binary_prefix.c

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>


typedef enum BinaryPrefix {
    BINARY_PREFIX_NONE = 0, // × 1024°
    BINARY_PREFIX_KIBI,     // × 1024¹
    BINARY_PREFIX_MEBI,     // × 1024²
    BINARY_PREFIX_GIBI,     // × 1024³
    BINARY_PREFIX_TEBI,     // × 1024⁴
    BINARY_PREFIX_PEBI,     // × 1024⁵
    BINARY_PREFIX_EXBI,     // × 1024⁶
    BINARY_PREFIX_ZEBI,     // × 1024⁷
    BINARY_PREFIX_YOBI,     // × 1024⁸
} BinaryPrefix;

typedef struct DataUnit {
    double units;
    BinaryPrefix prefix;
} DataUnit;

DataUnit bytes_to_prefixed_data_units(size_t bytes) {
    DataUnit result = {
        .units = bytes,
        .prefix = BINARY_PREFIX_NONE,
    };
    while (result.units >= 1024.0 && result.prefix < BINARY_PREFIX_YOBI) {
        result.units /= 1024.0;
        result.prefix++;
    }
    return result;
}

const char* unit_prefix(BinaryPrefix prefix) {
    switch(prefix) {
    case BINARY_PREFIX_NONE:
        return "B";
    case BINARY_PREFIX_KIBI:
        return "KiB";
    case BINARY_PREFIX_MEBI:
        return "MiB";
    case BINARY_PREFIX_GIBI:
        return "GiB";
    case BINARY_PREFIX_TEBI:
        return "TiB";
    case BINARY_PREFIX_PEBI:
        return "PiB";
    case BINARY_PREFIX_EXBI:
        return "EiB";
    case BINARY_PREFIX_ZEBI:
        return "ZiB";
    case BINARY_PREFIX_YOBI:
        return "YiB";
    default:
        return "<unknown unit>";
    }
}

void data_unit_to_string(
    DataUnit data_unit,
    char* output_string,
    size_t length
) {
    snprintf(
        output_string,
        length,
        "%f%s",
        data_unit.units,
        unit_prefix(data_unit.prefix)
    );
}

void bytes_to_binary_prefix_string(
    size_t bytes,
    char* output_string,
    size_t length
) {
    data_unit_to_string(
        bytes_to_prefixed_data_units(bytes),
        output_string,
        length
    );
}

int main(void) {
    char buffer[256];
    // z = x^y
    size_t x = 15;
    size_t y = 5;

    size_t z = 1;
    for (size_t i = 0; i < y; i++) {
        z *= x;
    }
    bytes_to_binary_prefix_string(z, buffer, sizeof(buffer));
    printf("%s (%zu)\n", buffer, z);
}