ref: 7b58000c3d019d157fa5f1cc5621b0923e5b8539
dir: /libc/cleanname.c/
#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, erasedprefix;
rooted = name[0] == '/';
erasedprefix = 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])) {
if(p == name)
erasedprefix = 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;
}
if(q == name)
erasedprefix = 1; /* erased entire path via dotdot */
} 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';
if(erasedprefix && name[0] == '#'){
/* this was not a #x device path originally - make it not one now */
memmove(name+2, name, strlen(name)+1);
name[0] = '.';
name[1] = '/';
}
return name;
}