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glibc  2.9
fgets_chk.c
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00001 /* Copyright (C) 1993, 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2005
00002    Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.
00019 
00020    As a special exception, if you link the code in this file with
00021    files compiled with a GNU compiler to produce an executable,
00022    that does not cause the resulting executable to be covered by
00023    the GNU Lesser General Public License.  This exception does not
00024    however invalidate any other reasons why the executable file
00025    might be covered by the GNU Lesser General Public License.
00026    This exception applies to code released by its copyright holders
00027    in files containing the exception.  */
00028 
00029 #include "libioP.h"
00030 #include <stdio.h>
00031 #include <sys/param.h>
00032 
00033 char *
00034 __fgets_chk (buf, size, n, fp)
00035      char *buf;
00036      size_t size;
00037      int n;
00038      _IO_FILE *fp;
00039 {
00040   _IO_size_t count;
00041   char *result;
00042   CHECK_FILE (fp, NULL);
00043   if (n <= 0)
00044     return NULL;
00045   _IO_acquire_lock (fp);
00046   /* This is very tricky since a file descriptor may be in the
00047      non-blocking mode. The error flag doesn't mean much in this
00048      case. We return an error only when there is a new error. */
00049   int old_error = fp->_IO_file_flags & _IO_ERR_SEEN;
00050   fp->_IO_file_flags &= ~_IO_ERR_SEEN;
00051   count = INTUSE(_IO_getline) (fp, buf, MIN ((size_t) n - 1, size), '\n', 1);
00052   /* If we read in some bytes and errno is EAGAIN, that error will
00053      be reported for next read. */
00054   if (count == 0 || ((fp->_IO_file_flags & _IO_ERR_SEEN)
00055                    && errno != EAGAIN))
00056     result = NULL;
00057   else if (count >= size)
00058     __chk_fail ();
00059   else
00060     {
00061       buf[count] = '\0';
00062       result = buf;
00063     }
00064   fp->_IO_file_flags |= old_error;
00065   _IO_release_lock (fp);
00066   return result;
00067 }