/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2003, Trent Nelson, <trent@arpa.com>.
 * 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * 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 <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include "convtbl.h"

#define BIT             (8)
#define BITS            (1)
#define KILOBIT         (1000LL)
#define MEGABIT         (KILOBIT * 1000)
#define GIGABIT         (MEGABIT * 1000)
#define TERABIT         (GIGABIT * 1000)

#define BYTE            (1)
#define BYTES           (1)
#define KILOBYTE        (1024LL)
#define MEGABYTE        (KILOBYTE * 1024)
#define GIGABYTE        (MEGABYTE * 1024)
#define TERABYTE        (GIGABYTE * 1024)

struct convtbl {
        uintmax_t        mul;
        uintmax_t        scale;
        const char      *str;
        const char      *name;
};

static struct convtbl convtbl[] = {
        /* mul, scale, str, name */
        [SC_BYTE] =     { BYTE, BYTES, "B", "byte" },
        [SC_KILOBYTE] = { BYTE, KILOBYTE, "KB", "kbyte" },
        [SC_MEGABYTE] = { BYTE, MEGABYTE, "MB", "mbyte" },
        [SC_GIGABYTE] = { BYTE, GIGABYTE, "GB", "gbyte" },
        [SC_TERABYTE] = { BYTE, TERABYTE, "TB", "tbyte" },

        [SC_BIT] =      { BIT, BITS, "b", "bit" },
        [SC_KILOBIT] =  { BIT, KILOBIT, "Kb", "kbit" },
        [SC_MEGABIT] =  { BIT, MEGABIT, "Mb", "mbit" },
        [SC_GIGABIT] =  { BIT, GIGABIT, "Gb", "gbit" },
        [SC_TERABIT] =  { BIT, TERABIT, "Tb", "tbit" },

        [SC_AUTO] =     { 0, 0, "", "auto" }
};

static
struct convtbl *
get_tbl_ptr(const uintmax_t size, const int scale)
{
        uintmax_t        tmp;
        int              idx;

        /* If our index is out of range, default to auto-scaling. */
        idx = scale < SC_AUTO ? scale : SC_AUTO;

        if (idx == SC_AUTO)
                /*
                 * Simple but elegant algorithm.  Count how many times
                 * we can shift our size value right by a factor of ten,
                 * incrementing an index each time.  We then use the
                 * index as the array index into the conversion table.
                 */
                for (tmp = size, idx = SC_KILOBYTE;
                     tmp >= MEGABYTE && idx < SC_BIT - 1;
                     tmp >>= 10, idx++);

        return (&convtbl[idx]);
}

double
convert(const uintmax_t size, const int scale)
{
        struct convtbl  *tp;

        tp = get_tbl_ptr(size, scale);
        return ((double)size * tp->mul / tp->scale);

}

const char *
get_string(const uintmax_t size, const int scale)
{
        struct convtbl  *tp;

        tp = get_tbl_ptr(size, scale);
        return (tp->str);
}

int
get_scale(const char *name)
{
        int i;

        for (i = 0; i <= SC_AUTO; i++)
                if (strcmp(convtbl[i].name, name) == 0)
                        return (i);
        return (-1);
}

const char *
get_helplist(void)
{
        int i;
        size_t len;
        static char *buf;

        if (buf == NULL) {
                len = 0;
                for (i = 0; i <= SC_AUTO; i++)
                        len += strlen(convtbl[i].name) + 2;
                if ((buf = malloc(len)) != NULL) {
                        buf[0] = '\0';
                        for (i = 0; i <= SC_AUTO; i++) {
                                strcat(buf, convtbl[i].name);
                                if (i < SC_AUTO)
                                        strcat(buf, ", ");
                        }
                } else
                        return ("");
        }
        return (buf);
}