lib/savedir.c

   1 /* savedir.c -- save the list of files in a directory in a string
   2
   3    Copyright (C) 1990, 1997-2001, 2003-2006, 2009-2025 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation, either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>. */
  20
  21 #include <config.h>
  22
  23 #include "savedir.h"
  24
  25 #include <sys/types.h>
  26
  27 #include <errno.h>
  28
  29 #if GNULIB_DIRENT_SAFER
  30 # include "dirent--.h"
  31 #endif
  32
  33 #ifndef _D_EXACT_NAMLEN
  34 # define _D_EXACT_NAMLEN(dp)    strlen ((dp)->d_name)
  35 #endif
  36
  37 #include <stddef.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40
  41 #include "attribute.h"
  42 #include "xalloc.h"
  43
  44 /* Pacify GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113963>.  */
  45 #if _GL_GNUC_PREREQ (13, 0)
  46 # pragma GCC diagnostic ignored "-Wanalyzer-malloc-leak"
  47 # pragma GCC diagnostic ignored "-Wanalyzer-null-dereference"
  48 #endif
  49
  50 typedef struct
  51 {
  52   /* Offset of file name in name_space.  */
  53   idx_t name;
  54
  55 #if D_INO_IN_DIRENT
  56   /* File inode number.  */
  57   ino_t ino;
  58 #endif
  59 } direntry_t;
  60
  61 /* Compare the names of two directory entries */
  62
  63 static int
  64 direntry_cmp_name (void const *a, void const *b, void *arg)
  65 {
  66   direntry_t const *dea = a;
  67   direntry_t const *deb = b;
  68   char const *name_space = arg;
  69
  70   return strcmp (name_space + dea->name, name_space + deb->name);
  71 }
  72
  73 #if D_INO_IN_DIRENT
  74 /* Compare the inode numbers of two directory entries */
  75
  76 static int
  77 direntry_cmp_inode (void const *a, void const *b, MAYBE_UNUSED void *arg)
  78 {
  79   direntry_t const *dea = a;
  80   direntry_t const *deb = b;
  81
  82   return _GL_CMP (dea->ino, deb->ino);
  83 }
  84 #endif
  85
  86 typedef int (*comparison_function) (void const *, void const *, void *);
  87
  88 static comparison_function const comparison_function_table[] =
  89   {
  90     NULL,
  91     direntry_cmp_name
  92 #if D_INO_IN_DIRENT
  93     , direntry_cmp_inode
  94 #endif
  95   };
  96
  97 /* Return a freshly allocated string containing the file names
  98    in directory DIRP, separated by '\0' characters;
  99    the end is marked by two '\0' characters in a row.
 100    Returned values are sorted according to OPTION.
 101    Return NULL (setting errno) if DIRP cannot be read.
 102    If DIRP is NULL, return NULL without affecting errno.  */
 103
 104 char *
 105 streamsavedir (DIR *dirp, enum savedir_option option)
 106 {
 107   char *name_space = NULL;
 108   idx_t allocated = 0;
 109   direntry_t *entries = NULL;
 110   idx_t entries_allocated = 0;
 111   idx_t entries_used = 0;
 112   idx_t used = 0;
 113   comparison_function cmp = comparison_function_table[option];
 114
 115   if (dirp == NULL)
 116     return NULL;
 117
 118   for (;;)
 119     {
 120       struct dirent const *dp;
 121       char const *entry;
 122
 123       errno = 0;
 124       dp = readdir (dirp);
 125       if (! dp)
 126         {
 127           /* Some readdir()s do not absorb ENOENT (dir deleted but open).
 128              This bug was fixed in glibc 2.3 (2002).  */
 129 #if ! (2 < __GLIBC__ + (3 <= __GLIBC_MINOR__))
 130           if (errno == ENOENT)
 131             errno = 0;
 132 #endif
 133           break;
 134         }
 135
 136       /* Skip "", ".", and "..".  "" is returned by at least one buggy
 137          implementation: Solaris 2.4 readdir on NFS file systems.  */
 138       entry = dp->d_name;
 139       if (entry[entry[0] != '.' ? 0 : entry[1] != '.' ? 1 : 2] != '\0')
 140         {
 141           idx_t entry_size = _D_EXACT_NAMLEN (dp) + 1;
 142           if (allocated - used <= entry_size)
 143             name_space = xpalloc (name_space, &allocated,
 144                                   entry_size - (allocated - used),
 145                                   IDX_MAX - 1, sizeof *name_space);
 146           memcpy (name_space + used, entry, entry_size);
 147           if (cmp)
 148             {
 149               if (entries_allocated == entries_used)
 150                 entries = xpalloc (entries, &entries_allocated, 1, -1,
 151                                    sizeof *entries);
 152               entries[entries_used].name = used;
 153 #if D_INO_IN_DIRENT
 154               entries[entries_used].ino = dp->d_ino;
 155 #endif
 156               entries_used++;
 157             }
 158           used += entry_size;
 159         }
 160     }
 161
 162   if (errno != 0)
 163     {
 164       free (name_space);
 165       name_space = NULL;
 166     }
 167   else if (cmp)
 168     {
 169       if (entries_used)
 170         qsort_r (entries, entries_used, sizeof *entries, cmp, name_space);
 171       char *sorted_name_space = ximalloc (used + 1);
 172       char *p = sorted_name_space;
 173       for (idx_t i = 0; i < entries_used; i++)
 174         p = stpcpy (p, name_space + entries[i].name) + 1;
 175       *p = '\0';
 176       free (name_space);
 177       name_space = sorted_name_space;
 178     }
 179   else
 180     {
 181       if (used == allocated)
 182         name_space = xirealloc (name_space, used + 1);
 183       name_space[used] = '\0';
 184     }
 185
 186   free (entries);
 187   return name_space;
 188 }
 189
 190 /* Return a freshly allocated string containing the file names
 191    in directory DIR, separated by '\0' characters;
 192    the end is marked by two '\0' characters in a row.
 193    Return NULL (setting errno) if DIR cannot be opened, read, or closed.  */
 194
 195 char *
 196 savedir (char const *dir, enum savedir_option option)
 197 {
 198   DIR *dirp = opendir (dir);
 199   if (! dirp)
 200     return NULL;
 201   else
 202     {
 203       char *name_space = streamsavedir (dirp, option);
 204       if (closedir (dirp) != 0)
 205         {
 206           free (name_space);
 207           return NULL;
 208         }
 209       return name_space;
 210     }
 211 }