Subject: Re: User-relative paths

From: "H. Peter Anvin" <[email-masked]>
Date: Sun, 23 Oct 2005 18:44:13 -0700

Linus Torvalds wrote:
> 
> On Sun, 23 Oct 2005, H. Peter Anvin wrote:
> 
>>If this is meant to dequote shell-quoted paths, it really should be modal.
> 
> It _only_ accepts quoted strings, so it "is" modal. It has one mode: 
> string. And it's a bitch about enforcing it, too (it just dies if it 
> wasn't one).
> 

That wasn't what I meant.  '...' is a modal escape in the shell.  Thus, 
something like this which actually mimics the state machine, at least 
for the potential characters we care about.

#define EMIT(x) { ( ++len < n ) && *dst++ = (x) )

int unquote(char *dst, size_t n, const char *src)
{
	enum state st = { st_zero, st_quote, st_escape };
	int len = 0;
	char c;
	
	while ( (c = *src++) ) {
		switch ( st ) {
		case st_zero:
			if ( c == '\'' )
				st = st_quote;
			else if ( c == '\\' )
				st = st_escape;
			else
				EMIT(c);
			break;
			
		case st_quote:
			if ( c == '\'' )
				st = st_zero;
			else
				EMIT(c);
			break;
			
		case st_escape:
			EMIT(c);
			st = st_zero;
			break;
		}
	}
	
	if ( n )
		*dst = 0;
	
	return (st == st_zero) ? len : -1;
}