Module datagram 

HTTP Datagram payload coding (RFC 9297) and QUIC varints (RFC 9000 §16).

An HTTP/3 datagram carried in a QUIC DATAGRAM frame is:

Quarter Stream ID (varint) | Context ID (varint) | payload

The Quarter Stream ID is the request stream’s id divided by four (RFC 9297 §2.1) — not the stream id itself. Getting this wrong is the failure mode that makes every UDP session after the first on a connection misroute, which is exactly the h3-datagram 0.0.2 bug this crate avoids by encoding datagrams here instead. The unit tests below pin the relationship.

For CONNECT-UDP the Context ID is 0, meaning “the payload is a raw UDP datagram” (RFC 9298 §4).

Structs

Datagram

A decoded HTTP/3 datagram.

Enums

DecodeError

Why a datagram could not be decoded.

Constants

CONTEXT_ID_UDP_PAYLOAD

Context ID for an unmodified UDP payload (RFC 9298 §4).

MAX_QUARTER_STREAM_ID

Largest legal Quarter Stream ID (RFC 9297 §2.1).

MAX_UDP_PAYLOAD

Largest UDP payload that can be represented (RFC 9298 §5).

VARINT_MAX

Largest value a QUIC varint can hold (RFC 9000 §16).

Functions

decode

Decodes an HTTP/3 datagram, sharing the payload buffer rather than copying.

encode

Encodes an HTTP/3 datagram.

encode_udp_payload

Encodes a datagram for quarter_stream_id carrying a raw UDP payload.

encoded_len

The number of bytes encode will produce.

peek_varint

Decodes the varint at the start of buf, returning it and its byte length.

put_varint

Appends value as a QUIC varint.

quarter_stream_id

The Quarter Stream ID identifying the session on stream_id.

take_varint

Reads a QUIC varint from the front of buf, consuming it.

varint_len

Encoded length of value as a QUIC varint.