tests/test-fpurge.c

   1 /* Test of fpurge() function.
   2    Copyright (C) 2007-2025 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
  18
  19 #include <config.h>
  20
  21 /* None of the files accessed by this test are large, so disable the
  22    fseek link warning if we are not using the gnulib fseek module.  */
  23 #define _GL_NO_LARGE_FILES
  24 #include <stdio.h>
  25
  26 #include <string.h>
  27
  28 #include "macros.h"
  29
  30 #define TESTFILE "t-fpurge.tmp"
  31
  32 int
  33 main (void)
  34 {
  35   int check_filepos;
  36
  37   for (check_filepos = 0; check_filepos <= 1; check_filepos++)
  38     {
  39       FILE *fp;
  40
  41       /* Create a file with some contents.  */
  42       fp = fopen (TESTFILE, "w");
  43       if (fp == NULL)
  44         goto skip;
  45       if (fwrite ("foobarsh", 1, 8, fp) < 8)
  46         goto skip;
  47       if (fclose (fp))
  48         goto skip;
  49
  50       /* The file's contents is now "foobarsh".  */
  51
  52       /* Open it in read-write mode.  */
  53       fp = fopen (TESTFILE, "r+");
  54       if (fp == NULL)
  55         goto skip;
  56       if (fseek (fp, 3, SEEK_CUR))
  57         goto skip;
  58       if (fwrite ("g", 1, 1, fp) < 1)
  59         goto skip;
  60       if (fflush (fp))
  61         goto skip;
  62       if (fwrite ("bz", 1, 2, fp) < 2)
  63         goto skip;
  64       /* Discard pending write.  */
  65       ASSERT (fpurge (fp) == 0);
  66       /* Verify that when discarding pending output, the file position is set
  67          back to where it was before the write calls.  */
  68       if (check_filepos)
  69         ASSERT (ftell (fp) == 4);
  70       ASSERT (fclose (fp) == 0);
  71
  72       /* Open it in read-only mode.  */
  73       fp = fopen (TESTFILE, "r");
  74       if (fp == NULL)
  75         goto skip;
  76       /* Verify that the pending writes before the fpurge were really
  77          discarded.  */
  78       {
  79         char buf[8];
  80         if (fread (buf, 1, 7, fp) < 7)
  81           goto skip;
  82         ASSERT (memcmp (buf, "foogars", 7) == 0);
  83       }
  84       /* Discard the buffered 'h'.  */
  85       if (check_filepos)
  86         ASSERT (ftell (fp) == 7);
  87       ASSERT (fpurge (fp) == 0);
  88       /* Verify that when discarding pending input, the file position is
  89          advanced to match the end of the previously read input.  */
  90       if (check_filepos)
  91         ASSERT (ftell (fp) == 8);
  92       ASSERT (getc (fp) == EOF);
  93       ASSERT (fclose (fp) == 0);
  94
  95       /* The file's contents is now "foogarsh".  */
  96
  97       /* Ensure that purging a read does not corrupt subsequent writes.  */
  98       fp = fopen (TESTFILE, "r+");
  99       if (fp == NULL)
 100         goto skip;
 101       if (fseek (fp, -1, SEEK_END))
 102         goto skip;
 103       ASSERT (getc (fp) == 'h');
 104       ASSERT (getc (fp) == EOF);
 105       if (check_filepos)
 106         ASSERT (ftell (fp) == 8);
 107       ASSERT (fpurge (fp) == 0);
 108       if (check_filepos)
 109         ASSERT (ftell (fp) == 8);
 110       ASSERT (putc ('!', fp) == '!');
 111       if (check_filepos)
 112         ASSERT (ftell (fp) == 9);
 113       ASSERT (fclose (fp) == 0);
 114       fp = fopen (TESTFILE, "r");
 115       if (fp == NULL)
 116         goto skip;
 117       {
 118         char buf[10];
 119         ASSERT (fread (buf, 1, 10, fp) == 9);
 120         ASSERT (memcmp (buf, "foogarsh!", 9) == 0);
 121       }
 122       ASSERT (fclose (fp) == 0);
 123
 124       /* The file's contents is now "foogarsh!".  */
 125     }
 126
 127   remove (TESTFILE);
 128   return test_exit_status;
 129
 130  skip:
 131   remove (TESTFILE);
 132   if (test_exit_status != EXIT_SUCCESS)
 133     return test_exit_status;
 134   fprintf (stderr, "Skipping test: prerequisite file operations failed.\n");
 135   return 77;
 136 }