/// <summary>
/// Writes a protocol-buffer representation of the given instance to the supplied stream,
/// with a length-prefix. This is useful for socket programming,
/// as DeserializeWithLengthPrefix/MergeWithLengthPrefix can be used to read the single object back
/// from an ongoing stream.
/// </summary>
/// <typeparam name="T">The type being serialized.</typeparam>
/// <param name="instance">The existing instance to be serialized (cannot be null).</param>
/// <param name="style">How to encode the length prefix.</param>
/// <param name="destination">The destination stream to write to.</param>
/// <param name="tag">The tag used as a prefix to each record (only used with base-128 style prefixes).</param>
public static void SerializeWithLengthPrefix <T>(Stream destination, T instance, PrefixStyle style, int tag)
{
if (style == PrefixStyle.None)
{
Serialize <T>(destination, instance);
return;
}
using (MemoryStream ms = new MemoryStream())
{
Serialize <T>(ms, instance);
byte[] tmp = new byte[20];
int len;
switch (style)
{
case PrefixStyle.Base128:
len = 0;
if (tag > 0)
{
uint prefix = GetFieldToken(tag, WireType.String);
len += SerializationContext.EncodeUInt32(prefix, tmp, 0);
}
len += SerializationContext.EncodeUInt32((uint)ms.Length, tmp, len);
break;
case PrefixStyle.Fixed32:
SerializationContext.EncodeUInt32Fixed((uint)ms.Length, tmp, 0);
len = 4;
break;
default:
throw new NotSupportedException("Invalid prefix style: " + style);
}
destination.Write(tmp, 0, len);
destination.Write(ms.GetBuffer(), 0, (int)ms.Length);
}
destination.Flush();
}