/*	$NetBSD: scandir.c,v 1.28 2016/12/16 04:45:04 mrg Exp $	*/

/*
 * Copyright (c) 1983, 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.
 * 3. 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 <sys/cdefs.h>

/*
 * Scan the directory dirname calling selectfn to make a list of selected
 * directory entries then sort using qsort and compare routine dcomp.
 * Returns the number of entries and a pointer to a list of pointers to
 * struct dirent (through namelist). Returns -1 if there were any errors.
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <errno.h>
#include <dirent.h>
#include <stdlib.h>
#include <string.h>

#include "dirent_private.h"

/*
 * Compute an estimate of the number of entries in a directory based on
 * the file size. Returns the estimated number of entries or 0 on failure.
 */
static size_t dirsize(int fd, size_t olen) {
  struct stat stb;
  size_t nlen;

  if (fstat(fd, &stb) == -1)
    return 0;
  /*
   * Estimate the array size by taking the size of the directory file
   * and dividing it by a multiple of the minimum size entry.
   */
  nlen = (size_t)(stb.st_size / _DIRENT_MINSIZE((struct dirent *)0));
  /*
   * If the size turns up 0, switch to an alternate strategy and use the
   * file size as the number of entries like ZFS returns. If that turns
   * out to be 0 too return a minimum of 10 entries, plus the old length.
   */
  if (nlen == 0)
    nlen = (size_t)(stb.st_size ? stb.st_size : 10);
  return olen + nlen;
}

#ifndef COMPARARG
#define COMPARARG struct dirent **
#endif

int scandir(const char *dirname, struct dirent ***namelist,
            int (*selectfn)(const struct dirent *),
            int (*dcomp)(const COMPARARG, const COMPARARG)) {
  struct dirent *d, *p, **names, **newnames;
  size_t nitems, arraysz;
  DIR *dirp;

  _DIAGASSERT(dirname != NULL);
  _DIAGASSERT(namelist != NULL);

  if ((dirp = opendir(dirname)) == NULL)
    return -1;

  if ((arraysz = dirsize(dirp->dd_fd, 0)) == 0)
    goto bad;

  names = malloc(arraysz * sizeof(*names));
  if (names == NULL)
    goto bad;

  nitems = 0;
  while ((d = readdir(dirp)) != NULL) {
    if (selectfn != NULL && !(*selectfn)(d))
      continue; /* just selected names */

    /*
     * Check to make sure the array has space left and
     * realloc the maximum size.
     */
    if (nitems >= arraysz) {
      if ((arraysz = dirsize(dirp->dd_fd, arraysz)) == 0)
        goto bad2;
      newnames = realloc(names, arraysz * sizeof(*names));
      if (newnames == NULL)
        goto bad2;
      names = newnames;
    }

    /*
     * Make a minimum size copy of the data
     */
    p = malloc((size_t)_DIRENT_SIZE(d));
    if (p == NULL)
      goto bad2;
    p->d_fileno = d->d_fileno;
    p->d_reclen = d->d_reclen;
    p->d_type = d->d_type;
    p->d_namlen = d->d_namlen;
    (void)memmove(p->d_name, d->d_name, (size_t)(p->d_namlen + 1));
    names[nitems++] = p;
  }
  (void)closedir(dirp);
  if (nitems && dcomp != NULL)
    qsort(names, nitems, sizeof(*names),
          (int (*)(const void *, const void *))dcomp);
  *namelist = names;
  _DIAGASSERT(__type_fit(int, nitems));
  return (int)nitems;

bad2:
  while (nitems-- > 0)
    free(names[nitems]);
  free(names);
bad:
  (void)closedir(dirp);
  return -1;
}
