295 lines
8.4 KiB
C
295 lines
8.4 KiB
C
/*
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* and/or other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/*
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FUNCTION
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<<fflush>>, <<fflush_unlocked>>---flush buffered file output
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INDEX
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fflush
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INDEX
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fflush_unlocked
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INDEX
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_fflush_r
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INDEX
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_fflush_unlocked_r
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SYNOPSIS
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#include <stdio.h>
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int fflush(FILE *<[fp]>);
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#define _BSD_SOURCE
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#include <stdio.h>
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int fflush_unlocked(FILE *<[fp]>);
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#include <stdio.h>
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int _fflush_r(struct _reent *<[reent]>, FILE *<[fp]>);
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#define _BSD_SOURCE
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#include <stdio.h>
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int _fflush_unlocked_r(struct _reent *<[reent]>, FILE *<[fp]>);
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DESCRIPTION
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The <<stdio>> output functions can buffer output before delivering it
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to the host system, in order to minimize the overhead of system calls.
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Use <<fflush>> to deliver any such pending output (for the file
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or stream identified by <[fp]>) to the host system.
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If <[fp]> is <<NULL>>, <<fflush>> delivers pending output from all
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open files.
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Additionally, if <[fp]> is a seekable input stream visiting a file
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descriptor, set the position of the file descriptor to match next
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unread byte, useful for obeying POSIX semantics when ending a process
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without consuming all input from the stream.
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<<fflush_unlocked>> is a non-thread-safe version of <<fflush>>.
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<<fflush_unlocked>> may only safely be used within a scope
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protected by flockfile() (or ftrylockfile()) and funlockfile(). This
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function may safely be used in a multi-threaded program if and only
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if they are called while the invoking thread owns the (FILE *)
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object, as is the case after a successful call to the flockfile() or
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ftrylockfile() functions. If threads are disabled, then
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<<fflush_unlocked>> is equivalent to <<fflush>>.
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The alternate functions <<_fflush_r>> and <<_fflush_unlocked_r>> are
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reentrant versions, where the extra argument <[reent]> is a pointer to
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a reentrancy structure, and <[fp]> must not be NULL.
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RETURNS
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<<fflush>> returns <<0>> unless it encounters a write error; in that
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situation, it returns <<EOF>>.
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PORTABILITY
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ANSI C requires <<fflush>>. The behavior on input streams is only
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specified by POSIX, and not all implementations follow POSIX rules.
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<<fflush_unlocked>> is a BSD extension also provided by GNU libc.
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No supporting OS subroutines are required.
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*/
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#include <_ansi.h>
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#include <stdio.h>
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#include <errno.h>
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#include "local.h"
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#ifdef __IMPL_UNLOCKED__
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#define _fflush_r _fflush_unlocked_r
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#define fflush fflush_unlocked
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#endif
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#ifndef __IMPL_UNLOCKED__
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/* Flush a single file, or (if fp is NULL) all files. */
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/* Core function which does not lock file pointer. This gets called
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directly from __srefill. */
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int
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__sflush_r (struct _reent *ptr,
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register FILE * fp)
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{
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register unsigned char *p;
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register _READ_WRITE_BUFSIZE_TYPE n;
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register _READ_WRITE_RETURN_TYPE t;
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short flags;
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flags = fp->_flags;
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if ((flags & __SWR) == 0)
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{
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#ifdef _FSEEK_OPTIMIZATION
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/* For a read stream, an fflush causes the next seek to be
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unoptimized (i.e. forces a system-level seek). This conforms
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to the POSIX and SUSv3 standards. */
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fp->_flags |= __SNPT;
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#endif
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/* For a seekable stream with buffered read characters, we will attempt
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a seek to the current position now. A subsequent read will then get
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the next byte from the file rather than the buffer. This conforms
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to the POSIX and SUSv3 standards. Note that the standards allow
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this seek to be deferred until necessary, but we choose to do it here
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to make the change simpler, more contained, and less likely
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to miss a code scenario. */
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if ((fp->_r > 0 || fp->_ur > 0) && fp->_seek != NULL)
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{
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int tmp_errno;
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#ifdef __LARGE64_FILES
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_fpos64_t curoff;
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#else
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_fpos_t curoff;
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#endif
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/* Save last errno and set errno to 0, so we can check if a device
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returns with a valid position -1. We restore the last errno if
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no other error condition has been encountered. */
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tmp_errno = ptr->_errno;
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ptr->_errno = 0;
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/* Get the physical position we are at in the file. */
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if (fp->_flags & __SOFF)
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curoff = fp->_offset;
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else
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{
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/* We don't know current physical offset, so ask for it.
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Only ESPIPE and EINVAL are ignorable. */
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#ifdef __LARGE64_FILES
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if (fp->_flags & __SL64)
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curoff = fp->_seek64 (ptr, fp->_cookie, 0, SEEK_CUR);
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else
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#endif
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curoff = fp->_seek (ptr, fp->_cookie, 0, SEEK_CUR);
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if (curoff == -1L && ptr->_errno != 0)
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{
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int result = EOF;
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if (ptr->_errno == ESPIPE || ptr->_errno == EINVAL)
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{
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result = 0;
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ptr->_errno = tmp_errno;
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}
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else
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fp->_flags |= __SERR;
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return result;
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}
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}
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if (fp->_flags & __SRD)
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{
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/* Current offset is at end of buffer. Compensate for
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characters not yet read. */
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curoff -= fp->_r;
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if (HASUB (fp))
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curoff -= fp->_ur;
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}
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/* Now physically seek to after byte last read. */
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#ifdef __LARGE64_FILES
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if (fp->_flags & __SL64)
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curoff = fp->_seek64 (ptr, fp->_cookie, curoff, SEEK_SET);
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else
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#endif
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curoff = fp->_seek (ptr, fp->_cookie, curoff, SEEK_SET);
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if (curoff != -1 || ptr->_errno == 0
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|| ptr->_errno == ESPIPE || ptr->_errno == EINVAL)
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{
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/* Seek successful or ignorable error condition.
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We can clear read buffer now. */
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#ifdef _FSEEK_OPTIMIZATION
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fp->_flags &= ~__SNPT;
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#endif
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fp->_r = 0;
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fp->_p = fp->_bf._base;
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if ((fp->_flags & __SOFF) && (curoff != -1 || ptr->_errno == 0))
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fp->_offset = curoff;
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ptr->_errno = tmp_errno;
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if (HASUB (fp))
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FREEUB (ptr, fp);
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}
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else
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{
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fp->_flags |= __SERR;
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return EOF;
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}
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}
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return 0;
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}
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if ((p = fp->_bf._base) == NULL)
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{
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/* Nothing to flush. */
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return 0;
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}
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n = fp->_p - p; /* write this much */
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/*
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* Set these immediately to avoid problems with longjmp
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* and to allow exchange buffering (via setvbuf) in user
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* write function.
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*/
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fp->_p = p;
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fp->_w = flags & (__SLBF | __SNBF) ? 0 : fp->_bf._size;
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while (n > 0)
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{
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t = fp->_write (ptr, fp->_cookie, (char *) p, n);
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if (t <= 0)
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{
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fp->_flags |= __SERR;
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return EOF;
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}
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p += t;
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n -= t;
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}
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return 0;
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}
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#ifdef _STDIO_BSD_SEMANTICS
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/* Called from _cleanup_r. At exit time, we don't need file locking,
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and we don't want to move the underlying file pointer unless we're
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writing. */
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int
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__sflushw_r (struct _reent *ptr,
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register FILE *fp)
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{
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return (fp->_flags & __SWR) ? __sflush_r (ptr, fp) : 0;
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}
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#endif
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#endif /* __IMPL_UNLOCKED__ */
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int
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_fflush_r (struct _reent *ptr,
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register FILE * fp)
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{
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int ret;
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#ifdef _REENT_SMALL
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/* For REENT_SMALL platforms, it is possible we are being
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called for the first time on a std stream. This std
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stream can belong to a reentrant struct that is not
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_REENT. If CHECK_INIT gets called below based on _REENT,
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we will end up changing said file pointers to the equivalent
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std stream off of _REENT. This causes unexpected behavior if
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there is any data to flush on the _REENT std stream. There
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are two alternatives to fix this: 1) make a reentrant fflush
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or 2) simply recognize that this file has nothing to flush
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and return immediately before performing a CHECK_INIT. Choice
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2 is implemented here due to its simplicity. */
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if (fp->_bf._base == NULL)
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return 0;
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#endif /* _REENT_SMALL */
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CHECK_INIT (ptr, fp);
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if (!fp->_flags)
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return 0;
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_newlib_flockfile_start (fp);
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ret = __sflush_r (ptr, fp);
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_newlib_flockfile_end (fp);
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return ret;
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}
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#ifndef _REENT_ONLY
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int
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fflush (register FILE * fp)
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{
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if (fp == NULL)
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return _fwalk_reent (_GLOBAL_REENT, _fflush_r);
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return _fflush_r (_REENT, fp);
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}
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#endif /* _REENT_ONLY */
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