lib/fwriting.h

   1 /* Retrieve information about a FILE stream.
   2    Copyright (C) 2007, 2009-2019 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 <stdbool.h>
  18 #include <stdio.h>
  19
  20 /* Return true if the stream STREAM is opened write-only or
  21    append-only, or if the last operation on the stream was a write
  22    operation.  Return false if the stream is opened read-only, or if
  23    it supports reading and there is no current write operation (such
  24    as fputc).
  25
  26    freading and fwriting will never both be true.  If STREAM supports
  27    both reads and writes, then:
  28      - both freading and fwriting might be false when the stream is first
  29        opened, after read encounters EOF, or after fflush,
  30      - freading might be false or true and fwriting might be false
  31        after repositioning (such as fseek, fsetpos, or rewind),
  32    depending on the underlying implementation.
  33
  34    STREAM must not be wide-character oriented.  */
  35
  36 #if HAVE___FWRITING /* glibc >= 2.2, Solaris >= 7, Android API >= 29, musl libc */
  37
  38 # include <stdio_ext.h>
  39 # define fwriting(stream) (__fwriting (stream) != 0)
  40
  41 #else
  42
  43 # ifdef __cplusplus
  44 extern "C" {
  45 # endif
  46
  47 extern bool fwriting (FILE *stream) _GL_ATTRIBUTE_PURE;
  48
  49 # ifdef __cplusplus
  50 }
  51 # endif
  52
  53 #endif