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/* resolve.c -- resolve symbolic links in a pathname
Copyright (C) 1995 Bruno Haible
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
TITLE
RESOLVE(3)
SYNOPSIS
char* resolve (const char* path, char resolved_path[PATH_MAX]);
DESCRIPTION
resolve() expands all symbolic links and resolves refer-
ences to '/./', '/../' and extra '/' characters in the null
terminated string named by path and stores the canonicalized
pathname in the buffer named by resolved_path. The resulting
path will have no symbolic links components, nor any '/./'
or '/../' components.
RETURN VALUES
resolve() returns a pointer to the resolved_path on suc-
cess. On failure, it returns NULL, sets errno to indicate
the error, and places in resolved_path the absolute pathname
of the path component which could not be resolved.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <sys/types.h>
#include <errno.h>
#ifndef errno
extern int errno;
#endif
#include <sys/param.h>
#include "system.h"
#ifndef MAXSYMLINKS
#define MAXSYMLINKS 8
#endif
#ifndef ELOOP_VALUE
#define ELOOP_VALUE ELOOP
#endif
#ifdef S_ISLNK
int readlink();
#endif
char* resolve(path,resolved_path)
const char* path;
char* resolved_path;
{
#ifdef S_ISLNK
char mypath[PATH_MAX];
int symlinkcount = 0; /* Anzahl bisher aufgetretener symbolischer Links */
#endif
char* resolved_limit = &resolved_path[PATH_MAX-1];
/* Gltige Pointer sind die mit resolved_path <= ptr <= resolved_limit. */
/* In *resolved_limit darf hchstens noch ein Nullbyte stehen. */
/* (Analog mit mypath.) */
{
char* resolved_ptr = resolved_path; /* (bleibt stets <= resolved_limit) */
/* Dann path selber einkopieren: */
{
const char* path_ptr = path;
while ((resolved_ptr < resolved_limit) && *path_ptr)
{ *resolved_ptr++ = *path_ptr++; }
/* Mit '/' und einem Nullbyte abschlieen: */
if (resolved_ptr < resolved_limit)
{ *resolved_ptr++ = '/'; }
*resolved_ptr = 0;
} }
{
char* from_ptr = &resolved_path[0];
char* to_ptr = &resolved_path[0];
while ((to_ptr < resolved_limit) && (*from_ptr))
/* Bis hierher hat der Pfad in resolved_path[0]...to_ptr[-1] */
/* die Gestalt '[/]subdir1/subdir2/.../txt', */
/* wobei 'txt' evtl. leer, aber kein subdir leer. */
{
char next = *from_ptr++; *to_ptr++ = next;
if ((next == '/') && (to_ptr >= resolved_path+2))
/* to_ptr[-1]='/' -> Directory ...to_ptr[-2] auflsen: */
{
char* last_subdir_end = &to_ptr[-2];
switch (*last_subdir_end)
{
case '/':
/* '//' wird zu '/' vereinfacht: */
to_ptr--;
break;
case '.':
{
char* last_subdir_ptr = &last_subdir_end[-1];
if (to_ptr > resolved_path+2)
{
if (*last_subdir_ptr == '.')
{
if ((to_ptr > resolved_path+4) && (*--last_subdir_ptr == '/'))
/* letztes subdir war '/../' */
/* Dafr das subdir davor entfernen: */
{
while ((last_subdir_ptr > resolved_path) && !(*--last_subdir_ptr == '/')) ;
to_ptr = last_subdir_ptr+1;
} }
else if (*last_subdir_ptr == '/')
{
/* letztes subdir war '/./' */
/* entfernen: */
to_ptr = last_subdir_end;
} } }
break;
default:
/* nach einem normalen subdir */
#ifdef S_ISLNK
/* symbolischen Link lesen: */
to_ptr[-1]=0; /* '/' durch 0 ersetzen */
{
int linklen = readlink(resolved_path,mypath,sizeof(mypath)-1);
if (linklen >=0)
/* war ein symbolisches Link */
{
if (++symlinkcount > MAXSYMLINKS)
{ errno = ELOOP_VALUE; return NULL; }
/* noch aufzulsenden path-Anteil an den Link-Inhalt anhngen: */
{
char* mypath_ptr = &mypath[linklen]; /* ab hier ist Platz */
char* mypath_limit = &mypath[PATH_MAX-1]; /* bis hierher */
if (mypath_ptr < mypath_limit)
{ *mypath_ptr++ = '/'; } /* erst ein '/' anhngen */
/* dann den Rest: */
while ((mypath_ptr <= mypath_limit) && (*mypath_ptr = *from_ptr++))
{ mypath_ptr++; }
*mypath_ptr = 0; /* und mit 0 abschlieen */
}
/* Dies ersetzt bzw. ergnzt den path: */
if (mypath[0] == '/')
/* ersetzt den path: */
{
from_ptr = &mypath[0]; to_ptr = resolved_path;
while ((*to_ptr++ = *from_ptr++)) ;
from_ptr = resolved_path;
}
else
/* ergnzt den path: */
{
/* Linknamen streichen. Dazu bis zum letzten '/' suchen: */
{
char* ptr = &to_ptr[-1];
while ((ptr > resolved_path) && !(ptr[-1] == '/'))
ptr--;
from_ptr = ptr;
}
{
char* mypath_ptr = &mypath[0]; to_ptr = from_ptr;
while ((to_ptr <= resolved_limit) && (*to_ptr++ = *mypath_ptr++));
} }
to_ptr = from_ptr;
}
else
if ((errno == EINVAL)
#if defined(sgi) || defined(__sgi) /* Irix */
|| (errno == ENXIO)
#endif
)
/* kein symbolisches Link */
{ to_ptr[-1] = '/'; } /* wieder den '/' eintragen */
else
{ return NULL; } /* Fehler */
}
#endif
break;
} }
} /* dann zum nchsten subdir */
/* ein '/' am Ende streichen: */
if ((to_ptr[-1] == '/') && (to_ptr > resolved_path+1))
{ to_ptr--; }
to_ptr[0] = 0; /* durch 0 abschlieen */
return resolved_path; /* fertig */
} }
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