Subversion Repositories planix.SVN

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

/*
 * In place, rewrite name to compress multiple /, eliminate ., and process ..
 */
#define SEP(x)  ((x)=='/' || (x) == 0)
char*
cleanname(char *name)
{
        char *p, *q, *dotdot;
        int rooted;

        rooted = name[0] == '/';

        /*
         * invariants:
         *      p points at beginning of path element we're considering.
         *      q points just past the last path element we wrote (no slash).
         *      dotdot points just past the point where .. cannot backtrack
         *              any further (no slash).
         */
        p = q = dotdot = name+rooted;
        while(*p) {
                if(p[0] == '/') /* null element */
                        p++;
                else if(p[0] == '.' && SEP(p[1]))
                        p += 1; /* don't count the separator in case it is nul */
                else if(p[0] == '.' && p[1] == '.' && SEP(p[2])) {
                        p += 2;
                        if(q > dotdot) {        /* can backtrack */
                                while(--q > dotdot && *q != '/')
                                        ;
                        } else if(!rooted) {    /* /.. is / but ./../ is .. */
                                if(q != name)
                                        *q++ = '/';
                                *q++ = '.';
                                *q++ = '.';
                                dotdot = q;
                        }
                } else {        /* real path element */
                        if(q != name+rooted)
                                *q++ = '/';
                        while((*q = *p) != '/' && *q != 0)
                                p++, q++;
                }
        }
        if(q == name)   /* empty string is really ``.'' */
                *q++ = '.';
        *q = '\0';
        return name;
}