/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */

#include "lint.h"
#include <sys/types.h>
#include <dirent.h>
#include <sys/param.h>
#include <limits.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/*
 * Canonicalize the path given in file_name, resolving away all symbolic link
 * components.  Store the result into the buffer named by resolved_name, which
 * must be long enough (PATH_MAX bytes will suffice).  Returns NULL
 * on failure and resolved_name on success.  On failure, to maintain
 * compatibility with the past, the contents of file_name will be copied
 * into resolved_name.
 */
static char *
realpath_impl(const char *file_name, char *resolved_name)
{
        char cwd[PATH_MAX];
        int len;

        if (file_name == NULL) {
                errno = EINVAL;
                return (NULL);
        }

        /*
         * Call resolvepath() to resolve all the symlinks in file_name,
         * eliminate embedded "." components, and collapse embedded ".."
         * components.  We may be left with leading ".." components.
         */
        if ((len = resolvepath(file_name, resolved_name, PATH_MAX)) < 0) {
                (void) strlcpy(resolved_name, file_name, PATH_MAX);
                return (NULL);          /* errno set by resolvepath() */
        }

        if (len >= PATH_MAX)    /* "can't happen" */
                len = PATH_MAX - 1;
        resolved_name[len] = '\0';

        if (*resolved_name == '/')      /* nothing more to do */
                return (resolved_name);

        /*
         * Prepend the current working directory to the relative path.
         * If the relative path is not empty (or "."), collapse all of the
         * resulting embedded ".." components with trailing cwd components.
         * We know that getcwd() returns a path name free of symlinks.
         */
        if (getcwd(cwd, sizeof (cwd)) == NULL) {
                (void) strlcpy(resolved_name, file_name, PATH_MAX);
                return (NULL);          /* errno set by getcwd() */
        }

        if (len != 0 && strcmp(resolved_name, ".") != 0) {
                char *relpath = resolved_name;
                char *endcwd = cwd + strlen(cwd);

                /*
                 * Eliminate ".." components from the relative path
                 * left-to-right, components from cwd right-to-left.
                 */
                relpath[len++] = '/';
                while (len >= 3 && strncmp(relpath, "../", 3) == 0) {
                        relpath += 3;
                        len -= 3;
                        while (*--endcwd != '/')
                                continue;
                }
                if (len == 0) {
                        /* the relative path was all ".." components */
                        *endcwd = '\0';
                } else {
                        /* there are non-null components on both sides */
                        relpath[--len] = '\0';
                        *endcwd++ = '/';
                        if (endcwd + len >= cwd + PATH_MAX) {
                                (void) strlcpy(resolved_name,
                                    file_name, PATH_MAX);
                                errno = ENAMETOOLONG;
                                return (NULL);
                        }
                        (void) strcpy(endcwd, relpath);
                }
        }

        (void) strcpy(resolved_name, cwd);
        return (resolved_name);
}

/*
 * Canonicalize the path given in file_name, resolving away all symbolic link
 * components.  If resolved_name is a null pointer, return a malloc()d
 * buffer containing the result, else store the result into resolved_name
 * and return resolved_name.  Return NULL on failure.
 */
char *
realpath(const char *file_name, char *resolved_name)
{
        char buffer[PATH_MAX];

        if (resolved_name != NULL)
                return (realpath_impl(file_name, resolved_name));

        if (realpath_impl(file_name, buffer) != NULL)
                return (strdup(buffer));

        return (NULL);
}

/*
 * GNU extension.
 */
char *
canonicalize_file_name(const char *path)
{
        return (realpath(path, NULL));
}