/// <summary>
/// Constructs a subnet from an IPv4 address and subnet mask.
/// </summary>
/// <param name="address">The IP address.</param>
/// <param name="subnetMask">The subnet mask.</param>
public NetworkCidr(IPAddress address, IPAddress subnetMask)
{
Covenant.Requires <ArgumentNullException>(address != null, nameof(address));
Covenant.Requires <ArgumentException>(address.AddressFamily == AddressFamily.InterNetwork, nameof(address));
Covenant.Requires <ArgumentNullException>(subnetMask != null, nameof(subnetMask));
Covenant.Requires <ArgumentException>(subnetMask.AddressFamily == AddressFamily.InterNetwork, nameof(subnetMask));
// Count the number of zero bits from the least significant bit to
// the first non-zero bit.
var mask = NetHelper.AddressToUint(subnetMask);
for (var position = 0; position < 32; position++)
{
if ((mask & (1 << position)) != 0)
{
// Ensure that the remaining mask bits are all ones.
for (int i = position + 1; i < 32; i++)
{
if ((mask & (1 << i)) == 0)
{
throw new ArgumentException($"Subnet mask [{subnetMask}] is not valid because it has zero bits in the prefix.");
}
}
Initialize(address, 32 - position);
return;
}
}
Initialize(address, 0);
}
/// <summary>
/// Initializes the instance.
/// </summary>
/// <param name="address">The IP address.</param>
/// <param name="prefixLength">The network prefix mask length in bits.</param>
private void Initialize(IPAddress address, int prefixLength)
{
PrefixLength = prefixLength;
var maskBits = new Bits(32);
for (int i = 0; i < prefixLength; i++)
{
maskBits[i] = true;
}
Mask = new IPAddress(maskBits.ToBytes());
Address = NetHelper.UintToAddress(NetHelper.AddressToUint(address) & NetHelper.AddressToUint(Mask));
}
/// <summary>
/// Determines whether this subnet overlaps another.
/// </summary>
/// <param name="subnet">The subnet being tested.</param>
/// <returns><c>true</c> if the subnets overlap.</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="subnet"/> is <c>null</c>.</exception>
public bool Overlaps(NetworkCidr subnet)
{
Covenant.Requires <ArgumentNullException>(subnet != null);
var first = NetHelper.AddressToUint(this.FirstAddress);
var last = NetHelper.AddressToUint(this.LastAddress);
var subnetFirst = NetHelper.AddressToUint(subnet.FirstAddress);
var subnetLast = NetHelper.AddressToUint(subnet.LastAddress);
if (last < subnetFirst)
{
return(false);
}
else if (first > subnetLast)
{
return(false);
}
else
{
return(true);
}
}