132 lines
3.3 KiB
C
132 lines
3.3 KiB
C
/* Detect write error on a stream.
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Copyright (C) 2003-2005 Free Software Foundation, Inc.
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Written by Bruno Haible <bruno@clisp.org>, 2003.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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/* Specification. */
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#include "fwriteerror.h"
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#include <errno.h>
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#include <stdbool.h>
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int
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fwriteerror (FILE *fp)
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{
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/* State to allow multiple calls to fwriteerror (stdout). */
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static bool stdout_closed = false;
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if (fp == stdout && stdout_closed)
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return 0;
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/* Need to
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1. test the error indicator of the stream,
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2. flush the buffers both in userland and in the kernel, through fclose,
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testing for error again. */
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/* Clear errno, so that on non-POSIX systems the caller doesn't see a
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wrong value of errno when we return -1. */
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errno = 0;
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if (ferror (fp))
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{
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if (fflush (fp))
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return -1; /* errno is set here */
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/* The stream had an error earlier, but its errno was lost. If the
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error was not temporary, we can get the same errno by writing and
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flushing one more byte. We can do so because at this point the
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stream's contents is garbage anyway. */
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if (fputc ('\0', fp) == EOF)
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return -1; /* errno is set here */
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if (fflush (fp))
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return -1; /* errno is set here */
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/* Give up on errno. */
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errno = 0;
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return -1;
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}
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/* If we are closing stdout, don't attempt to do it later again. */
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if (fp == stdout)
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stdout_closed = true;
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if (fclose (fp))
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return -1; /* errno is set here */
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return 0;
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}
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#if TEST
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/* Name of a file on which writing fails. On systems without /dev/full,
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you can choose a filename on a full filesystem. */
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#define UNWRITABLE_FILE "/dev/full"
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int
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main ()
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{
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static int sizes[] =
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{
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511, 512, 513,
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1023, 1024, 1025,
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2047, 2048, 2049,
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4095, 4096, 4097,
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8191, 8192, 8193
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};
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static char dummy[8193];
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unsigned int i, j;
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for (i = 0; i < sizeof (sizes) / sizeof (sizes[0]); i++)
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{
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size_t size = sizes[i];
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for (j = 0; j < 2; j++)
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{
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/* Run a test depending on i and j:
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Write size bytes and then calls fflush if j==1. */
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FILE *stream = fopen (UNWRITABLE_FILE, "w");
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if (stream == NULL)
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{
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fprintf (stderr, "Test %u:%u: could not open file\n", i, j);
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continue;
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}
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fwrite (dummy, 347, 1, stream);
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fwrite (dummy, size - 347, 1, stream);
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if (j)
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fflush (stream);
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if (fwriteerror (stream) == -1)
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{
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if (errno != ENOSPC)
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fprintf (stderr, "Test %u:%u: fwriteerror ok, errno = %d\n",
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i, j, errno);
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}
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else
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fprintf (stderr, "Test %u:%u: fwriteerror found no error!\n",
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i, j);
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}
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}
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return 0;
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}
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#endif
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