pgmkdirp.c

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/*
 * This is adapted from FreeBSD's src/bin/mkdir/mkdir.c, which bears
 * the following copyright notice:
 *
 * Copyright (c) 1983, 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#include "c.h"
 
#include <sys/stat.h>
 
 
/*
 * pg_mkdir_p --- create a directory and, if necessary, parent directories
 *
 * This is equivalent to "mkdir -p" except we don't complain if the target
 * directory already exists.
 *
 * We assume the path is in canonical form, i.e., uses / as the separator.
 *
 * omode is the file permissions bits for the target directory.  Note that any
 * parent directories that have to be created get permissions according to the
 * prevailing umask, but with u+wx forced on to ensure we can create there.
 * (We declare omode as int, not mode_t, to minimize dependencies for port.h.)
 *
 * Returns 0 on success, -1 (with errno set) on failure.
 *
 * Note that on failure, the path arg has been modified to show the particular
 * directory level we had problems with.
 */
int
pg_mkdir_p(char *path, int omode)
{
    mode_t      numask,
                oumask;
    int         last,
                retval;
    char       *p;
 
    retval = 0;
    p = path;
 
#ifdef WIN32
    /* skip network and drive specifiers for win32 */
    if (strlen(p) >= 2)
    {
        if (p[0] == '/' && p[1] == '/')
        {
            /* network drive */
            p = strchr(p + 2, '/');
            if (p == NULL)
            {
                errno = EINVAL;
                return -1;
            }
        }
        else if (p[1] == ':' &&
                 ((p[0] >= 'a' && p[0] <= 'z') ||
                  (p[0] >= 'A' && p[0] <= 'Z')))
        {
            /* local drive */
            p += 2;
        }
    }
#endif
 
    /*
     * POSIX 1003.2: For each dir operand that does not name an existing
     * directory, effects equivalent to those caused by the following command
     * shall occur:
     *
     * mkdir -p -m $(umask -S),u+wx $(dirname dir) && mkdir [-m mode] dir
     *
     * We change the user's umask and then restore it, instead of doing
     * chmod's.  Note we assume umask() can't change errno.
     */
    oumask = umask(0);
    numask = oumask & ~(S_IWUSR | S_IXUSR);
    (void) umask(numask);
 
    if (p[0] == '/')            /* Skip leading '/'. */
        ++p;
    for (last = 0; !last; ++p)
    {
        if (p[0] == '\0')
            last = 1;
        else if (p[0] != '/')
            continue;
        *p = '\0';
        if (!last && p[1] == '\0')
            last = 1;
 
        if (last)
            (void) umask(oumask);
 
        if (mkdir(path, last ? omode : S_IRWXU | S_IRWXG | S_IRWXO) < 0)
        {
            /*
             * If we got EEXIST because there's already a directory there,
             * don't complain.
             */
#ifndef WIN32
            int         save_errno = errno;
            struct stat sb;
 
            if (save_errno != EEXIST ||
                stat(path, &sb) != 0 ||
                !S_ISDIR(sb.st_mode))
            {
                /* Don't let stat replace mkdir's errno */
                errno = save_errno;
                retval = -1;
                break;
            }
#else                           /* WIN32 */
            /*
             * On Windows, stat() opens a handle and can transiently fail on a
             * directory another process is concurrently creating.  Probe with
             * a path-based attribute query instead: it requests only
             * FILE_READ_ATTRIBUTES and is exempt from share-mode denial, so
             * it reliably sees a concurrently-created directory.  We assume
             * GetFileAttributes() won't change errno.
             */
            DWORD       attr = GetFileAttributes(path);
 
            if (errno != EEXIST ||
                attr == INVALID_FILE_ATTRIBUTES ||
                !(attr & FILE_ATTRIBUTE_DIRECTORY))
            {
                retval = -1;
                break;
            }
#endif                          /* WIN32 */
        }
 
        if (!last)
            *p = '/';
    }
 
    /* ensure we restored umask */
    (void) umask(oumask);
 
    return retval;
}