lib/fwriting.c

   1 /* Retrieve information about a FILE stream.
   2    Copyright (C) 2007-2020 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 #include <config.h>
  18
  19 /* Specification.  */
  20 #include "fwriting.h"
  21
  22 #include "stdio-impl.h"
  23
  24 /* This file is not used on systems that have the __fwritable function,
  25    namely glibc >= 2.2, Solaris >= 7, Android API >= 29, musl libc.  */
  26
  27 bool
  28 fwriting (FILE *fp)
  29 {
  30   /* Most systems provide FILE as a struct and the necessary bitmask in
  31      <stdio.h>, because they need it for implementing getc() and putc() as
  32      fast macros.  */
  33 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  34   /* GNU libc, BeOS, Haiku, Linux libc5 */
  35   return (fp->_flags & (_IO_NO_READS | _IO_CURRENTLY_PUTTING)) != 0;
  36 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  37   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
  38   return (fp_->_flags & __SWR) != 0;
  39 #elif defined __EMX__               /* emx+gcc */
  40   return (fp->_flags & _IOWRT) != 0;
  41 #elif defined __minix               /* Minix */
  42   return (fp->_flags & _IOWRITING) != 0;
  43 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel, OpenVMS */
  44   return (fp_->_flag & _IOWRT) != 0;
  45 #elif defined __UCLIBC__            /* uClibc */
  46   return (fp->__modeflags & __FLAG_WRITING) != 0;
  47 #elif defined __QNX__               /* QNX */
  48   return ((fp->_Mode & 0x1 /* _MOPENR */) == 0
  49           || (fp->_Mode & 0x2000 /* _MWRITE */) != 0);
  50 #elif defined __MINT__              /* Atari FreeMiNT */
  51   if (!fp->__mode.__read)
  52     return 1;
  53   if (!fp->__mode.__write)
  54     return 0;
  55 # ifdef _IO_CURRENTLY_PUTTING /* Flag added on 2009-02-28 */
  56   return (fp->__flags & _IO_CURRENTLY_PUTTING) != 0;
  57 # else
  58   return (fp->__buffer < fp->__put_limit /*|| fp->__bufp == fp->__get_limit ??*/);
  59 # endif
  60 #elif defined EPLAN9                /* Plan9 */
  61   if (fp->state == 0 /* CLOSED */ || fp->state == 3 /* RD */)
  62     return 0;
  63   return (fp->state == 4 /* WR */ && (fp->bufl == 0 || fp->wp < fp->rp));
  64 #else
  65 # error "Please port gnulib fwriting.c to your platform!"
  66 #endif
  67 }