Serialization

We use postcard to serialize and deserialize messages. It’s a compact, serde-compatible binary format (a bool takes a single byte, integers use varint encoding).

When sending messages, we start by serializing the message early into a Bytes structure.

This allows us to:

• know the size of the message right away (which helps with packet fragmentation)
• cheaply copy the message if we need to send it multiple times (for reliable channels) However:
• it is much more expensive and inefficient to call serialize on each individual message compared with the final packet, and the serialized bytes compress less efficiently

Buffers

We use a Writer (backed by a reusable BytesMut allocation) to serialize messages, so we don’t allocate from scratch for every message.

When we receive a packet, we wrap the bytes in a Reader (a cursor over the shared Bytes, no copy) and deserialize messages from it in order.