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/* Test of fpurge() function.
Copyright (C) 2007-2023 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2007. */
#include <config.h>
/* None of the files accessed by this test are large, so disable the
fseek link warning if we are not using the gnulib fseek module. */
#define _GL_NO_LARGE_FILES
#include <stdio.h>
#include <string.h>
#include "macros.h"
#define TESTFILE "t-fpurge.tmp"
int
main (void)
{
int check_filepos;
for (check_filepos = 0; check_filepos <= 1; check_filepos++)
{
FILE *fp;
/* Create a file with some contents. */
fp = fopen (TESTFILE, "w");
if (fp == NULL)
goto skip;
if (fwrite ("foobarsh", 1, 8, fp) < 8)
goto skip;
if (fclose (fp))
goto skip;
/* The file's contents is now "foobarsh". */
/* Open it in read-write mode. */
fp = fopen (TESTFILE, "r+");
if (fp == NULL)
goto skip;
if (fseek (fp, 3, SEEK_CUR))
goto skip;
if (fwrite ("g", 1, 1, fp) < 1)
goto skip;
if (fflush (fp))
goto skip;
if (fwrite ("bz", 1, 2, fp) < 2)
goto skip;
/* Discard pending write. */
ASSERT (fpurge (fp) == 0);
/* Verify that when discarding pending output, the file position is set
back to where it was before the write calls. */
if (check_filepos)
ASSERT (ftell (fp) == 4);
ASSERT (fclose (fp) == 0);
/* Open it in read-only mode. */
fp = fopen (TESTFILE, "r");
if (fp == NULL)
goto skip;
/* Verify that the pending writes before the fpurge were really
discarded. */
{
char buf[8];
if (fread (buf, 1, 7, fp) < 7)
goto skip;
ASSERT (memcmp (buf, "foogars", 7) == 0);
}
/* Discard the buffered 'h'. */
if (check_filepos)
ASSERT (ftell (fp) == 7);
ASSERT (fpurge (fp) == 0);
/* Verify that when discarding pending input, the file position is
advanced to match the end of the previously read input. */
if (check_filepos)
ASSERT (ftell (fp) == 8);
ASSERT (getc (fp) == EOF);
ASSERT (fclose (fp) == 0);
/* The file's contents is now "foogarsh". */
/* Ensure that purging a read does not corrupt subsequent writes. */
fp = fopen (TESTFILE, "r+");
if (fp == NULL)
goto skip;
if (fseek (fp, -1, SEEK_END))
goto skip;
ASSERT (getc (fp) == 'h');
ASSERT (getc (fp) == EOF);
if (check_filepos)
ASSERT (ftell (fp) == 8);
ASSERT (fpurge (fp) == 0);
if (check_filepos)
ASSERT (ftell (fp) == 8);
ASSERT (putc ('!', fp) == '!');
if (check_filepos)
ASSERT (ftell (fp) == 9);
ASSERT (fclose (fp) == 0);
fp = fopen (TESTFILE, "r");
if (fp == NULL)
goto skip;
{
char buf[10];
ASSERT (fread (buf, 1, 10, fp) == 9);
ASSERT (memcmp (buf, "foogarsh!", 9) == 0);
}
ASSERT (fclose (fp) == 0);
/* The file's contents is now "foogarsh!". */
}
remove (TESTFILE);
return 0;
skip:
fprintf (stderr, "Skipping test: prerequisite file operations failed.\n");
remove (TESTFILE);
return 77;
}
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