/*      $NetBSD: makebuf.c,v 1.19 2018/12/14 03:29:54 uwe 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>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)makebuf.c   8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: makebuf.c,v 1.19 2018/12/14 03:29:54 uwe Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <ctype.h>
#include "reentrant.h"
#include "local.h"

/*
 * Override the file buffering based on the environment setting STDBUF%d
 * (for the specific file descriptor) and STDBUF (for all descriptors).
 * the setting is ULF<num> standing for "Unbuffered", "Linebuffered",
 * and Fullybuffered", and <num> is a value from 0 to 1M.
 */
static int
__senvbuf(FILE *fp, size_t *size, int *couldbetty)
{
        char evb[64], *evp;
        int flags, e;
        intmax_t s;

        flags = 0;
        if (snprintf(evb, sizeof(evb), "STDBUF%d", fp->_file) < 0)
                return flags;

        if ((evp = getenv(evb)) == NULL && (evp = getenv("STDBUF")) == NULL)
                return flags;

        switch (*evp) {
        case 'u':
        case 'U':
                evp++;
                flags |= __SNBF;
                break;
        case 'l':
        case 'L':
                evp++;
                flags |= __SLBF;
                break;
        case 'f':
        case 'F':
                evp++;
                *couldbetty = 0;
                break;
        }

        if (!isdigit((unsigned char)*evp))
                return flags;

        s = strtoi(evp, NULL, 0, 0, 1024 * 1024, &e);
        if (e != 0)
                return flags;

        *size = (size_t)s;
        if (*size == 0)
                return __SNBF;

        return flags;
}

/*
 * Allocate a file buffer, or switch to unbuffered I/O.
 * Per the ANSI C standard, ALL tty devices default to line buffered.
 *
 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
 * optimisation) right after the fstat() that finds the buffer size.
 */
void
__smakebuf(FILE *fp)
{
        void *p;
        int flags;
        size_t size;
        int couldbetty;

        _DIAGASSERT(fp != NULL);

        if (fp->_flags & __SNBF)
                goto unbuf;

        flags = __swhatbuf(fp, &size, &couldbetty);

        if ((fp->_flags & (__SLBF|__SNBF|__SMBF)) == 0
            && fp->_cookie == fp && fp->_file >= 0) {
                flags |= __senvbuf(fp, &size, &couldbetty);
                if (flags & __SNBF)
                        goto unbuf;
        }

        if ((p = malloc(size)) == NULL)
                goto unbuf;

        __cleanup = _cleanup;
        flags |= __SMBF;
        fp->_bf._base = fp->_p = p;
        _DIAGASSERT(__type_fit(int, size));
        fp->_bf._size = (int)size;
        if (couldbetty && isatty(__sfileno(fp)))
                flags |= __SLBF;
        fp->_flags |= flags;
        return;
unbuf:
        fp->_flags |= __SNBF;
        fp->_bf._base = fp->_p = fp->_nbuf;
        fp->_bf._size = 1;
}

/*
 * Internal routine to determine `proper' buffering for a file.
 */
int
__swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
{
        struct stat st;

        _DIAGASSERT(fp != NULL);
        _DIAGASSERT(bufsize != NULL);
        _DIAGASSERT(couldbetty != NULL);

        if (__sfileno(fp) == -1 || fstat(__sfileno(fp), &st) < 0) {
                *couldbetty = 0;
                *bufsize = BUFSIZ;
                return __SNPT;
        }

        /* could be a tty iff it is a character device */
        *couldbetty = S_ISCHR(st.st_mode);
        if (st.st_blksize == 0) {
                *bufsize = BUFSIZ;
                return __SNPT;
        }

        /*
         * Optimise fseek() only if it is a regular file.  (The test for
         * __sseek is mainly paranoia.)  It is safe to set _blksize
         * unconditionally; it will only be used if __SOPT is also set.
         */
        *bufsize = st.st_blksize;
        fp->_blksize = st.st_blksize;
        return (st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
            __SOPT : __SNPT;
}