Started adding ETF support

src/Discord.Net/API/Client/ETFEncoder.cs

@@ -0,0 +1,132 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Discord.API.Client
+{
+    //TODO: Floats, Atoms, Tuples, Lists, Dictionaries
+
+    public class ETFEncoder
+    {
+        private const byte SMALL_INTEGER_EXT = 97;
+        private const byte INTEGER_EXT = 98;
+        private const byte SMALL_BIG_EXT = 110;
+        private const byte SMALL_ATOM_EXT = 115;
+
+        private readonly static byte[] nilBytes = new byte[] { SMALL_ATOM_EXT, 3, (byte)'n', (byte)'i', (byte)'l' };
+        private readonly static byte[] falseBytes = new byte[] { SMALL_ATOM_EXT, 5, (byte)'f', (byte)'a', (byte)'l', (byte)'s', (byte)'e' };
+        private readonly static byte[] trueBytes = new byte[] { SMALL_ATOM_EXT, 4, (byte)'t', (byte)'r', (byte)'u', (byte)'e' };
+
+        private void WriteNil(BinaryWriter writer) => Append(writer, nilBytes);
+        public void Write(BinaryWriter writer, bool value) => Append(writer, value ? trueBytes : falseBytes);
+
+        public void Write(BinaryWriter writer, byte value) => Write(writer, (ulong)value);
+        public void Write(BinaryWriter writer, sbyte value) => Write(writer, (long)value);
+        public void Write(BinaryWriter writer, ushort value) => Write(writer, (ulong)value);
+        public void Write(BinaryWriter writer, short value) => Write(writer, (long)value);
+        public void Write(BinaryWriter writer, uint value) => Write(writer, (ulong)value);
+        public void Write(BinaryWriter writer, int value) => Write(writer, (long)value);
+        public void Write(BinaryWriter writer, ulong value)
+        {
+            if (value <= byte.MaxValue)
+                Append(writer, new byte[] { SMALL_INTEGER_EXT, (byte)value });
+            else if (value <= int.MaxValue)
+            {
+                Append(writer, new byte[] 
+                {
+                    INTEGER_EXT,
+                    (byte)((value >> 24) & 0xFF),
+                    (byte)((value >> 16) & 0xFF),
+                    (byte)((value >> 8) & 0xFF),
+                    (byte)(value & 0xFF)
+                });
+            }
+            else
+            {
+                var buffer = new byte[3 + 8];
+                buffer[0] = SMALL_BIG_EXT;
+                //buffer[1] = 0; //Always positive
+
+                byte bytes = 0;
+                while (value > 0)
+                {
+                    buffer[3 + bytes] = (byte)(value & 0xFF);
+                    value >>= 8;
+                    bytes++;
+                }
+                buffer[1] = bytes; //Encoded bytes
+
+                Append(writer, buffer, 3 + bytes);
+            }
+        }
+        public void Write(BinaryWriter writer, long value)
+        {
+            if (value >= byte.MinValue && value <= byte.MaxValue)
+                Append(writer, new byte[] { SMALL_INTEGER_EXT, (byte)value });
+            else if (value >= int.MinValue && value <= int.MaxValue)
+            {
+                Append(writer, new byte[]
+                {
+                    INTEGER_EXT,
+                    (byte)((value >> 24) & 0xFF),
+                    (byte)((value >> 16) & 0xFF),
+                    (byte)((value >> 8) & 0xFF),
+                    (byte)(value & 0xFF)
+                });
+            }
+            else
+            {
+                var buffer = new byte[3 + 8];
+                buffer[0] = SMALL_BIG_EXT;
+                if (value < 0)
+                {
+                    buffer[2] = 1; //Is negative
+                    value = -value;
+                }
+
+                byte bytes = 0;
+                while (value > 0)
+                {
+                    buffer[3 + bytes] = (byte)(value & 0xFF);
+                    value >>= 8;
+                    bytes++;
+                }
+                buffer[1] = bytes; //Encoded bytes
+
+                Append(writer, buffer, 3 + bytes);
+            }
+        }
+        
+        //public void Write(BinaryWriter writer, double value) => Write(writer, (float)value);
+        public void Write(BinaryWriter writer, float value)
+        {
+            throw new NotImplementedException();
+        }
+        
+        public void Write(BinaryWriter writer, byte[] value)
+        {
+            throw new NotImplementedException();
+        }
+        public void Write(BinaryWriter writer, string value)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Write<T>(BinaryWriter writer, T value)
+            where T : ISerializable
+        {
+            throw new NotImplementedException();
+        }
+        public void Write<T>(BinaryWriter writer, IEnumerable<T> value)
+            where T : ISerializable
+        {
+            throw new NotImplementedException();
+        }
+
+        private void Append(BinaryWriter writer, byte[] data) => Append(writer, data, data.Length);
+        private void Append(BinaryWriter writer, byte[] data, int length)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

src/Discord.Net/API/Client/ISerializable.cs

@@ -0,0 +1,9 @@
+using System.IO;
+
+namespace Discord.API.Client
+{
+    public interface ISerializable
+    {
+        void Write(BinaryWriter writer);
+    }
+}