/* * 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 <>---flush buffered file output INDEX fflush ANSI_SYNOPSIS #include int fflush(FILE *<[fp]>); int _fflush_r(struct _reent *<[reent]>, FILE *<[fp]>); DESCRIPTION The <> output functions can buffer output before delivering it to the host system, in order to minimize the overhead of system calls. Use <> to deliver any such pending output (for the file or stream identified by <[fp]>) to the host system. If <[fp]> is <>, <> 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 <> returns <<0>> unless it encounters a write error; in that situation, it returns <>. PORTABILITY ANSI C requires <>. 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 #include #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); _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; #ifdef __LARGE64_FILES _fpos64_t curoff; #else _fpos_t curoff; #endif /* 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 is 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) { int result = EOF; if (ptr->_errno == ESPIPE) result = 0; 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) tmp = (fp->_seek64 (ptr, fp->_cookie, curoff, SEEK_SET) == curoff); else #endif tmp = (fp->_seek (ptr, fp->_cookie, curoff, SEEK_SET) == curoff); if (tmp) { /* Seek successful. We can clear read buffer now. */ fp->_flags &= ~__SNPT; fp->_r = 0; fp->_p = fp->_bf._base; if (fp->_flags & __SOFF) fp->_offset = curoff; } 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 */