numbers

/*
 * numbers.c - number formatting library
 * Copyright (C) 2019 Matteo Croce <mcroce@redhat.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#define human(x) decimals(x), rounded(x), suffix(x)
#define H ".*f %s"

static double rounded(uint64_t n)
{
    if (n >= 9999500000)
        return n / 1000000000.0;
    if (n >= 9999500)
        return n / 1000000.0;
    if (n > 9999)
        return n / 1000.0;
    return n;
}

static int decimals(uint64_t n)
{
    if (n >= 999950000000)
        return 0;
    if (n >= 99995000000)
        return 1;
    if (n >= 9999500000)
        return 2;
    if (n >= 999950000)
        return 0;
    if (n >= 99995000)
        return 1;
    if (n >= 9999500)
        return 2;
    if (n >= 999950)
        return 0;
    if (n >= 99995)
        return 1;
    if (n > 9999)
        return 2;
    return 0;
}

static char* suffix(uint64_t n)
{
    if (n >= 9999500000)
        return "G";
    if (n >= 9999500)
        return "M";
    if (n > 9999)
        return "K";
    return "";
}

void removeDots(char *s) {
    int i, j, n = strlen(s);
    for (i=j=0; i < n; i++)
        if (s[i] != '.')
            s[j++] = s[i];
    s[j] = 0;
}

static char nums[][16] = {
    "9.999",
    "10.000",
    "99.994",
    "99.995",
    "999.949",
    "999.950",
    "9.999.499",
    "9.999.500",
    "99.994.999",
    "99.995.000",
    "999.949.999",
    "999.950.000",
    "9.999.499.999",
    "9.999.500.000",
    "99.994.999.999",
    "99.995.000.000",
    "999.949.999.999",
    "999.950.000.000",
};

int main(void)
{
    uint64_t n;
    int i;

    for(i = 0; i < sizeof(nums) / sizeof(*nums); i++) {
        printf("%15s => ", nums[i]);
        removeDots(nums[i]);
        n = atol(nums[i]);
        printf("%"H"\n", human(n));
    }

    return 0;
}