Python/conversions/ipv4_conversion.py

# https://www.geeksforgeeks.org/convert-ip-address-to-integer-and-vice-versa/


def ipv4_to_decimal(ipv4_address: str) -> int:
    """
    Convert an IPv4 address to its decimal representation.

    Args:
        ip_address: A string representing an IPv4 address (e.g., "192.168.0.1").

    Returns:
        int: The decimal representation of the IP address.

    >>> ipv4_to_decimal("192.168.0.1")
    3232235521
    >>> ipv4_to_decimal("10.0.0.255")
    167772415
    >>> ipv4_to_decimal("10.0.255")
    Traceback (most recent call last):
        ...
    ValueError: Invalid IPv4 address format
    >>> ipv4_to_decimal("10.0.0.256")
    Traceback (most recent call last):
        ...
    ValueError: Invalid IPv4 octet 256
    """

    octets = [int(octet) for octet in ipv4_address.split(".")]
    if len(octets) != 4:
        raise ValueError("Invalid IPv4 address format")

    decimal_ipv4 = 0
    for octet in octets:
        if not 0 <= octet <= 255:
            raise ValueError(f"Invalid IPv4 octet {octet}")  # noqa: EM102
        decimal_ipv4 = (decimal_ipv4 << 8) + int(octet)

    return decimal_ipv4


def alt_ipv4_to_decimal(ipv4_address: str) -> int:
    """
    >>> alt_ipv4_to_decimal("192.168.0.1")
    3232235521
    >>> alt_ipv4_to_decimal("10.0.0.255")
    167772415
    """
    return int("0x" + "".join(f"{int(i):02x}" for i in ipv4_address.split(".")), 16)


def decimal_to_ipv4(decimal_ipv4: int) -> str:
    """
    Convert a decimal representation of an IP address to its IPv4 format.

    Args:
        decimal_ipv4: An integer representing the decimal IP address.

    Returns:
        The IPv4 representation of the decimal IP address.

    >>> decimal_to_ipv4(3232235521)
    '192.168.0.1'
    >>> decimal_to_ipv4(167772415)
    '10.0.0.255'
    >>> decimal_to_ipv4(-1)
    Traceback (most recent call last):
        ...
    ValueError: Invalid decimal IPv4 address
    """

    if not (0 <= decimal_ipv4 <= 4294967295):
        raise ValueError("Invalid decimal IPv4 address")

    ip_parts = []
    for _ in range(4):
        ip_parts.append(str(decimal_ipv4 & 255))
        decimal_ipv4 >>= 8

    return ".".join(reversed(ip_parts))


if __name__ == "__main__":
    import doctest

    doctest.testmod()