lib/same-inode.h

   1 /* Determine whether two stat buffers are known to refer to the same file.
   2
   3    Copyright (C) 2006, 2009-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef SAME_INODE_H
  19 #define SAME_INODE_H 1
  20
  21 /* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE.  */
  22 #if !_GL_CONFIG_H_INCLUDED
  23  #error "Please include config.h first."
  24 #endif
  25
  26 #include <sys/stat.h>
  27
  28 _GL_INLINE_HEADER_BEGIN
  29 #ifndef SAME_INODE_INLINE
  30 # define SAME_INODE_INLINE _GL_INLINE
  31 #endif
  32
  33 #ifdef __cplusplus
  34 extern "C" {
  35 #endif
  36
  37
  38 /* True if A and B point to structs with st_dev and st_ino members
  39    that are known to represent the same file.
  40
  41    Use | and ^ to shorten generated code, and to lessen the
  42    probability of screwups if st_ino is an array.  */
  43
  44 #if defined __VMS && __CRTL_VER < 80200000
  45 # define PSAME_INODE(a, b) (! (((a)->st_dev ^ (b)->st_dev) \
  46                                | ((a)->st_ino[0] ^ (b)->st_ino[0]) \
  47                                | ((a)->st_ino[1] ^ (b)->st_ino[1]) \
  48                                | ((a)->st_ino[2] ^ (b)->st_ino[2])))
  49 #elif defined _WIN32 && ! defined __CYGWIN__
  50   /* Native Windows.  */
  51 # if _GL_WINDOWS_STAT_INODES
  52   /* stat() and fstat() set st_dev and st_ino to 0 if information about
  53      the inode is not available.  */
  54 #  if _GL_WINDOWS_STAT_INODES == 2
  55 #   define PSAME_INODE(a, b) \
  56      (! (! ((a)->st_dev | (a)->st_ino._gl_ino[0] | (a)->st_ino._gl_ino[1]) \
  57          | ((a)->st_dev ^ (b)->st_dev) \
  58          | ((a)->st_ino._gl_ino[0] ^ (b)->st_ino._gl_ino[0]) \
  59          | ((a)->st_ino._gl_ino[1] ^ (b)->st_ino._gl_ino[1])))
  60 #  else
  61 #   define PSAME_INODE(a, b) (! (! ((a)->st_dev | (a)->st_ino) \
  62                                  | ((a)->st_dev ^ (b)->st_dev) \
  63                                  | ((a)->st_ino ^ (b)->st_ino)))
  64 #  endif
  65 # else
  66   /* stat() and fstat() set st_ino to 0 always.  */
  67 #  define PSAME_INODE(a, b) 0
  68 # endif
  69 #else
  70   /* POSIX.  */
  71 # define PSAME_INODE(a, b) (! (((a)->st_dev ^ (b)->st_dev) \
  72                                | ((a)->st_ino ^ (b)->st_ino)))
  73 #endif
  74
  75 /* True if struct objects A and B are known to represent the same file.  */
  76
  77 #define SAME_INODE(a, b) PSAME_INODE (&(a), &(b))
  78
  79 /* True if *A and *B represent the same file.  Unlike PSAME_INODE,
  80    args are evaluated once and must point to struct stat.  */
  81
  82 SAME_INODE_INLINE bool
  83 psame_inode (struct stat const *a, struct stat const *b)
  84 {
  85   return PSAME_INODE (a, b);
  86 }
  87
  88
  89 #ifdef __cplusplus
  90 }
  91 #endif
  92
  93 _GL_INLINE_HEADER_END
  94
  95 #endif