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WebSVN – planix.SVN – Blame – /os/branches/planix-v0/sys/src/cmd/unix/drawterm/libc/cleanname.c – Rev 2

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#include <u.h>
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#include <libc.h>
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/*
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 * In place, rewrite name to compress multiple /, eliminate ., and process ..
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 */
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#define SEP(x)	((x)=='/' || (x) == 0)
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char*
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cleanname(char *name)
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{
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	char *p, *q, *dotdot;
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	int rooted;
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	rooted = name[0] == '/';
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	/*
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	 * invariants:
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	 *	p points at beginning of path element we're considering.
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	 *	q points just past the last path element we wrote (no slash).
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	 *	dotdot points just past the point where .. cannot backtrack
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	 *		any further (no slash).
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	 */
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	p = q = dotdot = name+rooted;
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	while(*p) {
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		if(p[0] == '/')	/* null element */
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			p++;
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		else if(p[0] == '.' && SEP(p[1]))
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			p += 1;	/* don't count the separator in case it is nul */
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		else if(p[0] == '.' && p[1] == '.' && SEP(p[2])) {
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			p += 2;
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			if(q > dotdot) {	/* can backtrack */
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				while(--q > dotdot && *q != '/')
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					;
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			} else if(!rooted) {	/* /.. is / but ./../ is .. */
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				if(q != name)
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					*q++ = '/';
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				*q++ = '.';
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				*q++ = '.';
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				dotdot = q;
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			}
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		} else {	/* real path element */
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			if(q != name+rooted)
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				*q++ = '/';
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			while((*q = *p) != '/' && *q != 0)
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				p++, q++;
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		}
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	}
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	if(q == name)	/* empty string is really ``.'' */
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		*q++ = '.';
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	*q = '\0';
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	return name;
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}