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+/* savedir.c -- save the list of files in a directory in a string
+
+ Copyright (C) 1990, 1997-2001, 2003-2006, 2009-2023 Free Software
+ Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by David MacKenzie <djm@gnu.ai.mit.edu>. */
+
+#include <config.h>
+
+#include "savedir.h"
+
+#include <sys/types.h>
+
+#include <errno.h>
+
+#include "dirent--.h"
+#ifndef _D_EXACT_NAMLEN
+# define _D_EXACT_NAMLEN(dp) strlen ((dp)->d_name)
+#endif
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "xalloc.h"
+
+typedef struct
+{
+ char *name;
+#if D_INO_IN_DIRENT
+ ino_t ino;
+#endif
+} direntry_t;
+
+/* Compare the names of two directory entries */
+
+static int
+direntry_cmp_name (void const *a, void const *b)
+{
+ direntry_t const *dea = a;
+ direntry_t const *deb = b;
+
+ return strcmp (dea->name, deb->name);
+}
+
+#if D_INO_IN_DIRENT
+/* Compare the inode numbers of two directory entries */
+
+static int
+direntry_cmp_inode (void const *a, void const *b)
+{
+ direntry_t const *dea = a;
+ direntry_t const *deb = b;
+
+ return _GL_CMP (dea->ino, deb->ino);
+}
+#endif
+
+typedef int (*comparison_function) (void const *, void const *);
+
+static comparison_function const comparison_function_table[] =
+ {
+ 0,
+ direntry_cmp_name
+#if D_INO_IN_DIRENT
+ , direntry_cmp_inode
+#endif
+ };
+
+/* Return a freshly allocated string containing the file names
+ in directory DIRP, separated by '\0' characters;
+ the end is marked by two '\0' characters in a row.
+ Returned values are sorted according to OPTION.
+ Return NULL (setting errno) if DIRP cannot be read.
+ If DIRP is NULL, return NULL without affecting errno. */
+
+char *
+streamsavedir (DIR *dirp, enum savedir_option option)
+{
+ char *name_space = NULL;
+ idx_t allocated = 0;
+ direntry_t *entries = NULL;
+ idx_t entries_allocated = 0;
+ idx_t entries_used = 0;
+ idx_t used = 0;
+ comparison_function cmp = comparison_function_table[option];
+
+ if (dirp == NULL)
+ return NULL;
+
+ for (;;)
+ {
+ struct dirent const *dp;
+ char const *entry;
+
+ errno = 0;
+ dp = readdir (dirp);
+ if (! dp)
+ break;
+
+ /* Skip "", ".", and "..". "" is returned by at least one buggy
+ implementation: Solaris 2.4 readdir on NFS file systems. */
+ entry = dp->d_name;
+ if (entry[entry[0] != '.' ? 0 : entry[1] != '.' ? 1 : 2] != '\0')
+ {
+ idx_t entry_size = _D_EXACT_NAMLEN (dp) + 1;
+ if (cmp)
+ {
+ if (entries_allocated == entries_used)
+ entries = xpalloc (entries, &entries_allocated, 1, -1,
+ sizeof *entries);
+ entries[entries_used].name = xstrdup (entry);
+#if D_INO_IN_DIRENT
+ entries[entries_used].ino = dp->d_ino;
+#endif
+ entries_used++;
+ }
+ else
+ {
+ if (allocated - used <= entry_size)
+ name_space = xpalloc (name_space, &allocated,
+ entry_size - (allocated - used),
+ IDX_MAX - 1, sizeof *name_space);
+ memcpy (name_space + used, entry, entry_size);
+ }
+ used += entry_size;
+ }
+ }
+
+ if (errno != 0)
+ {
+ free (entries);
+ free (name_space);
+ return NULL;
+ }
+
+ if (cmp)
+ {
+ if (entries_used)
+ qsort (entries, entries_used, sizeof *entries, cmp);
+ name_space = ximalloc (used + 1);
+ used = 0;
+ for (idx_t i = 0; i < entries_used; i++)
+ {
+ char *dest = name_space + used;
+ used += stpcpy (dest, entries[i].name) - dest + 1;
+ free (entries[i].name);
+ }
+ free (entries);
+ }
+ else if (used == allocated)
+ name_space = xirealloc (name_space, used + 1);
+
+ name_space[used] = '\0';
+ return name_space;
+}
+
+/* Return a freshly allocated string containing the file names
+ in directory DIR, separated by '\0' characters;
+ the end is marked by two '\0' characters in a row.
+ Return NULL (setting errno) if DIR cannot be opened, read, or closed. */
+
+char *
+savedir (char const *dir, enum savedir_option option)
+{
+ DIR *dirp = opendir (dir);
+ if (! dirp)
+ return NULL;
+ else
+ {
+ char *name_space = streamsavedir (dirp, option);
+ if (closedir (dirp) != 0)
+ {
+ free (name_space);
+ return NULL;
+ }
+ return name_space;
+ }
+}