lib/fwriting.c

   1 /* Retrieve information about a FILE stream.
   2    Copyright (C) 2007-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation, either version 3 of the
   7    License, or (at your option) any later version.
   8
   9    This file 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 Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser 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 __fwriting function,
  25    namely glibc >= 2.2, Solaris >= 7, UnixWare >= 7.1.4.MP4, Cygwin >= 1.7.34,
  26    Android API >= 29, musl libc.  */
  27
  28 bool
  29 fwriting (FILE *fp)
  30 {
  31   /* Most systems provide FILE as a struct and the necessary bitmask in
  32      <stdio.h>, because they need it for implementing getc() and putc() as
  33      fast macros.  */
  34 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  35   /* GNU libc, BeOS, Haiku, Linux libc5 */
  36   return (fp->_flags & (_IO_NO_READS | _IO_CURRENTLY_PUTTING)) != 0;
  37 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  38   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin < 1.7.34, Minix 3, Android */
  39   return (fp_->_flags & __SWR) != 0;
  40 #elif defined __EMX__               /* emx+gcc */
  41   return (fp->_flags & _IOWRT) != 0;
  42 #elif defined __minix               /* Minix */
  43   return (fp->_flags & _IOWRITING) != 0;
  44 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
  45   return (fp_->_flag & _IOWRT) != 0;
  46 #elif defined __UCLIBC__            /* uClibc */
  47   return (fp->__modeflags & __FLAG_WRITING) != 0;
  48 #elif defined __QNX__               /* QNX */
  49   return ((fp->_Mode & 0x1 /* _MOPENR */) == 0
  50           || (fp->_Mode & 0x2000 /* _MWRITE */) != 0);
  51 #elif defined __MINT__              /* Atari FreeMiNT */
  52   if (!fp->__mode.__read)
  53     return 1;
  54   if (!fp->__mode.__write)
  55     return 0;
  56 # ifdef _IO_CURRENTLY_PUTTING /* Flag added on 2009-02-28 */
  57   return (fp->__flags & _IO_CURRENTLY_PUTTING) != 0;
  58 # else
  59   return (fp->__buffer < fp->__put_limit /*|| fp->__bufp == fp->__get_limit ??*/);
  60 # endif
  61 #elif defined EPLAN9                /* Plan9 */
  62   if (fp->state == 0 /* CLOSED */ || fp->state == 3 /* RD */)
  63     return 0;
  64   return (fp->state == 4 /* WR */ && (fp->bufl == 0 || fp->wp < fp->rp));
  65 #else
  66 # error "Please port gnulib fwriting.c to your platform!"
  67 #endif
  68 }