/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2021 OmniOS Community Edition (OmniOSce) Association.
 */

/*
 * getcwd() returns the pathname of the current working directory.
 * On error, a NULL pointer is returned and errno is set.
 */

#pragma weak _getcwd = getcwd

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

char *
getcwd(char *pathname, size_t size)
{
        int alloc = 0;

        if (size == 0 && pathname == NULL) {
                /*
                 * If no size was provided, start with a buffer that should
                 * accommodate any normal path and, if it is not big enough,
                 * keep doubling it to try and make enough space.
                 *
                 * Any non-global zone path is longer when observed from the
                 * global zone, and some filesystems, including ZFS, support
                 * paths much longer than MAXPATHLEN/_PC_PATH_MAX.
                 *
                 * To protect against unbounded memory usage, cap to 128KiB.
                 * This is an arbitrary limit which is far bigger than the
                 * length of any practical path on the system.
                 */
                if ((size = pathconf(".", _PC_PATH_MAX)) == -1)
                        size = MAXPATHLEN;

                while (size <= 0x20000) {
                        if ((pathname = reallocf(pathname, size)) == NULL) {
                                errno = ENOMEM;
                                return (NULL);
                        }
                        if (syscall(SYS_getcwd, pathname, size) == 0) {
                                char *ret;

                                /*
                                 * Shrink the buffer to the length actually
                                 * required to hold the final path.
                                 */
                                ret = realloc(pathname, strlen(pathname) + 1);
                                if (ret == NULL)
                                        return (pathname);

                                return (ret);
                        }
                        if (errno != ERANGE)
                                break;
                        size <<= 1;
                }
                free(pathname);
                return (NULL);
        }

        if (size == 0) {
                errno = EINVAL;
                return (NULL);
        }

        if (pathname == NULL)  {
                if ((pathname = malloc(size)) == NULL) {
                        errno = ENOMEM;
                        return (NULL);
                }
                alloc = 1;
        }

        if (syscall(SYS_getcwd, pathname, size) == 0)
                return (pathname);

        if (alloc)
                free(pathname);

        return (NULL);
}