
	else
		for(i = 0; i < argc; i++){
			fd = open(argv[i], OREAD);
			if(fd < 0)
				sysfatal("can't open: %r");
			unesc(fd);
			close(fd);
		}
	exits(nil);
}