/*      $OpenBSD: setvbuf.c,v 1.16 2025/08/08 15:58:53 yasuoka 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 <limits.h>
#include <stdio.h>
#include <stdlib.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;

        /*
         * 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) || size > INT_MAX)
                        return (EOF);

        /*
         * 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.
         */
        FLOCKFILE(fp);
        ret = 0;
        (void)__sflush(fp);
        if (HASUB(fp))
                FREEUB(fp);
        fp->_ungetwc_inbuf = 0;
        fp->_r = fp->_lbfsize = 0;
        flags = fp->_flags;
        if (flags & __SMBF)
                free(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;
        }

        /*
         * We're committed to buffering from here, so make sure we've
         * registered to flush buffers on exit.
         */
        if (!__sdidinit)
                __sinit();

        /*
         * 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 = 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 = size;
        } else {
                /* begin/continue reading, or stay in intermediate state */
                fp->_w = 0;
        }
        FUNLOCKFILE(fp);

        return (ret);
}
DEF_STRONG(setvbuf);