Module fragmentation 

Splits payloads larger than one crypto provider message into fragments and reassembles them on the receiving side.

Fragmentation runs above the CryptoProvider, so each fragment is an ordinary OutgoingMessage that the provider encrypts on its own. A fragment’s topic is the original topic behind the reserved FRAGMENT_TOPIC prefix, and its payload is a FragmentFrame: a CBOR FragmentHeader followed by the raw fragment data, so the data is copied once on each side. Peers without fragmentation support deliver such messages to subscribers as an unknown topic.

The sender awaits each fragment before sending the next and the communication backends deliver in order, so fragments are appended as they arrive and any gap discards the message.

Every peer is untrusted, so the Reassembler bounds the reassembled size, and the number of incomplete messages and the bytes reserved for them, both per source and per pool. Web pages are numerous and untrusted, so all web sources share a smaller pool that cannot consume the pool of the other sources. An incomplete message is discarded when no fragment arrives for REASSEMBLY_IDLE_TIMEOUT, or REASSEMBLY_TIMEOUT after its first fragment.

Modules

reassembler 🔒

split 🔒

Structs

FragmentFrame 🔒

Payload of a fragment message: the FragmentHeader in CBOR followed directly by the raw data, so the data is not re-encoded.

FragmentHeader 🔒

Metadata that identifies a fragment within its message.

Constants

FRAGMENT_TOPIC 🔒

Reserved topic that marks a message as a fragment. A fragment of a message with a topic carries IpcFragment/<topic>.

MAX_HEADER_LEN 🔒

Upper bound on the encoded size of a FragmentHeader.

MAX_PAYLOAD_SIZE 🔒

Largest payload that can be sent, and the largest reassembled payload a receiver accepts. IPC is meant for messages, so larger data has to be streamed some other way.

Type Aliases

OriginalTopic 🔒

Topic of the message a fragment belongs to, which may itself have no topic.