BGPLite/BGPLite.Tests/PrefixCodecTests.cs

using BGPLite.Protocol;

namespace BGPLite.Tests;

public class PrefixCodecTests
{
    [Fact]
    public void Encode_24bitPrefix_3bytes()
    {
        var prefix = new IpPrefix(0xC0A80000, 24); // 192.168.0.0/24
        var buffer = new byte[8];
        var written = PrefixCodec.Encode(prefix, buffer);

        Assert.Equal(4, written);
        Assert.Equal((byte)24, buffer[0]);
        Assert.Equal(0xC0, buffer[1]);
        Assert.Equal(0xA8, buffer[2]);
        Assert.Equal(0x00, buffer[3]);
    }

    [Fact]
    public void Encode_8bitPrefix_2bytes()
    {
        var prefix = new IpPrefix(0x0A000000, 8); // 10.0.0.0/8
        var buffer = new byte[8];
        var written = PrefixCodec.Encode(prefix, buffer);

        Assert.Equal(2, written);
        Assert.Equal((byte)8, buffer[0]);
        Assert.Equal(0x0A, buffer[1]);
    }

    [Fact]
    public void Encode_32bitPrefix_5bytes()
    {
        var prefix = new IpPrefix(0x01020304, 32); // 1.2.3.4/32
        var buffer = new byte[8];
        var written = PrefixCodec.Encode(prefix, buffer);

        Assert.Equal(5, written);
        Assert.Equal((byte)32, buffer[0]);
        Assert.Equal(0x01, buffer[1]);
        Assert.Equal(0x02, buffer[2]);
        Assert.Equal(0x03, buffer[3]);
        Assert.Equal(0x04, buffer[4]);
    }

    [Fact]
    public void Encode_DefaultRoute_1byte()
    {
        var prefix = new IpPrefix(0, 0); // 0.0.0.0/0
        var buffer = new byte[8];
        var written = PrefixCodec.Encode(prefix, buffer);

        Assert.Equal(1, written);
        Assert.Equal((byte)0, buffer[0]);
    }

    [Fact]
    public void Roundtrip_VariousPrefixes()
    {
        var prefixes = new[]
        {
            new IpPrefix(0xC0A80000, 24),
            new IpPrefix(0x0A000000, 8),
            new IpPrefix(0x01020304, 32),
            new IpPrefix(0, 0),
            new IpPrefix(0xAC100000, 20)
        };

        var buffer = new byte[64];
        var written = PrefixCodec.EncodeList(prefixes, buffer);

        var decoded = new IpPrefix[prefixes.Length];
        var count = PrefixCodec.DecodeList(buffer, written, decoded);

        Assert.Equal(prefixes.Length, count);
        for (var i = 0; i < count; i++)
        {
            Assert.Equal(prefixes[i].Address, decoded[i].Address);
            Assert.Equal(prefixes[i].Length, decoded[i].Length);
        }
    }
}