/* Flushing buffers of a FILE stream.

   Copyright (C) 2007-2018 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include <stdio.h>

#if HAVE___FPURGE                   /* glibc >= 2.2, Haiku, Solaris >= 7, Android API >= 23 */

# include <stdio_ext.h>

#endif

#include <stdlib.h>

#include "stdio-impl.h"

int

fpurge (FILE *fp)

{

#if HAVE___FPURGE                   /* glibc >= 2.2, Haiku, Solaris >= 7, Android API >= 23, musl libc */

  __fpurge (fp);

  /* The __fpurge function does not have a return value.  */

  return 0;

#elif HAVE_FPURGE                   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin 1.7 */

  /* Call the system's fpurge function.  */

# undef fpurge

# if !HAVE_DECL_FPURGE

  extern int fpurge (FILE *);

# endif

  int result = fpurge (fp);

# if defined __sferror || defined __DragonFly__ || defined __ANDROID__

  /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */

  if (result == 0)

    /* Correct the invariants that fpurge broke.

       <stdio.h> on BSD systems says:

         "The following always hold: if _flags & __SRD, _w is 0."

       If this invariant is not fulfilled and the stream is read-write but

       currently reading, subsequent putc or fputc calls will write directly

       into the buffer, although they shouldn't be allowed to.  */

    if ((fp_->_flags & __SRD) != 0)

      fp_->_w = 0;

# endif

  return result;

#else

  /* Most systems provide FILE as a struct and the necessary bitmask in

     <stdio.h>, because they need it for implementing getc() and putc() as

     fast macros.  */

# if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1

  /* GNU libc, BeOS, Haiku, Linux libc5 */

  fp->_IO_read_end = fp->_IO_read_ptr;

  fp->_IO_write_ptr = fp->_IO_write_base;

  /* Avoid memory leak when there is an active ungetc buffer.  */

  if (fp->_IO_save_base != NULL)

    {

      free (fp->_IO_save_base);

      fp->_IO_save_base = NULL;

    }

  return 0;

# elif defined __sferror || defined __DragonFly__ || defined __ANDROID__

  /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */

  fp_->_p = fp_->_bf._base;

  fp_->_r = 0;

  fp_->_w = ((fp_->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */

             ? fp_->_bf._size

             : 0);

  /* Avoid memory leak when there is an active ungetc buffer.  */

  if (fp_ub._base != NULL)

    {

      if (fp_ub._base != fp_->_ubuf)

        free (fp_ub._base);

      fp_ub._base = NULL;

    }

  return 0;

# elif defined __EMX__              /* emx+gcc */

  fp->_ptr = fp->_buffer;

  fp->_rcount = 0;

  fp->_wcount = 0;

  fp->_ungetc_count = 0;

  return 0;

# elif defined __minix              /* Minix */

  fp->_ptr = fp->_buf;

  if (fp->_ptr != NULL)

    fp->_count = 0;

  return 0;

# elif defined _IOERR               /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel, OpenVMS */

  fp_->_ptr = fp_->_base;

  if (fp_->_ptr != NULL)

    fp_->_cnt = 0;

  return 0;

# elif defined __UCLIBC__           /* uClibc */

#  ifdef __STDIO_BUFFERS

  if (fp->__modeflags & __FLAG_WRITING)

    fp->__bufpos = fp->__bufstart;

  else if (fp->__modeflags & (__FLAG_READONLY | __FLAG_READING))

    fp->__bufpos = fp->__bufread;

#  endif

  return 0;

# elif defined __QNX__              /* QNX */

  fp->_Rback = fp->_Back + sizeof (fp->_Back);

  fp->_Rsave = NULL;

  if (fp->_Mode & 0x2000 /* _MWRITE */)

    /* fp->_Buf <= fp->_Next <= fp->_Wend */

    fp->_Next = fp->_Buf;

  else

    /* fp->_Buf <= fp->_Next <= fp->_Rend */

    fp->_Rend = fp->_Next;

  return 0;

# elif defined __MINT__             /* Atari FreeMiNT */

  if (fp->__pushed_back)

    {

      fp->__bufp = fp->__pushback_bufp;

      fp->__pushed_back = 0;

    }

  /* Preserve the current file position.  */

  if (fp->__target != -1)

    fp->__target += fp->__bufp - fp->__buffer;

  fp->__bufp = fp->__buffer;

  /* Nothing in the buffer, next getc is nontrivial.  */

  fp->__get_limit = fp->__bufp;

  /* Nothing in the buffer, next putc is nontrivial.  */

  fp->__put_limit = fp->__buffer;

  return 0;

# elif defined EPLAN9               /* Plan9 */

  fp->rp = fp->wp = fp->lp = fp->buf;

  return 0;

# else

#  error "Please port gnulib fpurge.c to your platform! Look at the definitions of fflush, setvbuf and ungetc on your system, then report this to bug-gnulib."

# endif

#endif

}