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, 2009-2024 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 #include "dirent--.h"
  30 #ifndef _D_EXACT_NAMLEN
  31 # define _D_EXACT_NAMLEN(dp)    strlen ((dp)->d_name)
  32 #endif
  33
  34 #include <stddef.h>
  35 #include <stdlib.h>
  36 #include <string.h>
  37
  38 #include "attribute.h"
  39 #include "xalloc.h"
  40
  41 /* Pacify GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113963>.  */
  42 #if 13 <= __GNUC__
  43 # pragma GCC diagnostic ignored "-Wanalyzer-malloc-leak"
  44 # pragma GCC diagnostic ignored "-Wanalyzer-null-dereference"
  45 #endif
  46
  47 typedef struct
  48 {
  49   /* Offset of file name in name_space.  */
  50   idx_t name;
  51
  52 #if D_INO_IN_DIRENT
  53   /* File inode number.  */
  54   ino_t ino;
  55 #endif
  56 } direntry_t;
  57
  58 /* Compare the names of two directory entries */
  59
  60 static int
  61 direntry_cmp_name (void const *a, void const *b, void *arg)
  62 {
  63   direntry_t const *dea = a;
  64   direntry_t const *deb = b;
  65   char const *name_space = arg;
  66
  67   return strcmp (name_space + dea->name, name_space + deb->name);
  68 }
  69
  70 #if D_INO_IN_DIRENT
  71 /* Compare the inode numbers of two directory entries */
  72
  73 static int
  74 direntry_cmp_inode (void const *a, void const *b, MAYBE_UNUSED void *arg)
  75 {
  76   direntry_t const *dea = a;
  77   direntry_t const *deb = b;
  78
  79   return _GL_CMP (dea->ino, deb->ino);
  80 }
  81 #endif
  82
  83 typedef int (*comparison_function) (void const *, void const *, void *);
  84
  85 static comparison_function const comparison_function_table[] =
  86   {
  87     0,
  88     direntry_cmp_name
  89 #if D_INO_IN_DIRENT
  90     , direntry_cmp_inode
  91 #endif
  92   };
  93
  94 /* Return a freshly allocated string containing the file names
  95    in directory DIRP, separated by '\0' characters;
  96    the end is marked by two '\0' characters in a row.
  97    Returned values are sorted according to OPTION.
  98    Return NULL (setting errno) if DIRP cannot be read.
  99    If DIRP is NULL, return NULL without affecting errno.  */
 100
 101 char *
 102 streamsavedir (DIR *dirp, enum savedir_option option)
 103 {
 104   char *name_space = NULL;
 105   idx_t allocated = 0;
 106   direntry_t *entries = NULL;
 107   idx_t entries_allocated = 0;
 108   idx_t entries_used = 0;
 109   idx_t used = 0;
 110   comparison_function cmp = comparison_function_table[option];
 111
 112   if (dirp == NULL)
 113     return NULL;
 114
 115   for (;;)
 116     {
 117       struct dirent const *dp;
 118       char const *entry;
 119
 120       errno = 0;
 121       dp = readdir (dirp);
 122       if (! dp)
 123         break;
 124
 125       /* Skip "", ".", and "..".  "" is returned by at least one buggy
 126          implementation: Solaris 2.4 readdir on NFS file systems.  */
 127       entry = dp->d_name;
 128       if (entry[entry[0] != '.' ? 0 : entry[1] != '.' ? 1 : 2] != '\0')
 129         {
 130           idx_t entry_size = _D_EXACT_NAMLEN (dp) + 1;
 131           if (allocated - used <= entry_size)
 132             name_space = xpalloc (name_space, &allocated,
 133                                   entry_size - (allocated - used),
 134                                   IDX_MAX - 1, sizeof *name_space);
 135           memcpy (name_space + used, entry, entry_size);
 136           if (cmp)
 137             {
 138               if (entries_allocated == entries_used)
 139                 entries = xpalloc (entries, &entries_allocated, 1, -1,
 140                                    sizeof *entries);
 141               entries[entries_used].name = used;
 142 #if D_INO_IN_DIRENT
 143               entries[entries_used].ino = dp->d_ino;
 144 #endif
 145               entries_used++;
 146             }
 147           used += entry_size;
 148         }
 149     }
 150
 151   if (errno != 0)
 152     {
 153       free (name_space);
 154       name_space = NULL;
 155     }
 156   else if (cmp)
 157     {
 158       if (entries_used)
 159         qsort_r (entries, entries_used, sizeof *entries, cmp, name_space);
 160       char *sorted_name_space = ximalloc (used + 1);
 161       char *p = sorted_name_space;
 162       for (idx_t i = 0; i < entries_used; i++)
 163         p = stpcpy (p, name_space + entries[i].name) + 1;
 164       *p = '\0';
 165       free (name_space);
 166       name_space = sorted_name_space;
 167     }
 168   else
 169     {
 170       if (used == allocated)
 171         name_space = xirealloc (name_space, used + 1);
 172       name_space[used] = '\0';
 173     }
 174
 175   free (entries);
 176   return name_space;
 177 }
 178
 179 /* Return a freshly allocated string containing the file names
 180    in directory DIR, separated by '\0' characters;
 181    the end is marked by two '\0' characters in a row.
 182    Return NULL (setting errno) if DIR cannot be opened, read, or closed.  */
 183
 184 char *
 185 savedir (char const *dir, enum savedir_option option)
 186 {
 187   DIR *dirp = opendir (dir);
 188   if (! dirp)
 189     return NULL;
 190   else
 191     {
 192       char *name_space = streamsavedir (dirp, option);
 193       if (closedir (dirp) != 0)
 194         {
 195           free (name_space);
 196           return NULL;
 197         }
 198       return name_space;
 199     }
 200 }