#pragma once

#include <stdint.h>

struct ip_common {
    uint8_t version;
    uint8_t tc;
    uint8_t proto;
    uint8_t hdr_size;
    uint16_t size;
};

_pure_ static inline uint8_t
ip_get_version(const uint8_t *data, size_t size)
{
    if (size < 20)
        return 0;

    return data[0] >> 4;
}

static inline int
ip_get_common(struct ip_common *ic, const uint8_t *data, size_t size)
{
    ic->version = ip_get_version(data, size);

    switch (ic->version) {
    case 4:
        ic->tc = data[1];
        ic->proto = data[9];
        ic->hdr_size = (data[0] & 0xF) << 2;
        ic->size = ((data[2] << 8) | data[3]);
        if (ic->size >= 20)
            return 0;
        break;
    case 6:
        ic->tc = ((data[0] & 0xF) << 4) | (data[1] >> 4);
        ic->proto = data[6];
        ic->hdr_size = 40;
        ic->size = ((data[4] << 8) | data[5]) + 40;
        return 0;
    }

    return -1;
}