libio/iofgets.c

   1 /* Copyright (C) 1993, 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2005
   2    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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.
  19
  20    As a special exception, if you link the code in this file with
  21    files compiled with a GNU compiler to produce an executable,
  22    that does not cause the resulting executable to be covered by
  23    the GNU Lesser General Public License.  This exception does not
  24    however invalidate any other reasons why the executable file
  25    might be covered by the GNU Lesser General Public License.
  26    This exception applies to code released by its copyright holders
  27    in files containing the exception.  */
  28
  29 #include "libioP.h"
  30 #include <stdio.h>
  31
  32 char *
  33 _IO_fgets (buf, n, fp)
  34      char *buf;
  35      int n;
  36      _IO_FILE *fp;
  37 {
  38   _IO_size_t count;
  39   char *result;
  40   int old_error;
  41   CHECK_FILE (fp, NULL);
  42   if (n <= 0)
  43     return NULL;
  44   if (__builtin_expect (n == 1, 0))
  45     {
  46       /* Another irregular case: since we have to store a NUL byte and
  47          there is only room for exactly one byte, we don't have to
  48          read anything.  */
  49       buf[0] = '\0';
  50       return buf;
  51     }
  52   _IO_acquire_lock (fp);
  53   /* This is very tricky since a file descriptor may be in the
  54      non-blocking mode. The error flag doesn't mean much in this
  55      case. We return an error only when there is a new error. */
  56   old_error = fp->_IO_file_flags & _IO_ERR_SEEN;
  57   fp->_IO_file_flags &= ~_IO_ERR_SEEN;
  58   count = INTUSE(_IO_getline) (fp, buf, n - 1, '\n', 1);
  59   /* If we read in some bytes and errno is EAGAIN, that error will
  60      be reported for next read. */
  61   if (count == 0 || ((fp->_IO_file_flags & _IO_ERR_SEEN)
  62                      && errno != EAGAIN))
  63     result = NULL;
  64   else
  65     {
  66       buf[count] = '\0';
  67       result = buf;
  68     }
  69   fp->_IO_file_flags |= old_error;
  70   _IO_release_lock (fp);
  71   return result;
  72 }
  73
  74 #ifdef weak_alias
  75 weak_alias (_IO_fgets, fgets)
  76
  77 # ifndef _IO_MTSAFE_IO
  78 weak_alias (_IO_fgets, fgets_unlocked)
  79 libc_hidden_weak (fgets_unlocked)
  80 # endif
  81 #endif