sysdeps/unix/sysv/linux/readdir64.c

   1 /* Read a directory.  Linux LFS version.
   2    Copyright (C) 1997-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 /* When _DIRENT_MATCHES_DIRENT64 is defined we can alias 'readdir64' to
  20    'readdir'.  However the function signatures are not equal due
  21    different return types, so we need to suppress {__}readdir so weak
  22    and strong alias do not throw conflicting types errors.  */
  23 #define readdir   __no_readdir_decl
  24 #define __readdir __no___readdir_decl
  25 #include <dirent.h>
  26 #undef __readdir
  27 #undef readdir
  28
  29 /* Read a directory entry from DIRP.  */
  30 struct dirent64 *
  31 __readdir64 (DIR *dirp)
  32 {
  33   struct dirent64 *dp;
  34   int saved_errno = errno;
  35
  36 #if IS_IN (libc)
  37   __libc_lock_lock (dirp->lock);
  38 #endif
  39
  40   if (dirp->offset >= dirp->size)
  41     {
  42       /* We've emptied out our buffer.  Refill it.  */
  43
  44       size_t maxread = dirp->allocation;
  45       ssize_t bytes;
  46
  47       bytes = __getdents64 (dirp->fd, dirp->data, maxread);
  48       if (bytes <= 0)
  49         {
  50           /* Linux may fail with ENOENT on some file systems if the
  51              directory inode is marked as dead (deleted).  POSIX
  52              treats this as a regular end-of-directory condition, so
  53              do not set errno in that case, to indicate success.  */
  54           if (bytes == 0 || errno == ENOENT)
  55             __set_errno (saved_errno);
  56 #if IS_IN (libc)
  57           __libc_lock_unlock (dirp->lock);
  58 #endif
  59           return NULL;
  60         }
  61       dirp->size = (size_t) bytes;
  62
  63       /* Reset the offset into the buffer.  */
  64       dirp->offset = 0;
  65     }
  66
  67   dp = (struct dirent64 *) &dirp->data[dirp->offset];
  68   dirp->offset += dp->d_reclen;
  69   dirp->filepos = dp->d_off;
  70
  71 #if IS_IN (libc)
  72   __libc_lock_unlock (dirp->lock);
  73 #endif
  74
  75   return dp;
  76 }
  77 libc_hidden_def (__readdir64)
  78
  79 #if _DIRENT_MATCHES_DIRENT64
  80 strong_alias (__readdir64, __readdir)
  81 weak_alias (__readdir64, readdir64)
  82 weak_alias (__readdir64, readdir)
  83 #else
  84 /* The compat code expects the 'struct direct' with d_ino being a __ino_t
  85    instead of __ino64_t.  */
  86 # include <shlib-compat.h>
  87 # if IS_IN(rtld)
  88 weak_alias (__readdir64, readdir64)
  89 # else
  90 versioned_symbol (libc, __readdir64, readdir64, GLIBC_2_2);
  91 # endif
  92 # if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
  93 #  include <olddirent.h>
  94
  95 attribute_compat_text_section
  96 struct __old_dirent64 *
  97 __old_readdir64 (DIR *dirp)
  98 {
  99   struct __old_dirent64 *dp;
 100   int saved_errno = errno;
 101
 102 #if IS_IN (libc)
 103   __libc_lock_lock (dirp->lock);
 104 #endif
 105
 106   if (dirp->offset >= dirp->size)
 107     {
 108       /* We've emptied out our buffer.  Refill it.  */
 109
 110       size_t maxread = dirp->allocation;
 111       ssize_t bytes;
 112
 113       bytes = __old_getdents64 (dirp->fd, dirp->data, maxread);
 114       if (bytes <= 0)
 115         {
 116           /* Linux may fail with ENOENT on some file systems if the
 117              directory inode is marked as dead (deleted).  POSIX
 118              treats this as a regular end-of-directory condition, so
 119              do not set errno in that case, to indicate success.  */
 120           if (bytes == 0 || errno == ENOENT)
 121             __set_errno (saved_errno);
 122 #if IS_IN (libc)
 123           __libc_lock_unlock (dirp->lock);
 124 #endif
 125           return NULL;
 126         }
 127       dirp->size = (size_t) bytes;
 128
 129       /* Reset the offset into the buffer.  */
 130       dirp->offset = 0;
 131     }
 132
 133   dp = (struct __old_dirent64 *) &dirp->data[dirp->offset];
 134   dirp->offset += dp->d_reclen;
 135   dirp->filepos = dp->d_off;
 136
 137 #if IS_IN (libc)
 138   __libc_lock_unlock (dirp->lock);
 139 #endif
 140
 141   return dp;
 142 }
 143 libc_hidden_def (__old_readdir64)
 144 compat_symbol (libc, __old_readdir64, readdir64, GLIBC_2_1);
 145 # endif /* SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)  */
 146 #endif /* _DIRENT_MATCHES_DIRENT64  */