1 #include <u.h>
2 #include <libc.h>
3
4 /*
5 * In place, rewrite name to compress multiple /, eliminate ., and process ..
6 */
7 #define SEP(x) ((x)=='/' || (x) == 0)
8 char*
cleanname(char * name)9 cleanname(char *name)
10 {
11 char *p, *q, *dotdot;
12 int rooted;
13
14 rooted = name[0] == '/';
15
16 /*
17 * invariants:
18 * p points at beginning of path element we're considering.
19 * q points just past the last path element we wrote (no slash).
20 * dotdot points just past the point where .. cannot backtrack
21 * any further (no slash).
22 */
23 p = q = dotdot = name+rooted;
24 while(*p) {
25 if(p[0] == '/') /* null element */
26 p++;
27 else if(p[0] == '.' && SEP(p[1]))
28 p += 1; /* don't count the separator in case it is nul */
29 else if(p[0] == '.' && p[1] == '.' && SEP(p[2])) {
30 p += 2;
31 if(q > dotdot) { /* can backtrack */
32 while(--q > dotdot && *q != '/')
33 ;
34 } else if(!rooted) { /* /.. is / but ./../ is .. */
35 if(q != name)
36 *q++ = '/';
37 *q++ = '.';
38 *q++ = '.';
39 dotdot = q;
40 }
41 } else { /* real path element */
42 if(q != name+rooted)
43 *q++ = '/';
44 while((*q = *p) != '/' && *q != 0)
45 p++, q++;
46 }
47 }
48 if(q == name) /* empty string is really ``.'' */
49 *q++ = '.';
50 *q = '\0';
51 return name;
52 }
53