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/*

 * Copyright (c) 1990 The Regents of the University of California.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms are permitted

 * provided that the above copyright notice and this paragraph are

 * duplicated in all such forms and that any documentation,

 * advertising materials, and other materials related to such

 * distribution and use acknowledge that the software was developed

 * by the University of California, Berkeley.  The name of the

 * University may not be used to endorse or promote products derived

 * from this software without specific prior written permission.

 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 */

/*

FUNCTION

<<fflush>>---flush buffered file output

INDEX

        fflush

INDEX

        _fflush_r

ANSI_SYNOPSIS

        #include <stdio.h>

        int fflush(FILE *<[fp]>);

        int _fflush_r(struct _reent *<[reent]>, FILE *<[fp]>);

DESCRIPTION

The <<stdio>> output functions can buffer output before delivering it

to the host system, in order to minimize the overhead of system calls.

Use <<fflush>> to deliver any such pending output (for the file

or stream identified by <[fp]>) to the host system.

If <[fp]> is <<NULL>>, <<fflush>> delivers pending output from all

open files.

Additionally, if <[fp]> is a seekable input stream visiting a file

descriptor, set the position of the file descriptor to match next

unread byte, useful for obeying POSIX semantics when ending a process

without consuming all input from the stream.

The alternate function <<_fflush_r>> is a reentrant version, where the

extra argument <[reent]> is a pointer to a reentrancy structure, and

<[fp]> must not be NULL.

RETURNS

<<fflush>> returns <<0>> unless it encounters a write error; in that

situation, it returns <<EOF>>.

PORTABILITY

ANSI C requires <<fflush>>.  The behavior on input streams is only

specified by POSIX, and not all implementations follow POSIX rules.

No supporting OS subroutines are required.

*/

#include <_ansi.h>

#include <stdio.h>

#include <errno.h>

#include "local.h"

/* Flush a single file, or (if fp is NULL) all files.  */

int

_DEFUN(_fflush_r, (ptr, fp),

       struct _reent *ptr _AND

       register FILE * fp)

{

  register unsigned char *p;

  register int n, t;

#ifdef _REENT_SMALL

  /* For REENT_SMALL platforms, it is possible we are being

     called for the first time on a std stream.  This std

     stream can belong to a reentrant struct that is not

     _REENT.  If CHECK_INIT gets called below based on _REENT,

     we will end up changing said file pointers to the equivalent

     std stream off of _REENT.  This causes unexpected behavior if

     there is any data to flush on the _REENT std stream.  There

     are two alternatives to fix this:  1) make a reentrant fflush

     or 2) simply recognize that this file has nothing to flush

     and return immediately before performing a CHECK_INIT.  Choice

     2 is implemented here due to its simplicity.  */

  if (fp->_bf._base == NULL)

    return 0;

#endif /* _REENT_SMALL  */

  CHECK_INIT (ptr, fp);

  if (!fp->_flags)

    return 0;

  _flockfile (fp);

  t = fp->_flags;

  if ((t & __SWR) == 0)

    {

      /* For a read stream, an fflush causes the next seek to be

         unoptimized (i.e. forces a system-level seek).  This conforms

         to the POSIX and SUSv3 standards.  */

      fp->_flags |= __SNPT;

      /* For a seekable stream with buffered read characters, we will attempt

         a seek to the current position now.  A subsequent read will then get

         the next byte from the file rather than the buffer.  This conforms

         to the POSIX and SUSv3 standards.  Note that the standards allow

         this seek to be deferred until necessary, but we choose to do it here

         to make the change simpler, more contained, and less likely

         to miss a code scenario.  */

      if ((fp->_r > 0 || fp->_ur > 0) && fp->_seek != NULL)

        {

          int tmp_errno;

#ifdef __LARGE64_FILES

          _fpos64_t curoff;

#else

          _fpos_t curoff;

#endif

          /* Save last errno and set errno to 0, so we can check if a device

             returns with a valid position -1.  We restore the last errno if

             no other error condition has been encountered. */

          tmp_errno = ptr->_errno;

          ptr->_errno = 0;

          /* Get the physical position we are at in the file.  */

          if (fp->_flags & __SOFF)

            curoff = fp->_offset;

          else

            {

              /* We don't know current physical offset, so ask for it.

                 Only ESPIPE and EINVAL are ignorable.  */

#ifdef __LARGE64_FILES

              if (fp->_flags & __SL64)

                curoff = fp->_seek64 (ptr, fp->_cookie, 0, SEEK_CUR);

              else

#endif

                curoff = fp->_seek (ptr, fp->_cookie, 0, SEEK_CUR);

              if (curoff == -1L && ptr->_errno != 0)

                {

                  int result = EOF;

                  if (ptr->_errno == ESPIPE || ptr->_errno == EINVAL)

                    {

                      result = 0;

                      ptr->_errno = tmp_errno;

                    }

                  else

                    fp->_flags |= __SERR;

                  _funlockfile (fp);

                  return result;

                }

            }

          if (fp->_flags & __SRD)

            {

              /* Current offset is at end of buffer.  Compensate for

                 characters not yet read.  */

              curoff -= fp->_r;

              if (HASUB (fp))

                curoff -= fp->_ur;

            }

          /* Now physically seek to after byte last read.  */

#ifdef __LARGE64_FILES

          if (fp->_flags & __SL64)

            curoff = fp->_seek64 (ptr, fp->_cookie, curoff, SEEK_SET);

          else

#endif

            curoff = fp->_seek (ptr, fp->_cookie, curoff, SEEK_SET);

          if (curoff != -1 || ptr->_errno == 0

              || ptr->_errno == ESPIPE || ptr->_errno == EINVAL)

            {

              /* Seek successful or ignorable error condition.

                 We can clear read buffer now.  */

              fp->_flags &= ~__SNPT;

              fp->_r = 0;

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

              if ((fp->_flags & __SOFF) && (curoff != -1 || ptr->_errno == 0))

                fp->_offset = curoff;

              ptr->_errno = tmp_errno;

              if (HASUB (fp))

                FREEUB (ptr, fp);

            }

          else

            {

              fp->_flags |= __SERR;

              _funlockfile (fp);

              return EOF;

            }

        }

      _funlockfile (fp);

      return 0;

    }

  if ((p = fp->_bf._base) == NULL)

    {

      /* Nothing to flush.  */

      _funlockfile (fp);

      return 0;

    }

  n = fp->_p - p;               /* write this much */

  /*

   * Set these immediately to avoid problems with longjmp

   * and to allow exchange buffering (via setvbuf) in user

   * write function.

   */

  fp->_p = p;

  fp->_w = t & (__SLBF | __SNBF) ? 0 : fp->_bf._size;

  while (n > 0)

    {

      t = fp->_write (ptr, fp->_cookie, (char *) p, n);

      if (t <= 0)

        {

          fp->_flags |= __SERR;

          _funlockfile (fp);

          return EOF;

        }

      p += t;

      n -= t;

    }

  _funlockfile (fp);

  return 0;

}

#ifndef _REENT_ONLY

int

_DEFUN(fflush, (fp),

       register FILE * fp)

{

  if (fp == NULL)

    return _fwalk_reent (_GLOBAL_REENT, _fflush_r);

  return _fflush_r (_REENT, fp);

}

#endif /* _REENT_ONLY */