text: /*	$NetBSD: setvbuf.c,v 1.19 2012/03/15 18:22:30 christos Exp $	*/
  
  /*-
   * 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. 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.
   */
  
  #include <sys/cdefs.h>
  #include <assert.h>
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <wchar.h>
  #include "reentrant.h"
  #include "local.h"
  
  /*
   * Set one of the three kinds of buffering, optionally including
   * a buffer.
   */
  int setvbuf(FILE *fp, char *buf, int mode, size_t size) {
    int ret, flags;
    size_t iosize;
    int ttyflag;
  
    _DIAGASSERT(fp != NULL);
    /* buf may be NULL */
  
    /*
     * 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 -1;
  
    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);
    WCIO_FREE(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 = -1;
        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;
    _DIAGASSERT(__type_fit(int, size));
    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 {
        _DIAGASSERT(__type_fit(int, size));
        fp->_w = (int)size;
      }
    } else {
      /* begin/continue reading, or stay in intermediate state */
      fp->_w = 0;
    }
    __cleanup = _cleanup;
  
    FUNLOCKFILE(fp);
    return ret;
  }
  