mango/util/data_size.c

#include <stddef.h>
#include <mango/libc/stdio.h>

struct magnitude {
    size_t threshold;
    const char *suffix;
};

#define USE_BASE2

/* This list must be in decending order of threshold */
#ifdef USE_BASE2
static struct magnitude k_magnitudes[] = {
    { 0x10000000000, "TiB" },
    { 0x40000000, "GiB" },
    { 0x100000, "MiB" },
    { 0x400, "KiB" },
    { 0x00, "B" },
};
#else
static struct magnitude k_magnitudes[] = {
    { 1000000000000, "TB" },
    { 1000000000, "GB" },
    { 1000000, "MB" },
    { 1000, "KB" },
    { 0, "B" },
};
#endif

static void convert(size_t *big, size_t *small, size_t val, size_t threshold)
{
    if (!threshold) {
        *big = val;
        *small = 0;
        return;
    }

    *big = val / threshold;
    size_t rem = val % threshold;
    *small = (10 * rem) / threshold;
}

void data_size_to_string(size_t value, char *out, size_t outsz)
{
    if (!value) {
        snprintf(out, outsz, "0 B");
        return;
    }

    size_t def_count = sizeof(k_magnitudes) / sizeof(struct magnitude);

    for (size_t i = 0; i < def_count; i++) {
        if (value >= k_magnitudes[i].threshold) {
            size_t big, small;
            convert(&big, &small, value, k_magnitudes[i].threshold);
            if (small) {
                snprintf(out, outsz, "%zu.%zu %s", big, small, k_magnitudes[i].suffix);
            } else {
                snprintf(out, outsz, "%zu %s", big, k_magnitudes[i].suffix);
            }
            return;
        }
    }

    *out = 0;
}