1  /* Detecting file changes using modification times.
       2     Copyright (C) 2017-2023 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  #include <file_change_detection.h>
      20  
      21  #include <errno.h>
      22  #include <stddef.h>
      23  
      24  bool
      25  __file_is_unchanged (const struct file_change_detection *left,
      26                       const struct file_change_detection *right)
      27  {
      28    if (left->size < 0 || right->size < 0)
      29      /* Negative sizes are used as markers and never match.  */
      30      return false;
      31    else if (left->size == 0 && right->size == 0)
      32      /* Both files are empty or do not exist, so they have the same
      33         content, no matter what the other fields indicate.  */
      34      return true;
      35    else
      36      return left->size == right->size
      37        && left->ino == right->ino
      38        && left->mtime.tv_sec == right->mtime.tv_sec
      39        && left->mtime.tv_nsec == right->mtime.tv_nsec
      40        && left->ctime.tv_sec == right->ctime.tv_sec
      41        && left->ctime.tv_nsec == right->ctime.tv_nsec;
      42  }
      43  libc_hidden_def (__file_is_unchanged)
      44  
      45  void
      46  __file_change_detection_for_stat (struct file_change_detection *file,
      47                                    const struct __stat64_t64 *st)
      48  {
      49    if (S_ISDIR (st->st_mode))
      50      /* Treat as empty file.  */
      51      file->size = 0;
      52    else if (!S_ISREG (st->st_mode))
      53      /* Non-regular files cannot be cached.  */
      54      file->size = -1;
      55    else
      56      {
      57        file->size = st->st_size;
      58        file->ino = st->st_ino;
      59        file->mtime = (struct __timespec64) { st->st_mtim.tv_sec,
      60  					    st->st_mtim.tv_nsec };
      61        file->ctime = (struct __timespec64) { st->st_ctim.tv_sec,
      62  					    st->st_ctim.tv_nsec };
      63      }
      64  }
      65  libc_hidden_def (__file_change_detection_for_stat)
      66  
      67  bool
      68  __file_change_detection_for_path (struct file_change_detection *file,
      69                                    const char *path)
      70  {
      71    struct __stat64_t64 st;
      72    if (__stat64_time64 (path, &st) != 0)
      73      switch (errno)
      74        {
      75        case EACCES:
      76        case EISDIR:
      77        case ELOOP:
      78        case ENOENT:
      79        case ENOTDIR:
      80        case EPERM:
      81          /* Ignore errors due to file system contents.  Instead, treat
      82             the file as empty.  */
      83          file->size = 0;
      84          return true;
      85        default:
      86          /* Other errors are fatal.  */
      87          return false;
      88        }
      89    else /* stat64 was successful.  */
      90      {
      91        __file_change_detection_for_stat (file, &st);
      92        return true;
      93      }
      94  }
      95  libc_hidden_def (__file_change_detection_for_path)
      96  
      97  bool
      98  __file_change_detection_for_fp (struct file_change_detection *file,
      99                                  FILE *fp)
     100  {
     101    if (fp == NULL)
     102      {
     103        /* The file does not exist.  */
     104        file->size = 0;
     105        return true;
     106      }
     107    else
     108      {
     109        struct __stat64_t64 st;
     110        if (__fstat64_time64 (__fileno (fp), &st) != 0)
     111          /* If we already have a file descriptor, all errors are fatal.  */
     112          return false;
     113        else
     114          {
     115            __file_change_detection_for_stat (file, &st);
     116            return true;
     117          }
     118      }
     119  }
     120  libc_hidden_def (__file_change_detection_for_fp)