/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * Pathname canonicalization for Unix file systems

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/stat.h>

#include <errno.h>

#include <limits.h>

#include <alloca.h>

/* Note: The comments in this file use the terminology

         defined in the java.io.File class */

/* Check the given name sequence to see if it can be further collapsed.

   Return zero if not, otherwise return the number of names in the sequence. */

static int

collapsible(char *names)

{

    char *p = names;

    int dots = 0, n = 0;

    while (*p) {

        if ((p[0] == '.') && ((p[1] == '\0')

                              || (p[1] == '/')

                              || ((p[1] == '.') && ((p[2] == '\0')

                                                    || (p[2] == '/'))))) {

            dots = 1;

        }

        n++;

        while (*p) {

            if (*p == '/') {

                p++;

                break;

            }

            p++;

        }

    }

    return (dots ? n : 0);

}

/* Split the names in the given name sequence,

   replacing slashes with nulls and filling in the given index array */

static void

splitNames(char *names, char **ix)

{

    char *p = names;

    int i = 0;

    while (*p) {

        ix[i++] = p++;

        while (*p) {

            if (*p == '/') {

                *p++ = '\0';

                break;

            }

            p++;

        }

    }

}

/* Join the names in the given name sequence, ignoring names whose index

   entries have been cleared and replacing nulls with slashes as needed */

static void

joinNames(char *names, int nc, char **ix)

{

    int i;

    char *p;

    for (i = 0, p = names; i < nc; i++) {

        if (!ix[i]) continue;

        if (i > 0) {

            p[-1] = '/';

        }

        if (p == ix[i]) {

            p += strlen(p) + 1;

        } else {

            char *q = ix[i];

            while ((*p++ = *q++));

        }

    }

    *p = '\0';

}

/* Collapse "." and ".." names in the given path wherever possible.

   A "." name may always be eliminated; a ".." name may be eliminated if it

   follows a name that is neither "." nor "..".  This is a syntactic operation

   that performs no filesystem queries, so it should only be used to cleanup

   after invoking the realpath() procedure. */

static void

collapse(char *path)

{

    char *names = (path[0] == '/') ? path + 1 : path; /* Preserve first '/' */

    int nc;

    char **ix;

    int i, j;

    char *p, *q;

    nc = collapsible(names);

    if (nc < 2) return;         /* Nothing to do */

    ix = (char **)alloca(nc * sizeof(char *));

    splitNames(names, ix);

    for (i = 0; i < nc; i++) {

        int dots = 0;

        /* Find next occurrence of "." or ".." */

        do {

            char *p = ix[i];

            if (p[0] == '.') {

                if (p[1] == '\0') {

                    dots = 1;

                    break;

                }

                if ((p[1] == '.') && (p[2] == '\0')) {

                    dots = 2;

                    break;

                }

            }

            i++;

        } while (i < nc);

        if (i >= nc) break;

        /* At this point i is the index of either a "." or a "..", so take the

           appropriate action and then continue the outer loop */

        if (dots == 1) {

            /* Remove this instance of "." */

            ix[i] = 0;

        }

        else {

            /* If there is a preceding name, remove both that name and this

               instance of ".."; otherwise, leave the ".." as is */

            for (j = i - 1; j >= 0; j--) {

                if (ix[j]) break;

            }

            if (j < 0) continue;

            ix[j] = 0;

            ix[i] = 0;

        }

        /* i will be incremented at the top of the loop */

    }

    joinNames(names, nc, ix);

}

/* Convert a pathname to canonical form.  The input path is assumed to contain

   no duplicate slashes.  On Solaris we can use realpath() to do most of the

   work, though once that's done we still must collapse any remaining "." and

   ".." names by hand. */

int

canonicalize(char *original, char *resolved, int len)

{

    if (len < PATH_MAX) {

        errno = EINVAL;

        return -1;

    }

    if (strlen(original) > PATH_MAX) {

        errno = ENAMETOOLONG;

        return -1;

    }

    /* First try realpath() on the entire path */

    if (realpath(original, resolved)) {

        /* That worked, so return it */

        collapse(resolved);

        return 0;

    }

    else {

        /* Something's bogus in the original path, so remove names from the end

           until either some subpath works or we run out of names */

        char *p, *end, *r = NULL;

        char path[PATH_MAX + 1];

        strncpy(path, original, sizeof(path));

        if (path[PATH_MAX] != '\0') {

            errno = ENAMETOOLONG;

            return -1;

        }

        end = path + strlen(path);

        for (p = end; p > path;) {

            /* Skip last element */

            while ((--p > path) && (*p != '/'));

            if (p == path) break;

            /* Try realpath() on this subpath */

            *p = '\0';

            r = realpath(path, resolved);

            *p = (p == end) ? '\0' : '/';

            if (r != NULL) {

                /* The subpath has a canonical path */

                break;

            }

            else if (errno == ENOENT || errno == ENOTDIR || errno == EACCES) {

                /* If the lookup of a particular subpath fails because the file

                   does not exist, because it is of the wrong type, or because

                   access is denied, then remove its last name and try again.

                   Other I/O problems cause an error return. */

                continue;

            }

            else {

                return -1;

            }

        }

        if (r != NULL) {

            /* Append unresolved subpath to resolved subpath */

            int rn = strlen(r);

            if (rn + (int)strlen(p) >= len) {

                /* Buffer overflow */

                errno = ENAMETOOLONG;

                return -1;

            }

            if ((rn > 0) && (r[rn - 1] == '/') && (*p == '/')) {

                /* Avoid duplicate slashes */

                p++;

            }

            strcpy(r + rn, p);

            collapse(r);

            return 0;

        }

        else {

            /* Nothing resolved, so just return the original path */

            strcpy(resolved, path);

            collapse(resolved);

            return 0;

        }

    }

}