Encoder Implementation

Encoder picks smallest format:

Performance:

• Build via list of bytes objects + b''.join.
• Avoids quadratic concat.
• Modern Python: BytesIO also fine.

Roundtrip:

Custom types:

• Pre-encode hook: user provides function for non-built-in types.
• Most libs return ExtType for user-registered types.

Streaming encode:

• For huge maps/arrays: emit length, then stream items.
• Saves memory.