text: /*-
   * Copyright (c) 1990, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * This code is derived from software contributed to Berkeley by
   * Chris Torek.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #if defined(LIBC_SCCS) && !defined(lint)
  #if 0
  static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
  #endif
  static const char rcsid[] =
  		"$Id: setvbuf.c,v 1.1.1.1 2006/05/30 06:13:53 hhzhou Exp $";
  #endif /* LIBC_SCCS and not lint */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include "local.h"
  #include "libc_private.h"
  
  /*
   * Set one of the three kinds of buffering, optionally including
   * a buffer.
   */
  int
  setvbuf(fp, buf, mode, size)
  	register FILE *fp;
  	char *buf;
  	register int mode;
  	register size_t size;
  {
  	register int ret, flags;
  	size_t iosize;
  	int ttyflag;
  
  	/*
  	 * Verify arguments.  The `int' limit on `size' is due to this
  	 * particular implementation.  Note, buf and size are ignored
  	 * when setting _IONBF.
  	 */
  	if (mode != _IONBF)
  		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
  			return (EOF);
  
  	FLOCKFILE(fp);
  	/*
  	 * Write current buffer, if any.  Discard unread input (including
  	 * ungetc data), cancel line buffering, and free old buffer if
  	 * malloc()ed.  We also clear any eof condition, as if this were
  	 * a seek.
  	 */
  	ret = 0;
  	(void)__sflush(fp);
  	if (HASUB(fp))
  		FREEUB(fp);
  	fp->_r = fp->_lbfsize = 0;
  	flags = fp->_flags;
  	if (flags & __SMBF)
  		free((void *)fp->_bf._base);
  	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
  
  	/* If setting unbuffered mode, skip all the hard work. */
  	if (mode == _IONBF)
  		goto nbf;
  
  	/*
  	 * Find optimal I/O size for seek optimization.  This also returns
  	 * a `tty flag' to suggest that we check isatty(fd), but we do not
  	 * care since our caller told us how to buffer.
  	 */
  	flags |= __swhatbuf(fp, &iosize, &ttyflag);
  	if (size == 0) {
  		buf = NULL;	/* force local allocation */
  		size = iosize;
  	}
  
  	/* Allocate buffer if needed. */
  	if (buf == NULL) {
  		if ((buf = malloc(size)) == NULL) {
  			/*
  			 * Unable to honor user's request.  We will return
  			 * failure, but try again with file system size.
  			 */
  			ret = EOF;
  			if (size != iosize) {
  				size = iosize;
  				buf = malloc(size);
  			}
  		}
  		if (buf == NULL) {
  			/* No luck; switch to unbuffered I/O. */
  nbf:
  			fp->_flags = flags | __SNBF;
  			fp->_w = 0;
  			fp->_bf._base = fp->_p = fp->_nbuf;
  			fp->_bf._size = 1;
  			FUNLOCKFILE(fp);
  			return (ret);
  		}
  		flags |= __SMBF;
  	}
  
  	/*
  	 * Kill any seek optimization if the buffer is not the
  	 * right size.
  	 *
  	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
  	 */
  	if (size != iosize)
  		flags |= __SNPT;
  
  	/*
  	 * Fix up the FILE fields, and set __cleanup for output flush on
  	 * exit (since we are buffered in some way).
  	 */
  	if (mode == _IOLBF)
  		flags |= __SLBF;
  	fp->_flags = flags;
  	fp->_bf._base = fp->_p = (unsigned char *)buf;
  	fp->_bf._size = (int)size;
  	/* fp->_lbfsize is still 0 */
  	if (flags & __SWR) {
  		/*
  		 * Begin or continue writing: see __swsetup().  Note
  		 * that __SNBF is impossible (it was handled earlier).
  		 */
  		if (flags & __SLBF) {
  			fp->_w = 0;
  			fp->_lbfsize = -fp->_bf._size;
  		} else
  			fp->_w = (int)size;
  	} else {
  		/* begin/continue reading, or stay in intermediate state */
  		fp->_w = 0;
  	}
  	__cleanup = _cleanup;
  
  	FUNLOCKFILE(fp);
  	return (ret);
  }
  