Module data_stream 

Draft-15 data stream header encoding and decoding.

Draft-15 data streams differ significantly from draft-14:

• Subgroup stream types encode flags in the type byte. Section 10.4.2 Table 6 assigns twenty-four: 0x10-0x15, 0x18-0x1D, 0x30-0x35 and 0x38-0x3D.
• Priority is absent when type & 0x20, and the object then inherits the priority the subscription established
• type & 0x06 decides how the Subgroup ID is carried: it is zero, it is the first object’s ID, or it is a field on the wire. Table 6 states that as two columns — Subgroup ID Field Present, and Subgroup ID Value — not as a mode field, and the fourth combination is simply not a row in it
• type & 0x08 marks a stream whose last object ends its group
• Extensions flag (type & 0x01) affects per-object parsing
• Fetch objects use serialization_flags for delta encoding
• Object IDs in subgroups use delta encoding (first=absolute, subsequent=delta+1)

Structs

DatagramHeader

Datagram header for draft-15.

FetchHeader

Fetch stream header for draft-15.

FetchObjectHeader

One object on a draft-15 fetch stream, without its payload.

FetchObjectReader

Stateful reader/writer for the objects on one draft-15 fetch stream.

FetchObjectWriter

Re-encodes resolved fetch Objects onto one FETCH stream.

PriorFetchObject 🔒

The fields a draft-15 fetch object leaves to its successor to inherit.

SubgroupHeader

Subgroup stream header for draft-15.

SubgroupObject

One object within a draft-15 subgroup stream with its Object ID already resolved from the delta encoding.

SubgroupObjectMeta

The framing of one draft-15 subgroup object, without its payload.

SubgroupObjectReader

Stateful reader/writer for draft-15 subgroup objects.

Enums

PayloadPermission

Whether an object carrying a given status may hold a non-empty payload.

SubgroupIdEncoding

How a draft-15 fetch object carries its Subgroup ID.

Constants

FETCH_STREAM_TYPE 🔒

The unidirectional stream type draft-15 Section 10.4.4 gives a fetch stream.

Functions

check_extensions_against_status_on_encode 🔒

Refuse an object that would be written with extension headers beside a status other than Normal.

datagram_type_is_assigned 🔒

Whether draft-15 Section 10.3.1 Table 5 assigns this datagram type.

decoded_status 🔒

Turn a wire Object Status code into the status draft-15 gives it, refusing any code the draft does not assign.

skip 🔒

Advance buf past len bytes without copying them.

stream_type_error 🔒

Which failure a leading unidirectional stream type that is not the one a reader wants is.

subgroup_type_is_assigned 🔒

Whether draft-15 Section 10.4.2 Table 6 assigns this subgroup stream type.