/*      $OpenBSD: fmt_scaled.c,v 1.23 2022/12/27 17:10:08 jmc Exp $     */

/*
 * Copyright (c) 2001, 2002, 2003 Ian F. Darwin.  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 ``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 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.
 */

/*
 * fmt_scaled: Format numbers scaled for human comprehension
 * scan_scaled: Scan numbers in this format.
 *
 * "Human-readable" output uses 4 digits max, and puts a unit suffix at
 * the end.  Makes output compact and easy-to-read esp. on huge disks.
 * Formatting code was originally in OpenBSD "df", converted to library routine.
 * Scanning code written for OpenBSD libutil.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>

#include "util.h"

typedef enum {
        NONE = 0, KILO = 1, MEGA = 2, GIGA = 3, TERA = 4, PETA = 5, EXA = 6
} unit_type;

/* These three arrays MUST be in sync!  XXX make a struct */
static const unit_type units[] = { NONE, KILO, MEGA, GIGA, TERA, PETA, EXA };
static const char scale_chars[] = "BKMGTPE";
static const long long scale_factors[] = {
        1LL,
        1024LL,
        1024LL*1024,
        1024LL*1024*1024,
        1024LL*1024*1024*1024,
        1024LL*1024*1024*1024*1024,
        1024LL*1024*1024*1024*1024*1024,
};
#define SCALE_LENGTH (sizeof(units)/sizeof(units[0]))

#define MAX_DIGITS (SCALE_LENGTH * 3)   /* XXX strlen(sprintf("%lld", -1)? */

/* Convert the given input string "scaled" into numeric in "result".
 * Return 0 on success, -1 and errno set on error.
 */
int
scan_scaled(char *scaled, long long *result)
{
        char *p = scaled;
        int sign = 0;
        unsigned int i, ndigits = 0, fract_digits = 0;
        long long scale_fact = 1, whole = 0, fpart = 0;

        /* Skip leading whitespace */
        while (isascii((unsigned char)*p) && isspace((unsigned char)*p))
                ++p;

        /* Then at most one leading + or - */
        while (*p == '-' || *p == '+') {
                if (*p == '-') {
                        if (sign) {
                                errno = EINVAL;
                                return -1;
                        }
                        sign = -1;
                        ++p;
                } else if (*p == '+') {
                        if (sign) {
                                errno = EINVAL;
                                return -1;
                        }
                        sign = +1;
                        ++p;
                }
        }

        /* Main loop: Scan digits, find decimal point, if present.
         * We don't allow exponentials, so no scientific notation
         * (but note that E for Exa might look like e to some!).
         * Advance 'p' to end, to get scale factor.
         */
        for (; isascii((unsigned char)*p) &&
            (isdigit((unsigned char)*p) || *p=='.'); ++p) {
                if (*p == '.') {
                        if (fract_digits > 0) { /* oops, more than one '.' */
                                errno = EINVAL;
                                return -1;
                        }
                        fract_digits = 1;
                        continue;
                }

                i = (*p) - '0';                 /* whew! finally a digit we can use */
                if (fract_digits > 0) {
                        if (fract_digits >= MAX_DIGITS-1)
                                /* ignore extra fractional digits */
                                continue;
                        fract_digits++;         /* for later scaling */
                        if (fpart > LLONG_MAX / 10) {
                                errno = ERANGE;
                                return -1;
                        }
                        fpart *= 10;
                        if (i > LLONG_MAX - fpart) {
                                errno = ERANGE;
                                return -1;
                        }
                        fpart += i;
                } else {                                /* normal digit */
                        if (++ndigits >= MAX_DIGITS) {
                                errno = ERANGE;
                                return -1;
                        }
                        if (whole > LLONG_MAX / 10) {
                                errno = ERANGE;
                                return -1;
                        }
                        whole *= 10;
                        if (i > LLONG_MAX - whole) {
                                errno = ERANGE;
                                return -1;
                        }
                        whole += i;
                }
        }

        if (sign)
                whole *= sign;

        /* If no scale factor given, we're done. fraction is discarded. */
        if (!*p) {
                *result = whole;
                return 0;
        }

        /* Validate scale factor, and scale whole and fraction by it. */
        for (i = 0; i < SCALE_LENGTH; i++) {

                /* Are we there yet? */
                if (*p == scale_chars[i] ||
                        *p == tolower((unsigned char)scale_chars[i])) {

                        /* If it ends with alphanumerics after the scale char, bad. */
                        if (isalnum((unsigned char)*(p+1))) {
                                errno = EINVAL;
                                return -1;
                        }
                        scale_fact = scale_factors[i];

                        /* check for overflow and underflow after scaling */
                        if (whole > LLONG_MAX / scale_fact ||
                            whole < LLONG_MIN / scale_fact) {
                                errno = ERANGE;
                                return -1;
                        }

                        /* scale whole part */
                        whole *= scale_fact;

                        /* truncate fpart so it doesn't overflow.
                         * then scale fractional part.
                         */
                        while (fpart >= LLONG_MAX / scale_fact) {
                                fpart /= 10;
                                fract_digits--;
                        }
                        fpart *= scale_fact;
                        if (fract_digits > 0) {
                                for (i = 0; i < fract_digits -1; i++)
                                        fpart /= 10;
                        }
                        if (sign == -1)
                                whole -= fpart;
                        else
                                whole += fpart;
                        *result = whole;
                        return 0;
                }
        }

        /* Invalid unit or character */
        errno = EINVAL;
        return -1;
}

/* Format the given "number" into human-readable form in "result".
 * Result must point to an allocated buffer of length FMT_SCALED_STRSIZE.
 * Return 0 on success, -1 and errno set if error.
 */
int
fmt_scaled(long long number, char *result)
{
        long long abval, fract = 0;
        unsigned int i;
        unit_type unit = NONE;

        /* Not every negative long long has a positive representation. */
        if (number == LLONG_MIN) {
                errno = ERANGE;
                return -1;
        }

        abval = llabs(number);

        /* Also check for numbers that are just too darned big to format. */
        if (abval / 1024 >= scale_factors[SCALE_LENGTH-1]) {
                errno = ERANGE;
                return -1;
        }

        /* scale whole part; get unscaled fraction */
        for (i = 0; i < SCALE_LENGTH; i++) {
                if (abval/1024 < scale_factors[i]) {
                        unit = units[i];
                        fract = (i == 0) ? 0 : abval % scale_factors[i];
                        number /= scale_factors[i];
                        if (i > 0)
                                fract /= scale_factors[i - 1];
                        break;
                }
        }

        fract = (10 * fract + 512) / 1024;
        /* if the result would be >= 10, round main number */
        if (fract >= 10) {
                if (number >= 0)
                        number++;
                else
                        number--;
                fract = 0;
        } else if (fract < 0) {
                /* shouldn't happen */
                fract = 0;
        }

        if (number == 0)
                strlcpy(result, "0B", FMT_SCALED_STRSIZE);
        else if (unit == NONE || number >= 100 || number <= -100) {
                if (fract >= 5) {
                        if (number >= 0)
                                number++;
                        else
                                number--;
                }
                (void)snprintf(result, FMT_SCALED_STRSIZE, "%lld%c",
                        number, scale_chars[unit]);
        } else
                (void)snprintf(result, FMT_SCALED_STRSIZE, "%lld.%1lld%c",
                        number, fract, scale_chars[unit]);

        return 0;
}

#ifdef  MAIN
/*
 * This is the original version of the program in the man page.
 * Copy-and-paste whatever you need from it.
 */
int
main(int argc, char **argv)
{
        char *cinput = "1.5K", buf[FMT_SCALED_STRSIZE];
        long long ninput = 10483892, result;

        if (scan_scaled(cinput, &result) == 0)
                printf("\"%s\" -> %lld\n", cinput, result);
        else
                perror(cinput);

        if (fmt_scaled(ninput, buf) == 0)
                printf("%lld -> \"%s\"\n", ninput, buf);
        else
                fprintf(stderr, "%lld invalid (%s)\n", ninput, strerror(errno));

        return 0;
}
#endif