/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2012 Jeremie Le Hen <jlh@FreeBSD.org>
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <err.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static const char *
stream_name(FILE *s)
{

        if (s == stdin)
                return "stdin";
        if (s == stdout)
                return "stdout";
        if (s == stderr)
                return "stderr";
        /* This should not happen. */
        abort();
}

static void
change_buf(FILE *s, const char *bufmode)
{
        char *unit;
        size_t bufsize;
        int mode;

        bufsize = 0;
        if (bufmode[0] == '0' && bufmode[1] == '\0')
                mode = _IONBF;
        else if (bufmode[0] == 'L' && bufmode[1] == '\0')
                mode = _IOLBF;
        else if (bufmode[0] == 'B' && bufmode[1] == '\0') {
                mode = _IOFBF;
                bufsize = 0;
        } else {
                /*
                 * This library being preloaded, depending on libutil
                 * would lead to excessive namespace pollution.
                 * Thus we do not use expand_number().
                 */
                errno = 0;
                bufsize = strtol(bufmode, &unit, 0);
                if (errno == EINVAL || errno == ERANGE || unit == bufmode)
                        warn("Wrong buffer mode '%s' for %s", bufmode,
                            stream_name(s));
                switch (*unit) {
                case 'G':
                        bufsize *= 1024 * 1024 * 1024;
                        break;
                case 'M':
                        bufsize *= 1024 * 1024;
                        break;
                case 'k':
                        bufsize *= 1024;
                        break;
                case '\0':
                        break;
                default:
                        warnx("Unknown suffix '%c' for %s", *unit,
                            stream_name(s));
                        return;
                }
                mode = _IOFBF;
        }
        if (setvbuf(s, NULL, mode, bufsize) != 0)
                warn("Cannot set buffer mode '%s' for %s", bufmode,
                    stream_name(s));
}

__attribute__ ((constructor)) static void
stdbuf(void)
{
        char *i_mode, *o_mode, *e_mode;

        i_mode = getenv("_STDBUF_I");
        o_mode = getenv("_STDBUF_O");
        e_mode = getenv("_STDBUF_E");

        if (e_mode != NULL)
                change_buf(stderr, e_mode);
        if (i_mode != NULL)
                change_buf(stdin, i_mode);
        if (o_mode != NULL)
                change_buf(stdout, o_mode);
}