Serialization

How Bondy encodes and decodes values on the binary serializations, where a format distinguishes things that Bondy's internal representation does not, and what Bondy does with a message that does not decode. A client choosing MessagePack or CBOR needs every rule; a JSON client needs only the JSON and Payload Passthru Mode sections.

Text and bytes

MessagePack and CBOR each have two string types: a text string (MessagePack str, CBOR major type 3) and a byte string (MessagePack bin, CBOR major type 2). Bondy holds both as the same thing, a sequence of bytes, so when it encodes one it chooses the type from the content:

Value	MessagePack	CBOR
Valid UTF-8	str	text string
Not valid UTF-8	bin	byte string

This applies to every string Bondy writes: URIs, authentication methods, error messages, map keys, and payload values. The bondy_connect_sdk Erlang client encodes through the same rule.

On decode both types become the same value, so the distinction a client sent does not survive a round trip through Bondy's decoder. Bondy decodes every MessagePack message in full, so a MessagePack bin whose bytes happen to be valid UTF-8 reaches the other peer as a str. Send binary data that must stay binary in a form that is not valid UTF-8, or encode it (for example as Base64) inside a string.

MessagePack

• nil is Bondy's absent value, the same one a JSON null or a CBOR null decodes to. Bondy writes an absent value as nil.
• A map that repeats a key keeps the first value.
• Extension types (fixext, ext, including the timestamp extension) have no meaning in WAMP and are rejected. So is the reserved type 0xC1, and so is a truncated message or one with bytes after its end. When a message does not decode, Bondy aborts the session with wamp.error.protocol_violation.
• Integers use the smallest MessagePack type that holds the value. Floats are written as 64-bit; a 32-bit float is accepted on decode.

CBOR

• null and undefined both decode to Bondy's absent value. Bondy writes an absent value as null.
• A message that does not decode, such as a truncated message, one with bytes after its end, or an array whose declared length does not match its items, aborts the session with wamp.error.protocol_violation. Bondy checks that the payload of each message decodes when the message arrives, so a malformed payload aborts the sender and never reaches a receiver.

JSON

• A message that is not one JSON value, such as truncated text or text after the end of the value, aborts the session with wamp.error.protocol_violation. As for CBOR, Bondy checks that the payload of each message decodes when the message arrives.

WAMP Compliance lists the other messages Bondy refuses, whatever the serialization.

Payload Passthru Mode

A message carrying ppt_scheme has an opaque payload that Bondy routes without reading. Bondy's own procedures need to read their arguments, so a CALL with ppt_scheme to a procedure Bondy implements is refused with wamp.error.invalid_argument.

An ERROR that Bondy itself raises in reply to a Payload Passthru request, such as an authorization refusal, carries no ppt_* details: those describe a payload, and an error Bondy raises has none.