Class: shaka.msf.draft18.Session

Constructor

new Session(webTransportnon-null, controlWriternon-null, dialectnon-null, confignon-null, messageWriterFactory)

Parameters:
Name Type Description
webTransport WebTransport
controlWriter shaka.msf.Writer Our outgoing control stream, already carrying our SETUP.
dialect shaka.extern.MsfDialect
config shaka.extern.MsfManifestConfiguration
messageWriterFactory function Builds a writer for this draft's control messages.
Implements:
Source:

Members

END_OF_RANGE_ :Array<number>

The Serialization Flags values that mark an End of Range: Objects that do not exist, whose status is unknown, and (from draft-20) that timed out.
Type:
  • Array<number>
Source:

FetchFlags_ :number

The Serialization Flags of an Object on a fetch stream (draft-18 section 11.4.4.1; draft-20 and draft-21 are the same).
Type:
  • number
Properties:
Name Value Type Description
SUBGROUP_MASK 3 number
SUBGROUP_ZERO 0 number
SUBGROUP_PRIOR 1 number
SUBGROUP_PRIOR_PLUS_ONE 2 number
SUBGROUP_PRESENT 3 number
OBJECT_ID_DELTA 4 number
GROUP_ID_DELTA 8 number
PRIORITY 16 number
PROPERTIES 32 number
DATAGRAM 64 number
MAX 127 number
Source:

JOIN_TIMEOUT_SEC_ :number

How long a subscription that joins the current Group holds its own Objects back waiting for that Group, in seconds. Only a publisher that ignores the request runs into it.
Type:
  • number
Source:

LARGEST_OBJECT_ :number

The LARGEST_OBJECT Message Parameter type.
Type:
  • number
Source:

LOCATION_FILTER_FIELDS_ :Map<number, number>

How many var ints follow each draft-22 Location Filter Type (draft-22 section 9.20.9): none for None (0x00) and Next Object (0x05), and for the rest as many as the type's own value.
Type:
  • Map<number, number>
Source:

config_ :shaka.extern.MsfManifestConfiguration

Type:
Source:

controlWriter_ :shaka.msf.Writer

Type:
Source:

dialect_ :shaka.extern.MsfDialect

Type:
Source:

fetches_ :Map<bigint, shaka.msf.draft18.Session.PendingFetch>

The fetches in flight, by request ID. `accepted` settles once the FETCH_OK or REQUEST_ERROR arrives: a publisher may start sending Objects before it answers, and they are held until then, because the Track Properties that say how to read them are in the FETCH_OK.
Type:
Source:

isClosing_ :boolean

Type:
  • boolean
Source:

joinGates_ :Map<bigint, !shaka.msf.JoinGate>

What puts the Objects of a subscription that joins the current Group in order, by track alias, until the subscription goes.
Type:
Source:

joiningFetches_ :Map<bigint, bigint>

The Request ID of the Joining FETCH sent for a subscription, by track alias, so that withdrawing the subscription withdraws it too.
Type:
  • Map<bigint, bigint>
Source:

messageWriterFactory_ :function(): !shaka.msf.draft18.MessageWriter

Type:
  • function(): !shaka.msf.draft18.MessageWriter
Source:

nextRequestId_ :bigint

Type:
  • bigint
Source:

parameterFormat_ :shaka.msf.draft18.MessageWriter

Kept only to ask how this draft encodes each Message Parameter, which the message layer owns because draft-22 changed one of them.
Type:
Source:

publishNamespaceCallbacks_ :Set<function(Array<string>)>

Type:
  • Set<function(Array<string>)>
Source:

subscribeStreams_ :Map<bigint, {reader: !shaka.msf.Reader, writer: !shaka.msf.Writer}>

The request stream each subscription lives on, by track alias. The stream IS the subscription, so it is what has to be torn down to withdraw one.
Type:
Source:

trackProperties_ :Map<bigint, !Uint8Array>

The Track Properties of each subscription's SUBSCRIBE_OK, by track alias, for subscriptions that had any.
Type:
  • Map<bigint, !Uint8Array>
Source:

trackRegistry_ :shaka.msf.TrackAliasRegistry

Type:
Source:

webTransport_ :WebTransport

Type:
  • WebTransport
Source:

Methods

awaitResponse_(readernon-null, okType, description) → {Promise<{type: number, length: number}>}

Waits for the response to a request, which is either a REQUEST_OK-shaped acknowledgement or a REQUEST_ERROR.
Parameters:
Name Type Description
reader shaka.msf.Reader
okType number The success message type for this request.
description string Used in error messages.
Source:
Returns:
The response header. The reader is left positioned just after it.
Type
Promise<{type: number, length: number}>

buildSubscribeParams_(writernon-null, startLocationopt, nullable) → {Array<shaka.msf.Utils.KeyValuePair>}

Builds the parameter list carried by SUBSCRIBE. Draft-16 moved the subscriber priority, forward flag, filter and group order out of fixed fields into parameters, and draft-18 keeps them there. Every one of them has a default, so the shortest legal list is the empty one.
Parameters:
Name Type Attributes Description
writer shaka.msf.draft18.MessageWriter The writer this SUBSCRIBE is going out on, which owns how a start Location is encoded.
startLocation shaka.msf.Utils.Location <optional>
<nullable>
Source:
Returns:
Type
Array<shaka.msf.Utils.KeyValuePair>

close(codeopt, reasonopt) → {Promise}

Closes the underlying transport.
Parameters:
Name Type Attributes Description
code number <optional>
reason string <optional>
Implements:
Source:
Returns:
Type
Promise

configure(confignon-null)

Parameters:
Name Type Description
config shaka.extern.MsfManifestConfiguration
Implements:
Source:

deliver_(trackAlias, obj) → {Promise}

Delivers an object, waiting briefly for the subscription to be registered if the data stream beat the SUBSCRIBE_OK.
Parameters:
Name Type Description
trackAlias bigint
obj shaka.msf.Utils.MOQObject
Source:
Returns:
Type
Promise

fetch(namespace, trackName, callback) → {Promise}

Retrieves a track once rather than subscribing to it. Resolves when the request has been accepted; objects arrive on the callback.
Parameters:
Name Type Description
namespace Array<string>
trackName string
callback shaka.extern.MsfObjectCallback
Implements:
Source:
Returns:
Type
Promise

forgetFetch_(requestId)

Stops handing on the Objects of a fetch, including the ones of a stream that is already being read.
Parameters:
Name Type Description
requestId bigint
Source:

getNextRequestId_() → {bigint}

Client Request IDs are even and start at 0.
Source:
Returns:
Type
bigint

handleFetchStream_(readernon-null) → {Promise}

Reads a fetch stream: a FETCH_HEADER naming the request, then Objects until the stream ends. The request is a FETCH, or a SUBSCRIBE whose FILL_PARAMETERS asked for Groups already published.
Parameters:
Name Type Description
reader shaka.msf.Reader
Source:
Returns:
Type
Promise

handleIncomingStream_(streamnon-null) → {Promise}

Parameters:
Name Type Description
stream ReadableStream
Source:
Returns:
Type
Promise

handlePeerControlStream_(readernon-null) → {Promise}

Reads the peer's SETUP and then keeps the control stream open for GOAWAY and namespace announcements.
Parameters:
Name Type Description
reader shaka.msf.Reader Positioned just after the SETUP type.
Source:
Returns:
Type
Promise

handleSubgroupStream_(readernon-null, streamType) → {Promise}

Parameters:
Name Type Description
reader shaka.msf.Reader
streamType bigint
Source:
Returns:
Type
Promise

isSubgroupStreamType_(streamType) → {boolean}

Draft-18 SUBGROUP_HEADER types have bit 4 set, spanning 0x10-0x1F, 0x30-0x3F, 0x50-0x5F and 0x70-0x7F.
Parameters:
Name Type Description
streamType bigint
Source:
Returns:
Type
boolean

joinSubscription_(subscribeRequestId, trackAlias, gatenon-null, description) → {Promise}

Sends the Joining FETCH that delivers a subscription's current Group from its first Object, which the subscription itself starts after. Nothing waits on it. It fails when nothing has been published on the track yet, and then the subscription delivers everything there is.
Parameters:
Name Type Description
subscribeRequestId bigint
trackAlias bigint
gate shaka.msf.JoinGate
description string
Source:
Returns:
Type
Promise

listenOnRequestStream_(readernon-null, trackAlias) → {Promise}

Keeps reading a subscription's request stream after the SUBSCRIBE_OK so that PUBLISH_DONE closes the track.
Parameters:
Name Type Description
reader shaka.msf.Reader
trackAlias bigint
Source:
Returns:
Type
Promise

logStreamFailure_(context, error)

Streams end for reasons that are not a failure of ours: the peer resets one it no longer needs, and every stream on a session fails at once when the session goes away, which the session itself already reports. Neither is worth an error in the log.
Parameters:
Name Type Description
context string
error *
Source:

onNamespacePublished(callback) → {function}

Registers a callback for namespaces the peer announces it can serve.
Parameters:
Name Type Description
callback function
Implements:
Source:
Returns:
Unregisters the callback.
Type
function

openRequest_(requestBytesnon-null) → {Promise<{reader: !shaka.msf.Reader, writer: !shaka.msf.Writer}>}

Opens a bidirectional stream, writes a request onto it and returns both halves: the reader the response arrives on, and the writer, which is kept only so the stream can be torn down to withdraw the request. The stream is the correlation, so nothing is registered anywhere.
Parameters:
Name Type Description
requestBytes Uint8Array
Source:
Returns:
Type
Promise<{reader: !shaka.msf.Reader, writer: !shaka.msf.Writer}>

readFetchObjects_(readernon-null, requestId, pending) → {Promise}

Reads the Objects of a fetch stream, past its FETCH_HEADER, and hands them to the fetch's callback until the stream ends or the fetch is withdrawn.
Parameters:
Name Type Description
reader shaka.msf.Reader
requestId bigint
pending shaka.msf.draft18.Session.PendingFetch
Source:
Returns:
Type
Promise

readMessageHeader_(readernon-null) → {Promise<{type: number, length: number}>}

Reads one control message header from a stream.
Parameters:
Name Type Description
reader shaka.msf.Reader
Source:
Returns:
Type
Promise<{type: number, length: number}>

readResponseTail_(payloadnon-null, offset, leadingVarInts, description) → {shaka.msf.draft18.Session.ResponseTail}

Finds the Track Properties at the end of a SUBSCRIBE_OK or FETCH_OK payload, and the LARGEST_OBJECT parameter on the way. The Track Properties run to the end of the message with no length of their own, so they start wherever the Parameters before them end. Parameters are the obstacle: since draft-18 a Parameter's value is encoded however its type says, rather than by the parity rule Properties use, so an unknown type cannot be stepped over. Only EXPIRES and LARGEST_OBJECT may appear in these two responses at all; the others the message layer knows are stepped over too so that a lenient publisher costs us nothing.
Parameters:
Name Type Description
payload Uint8Array
offset number Where the fields still to be read begin.
leadingVarInts number How many var int fields sit between the offset and the Number of Parameters field.
description string Used in log messages.
Source:
Returns:
Type
shaka.msf.draft18.Session.ResponseTail

readRest_(readernon-null, header, bytesConsumed) → {Promise<!Uint8Array>}

Reads whatever is left of a message payload the caller stopped reading part way through.
Parameters:
Name Type Description
reader shaka.msf.Reader
header {type: number, length: number}
bytesConsumed number
Source:
Returns:
Type
Promise<!Uint8Array>

release()

Request that this object release all internal references.
Inherited From:
Implements:
Source:

sendFetch_(requestBytesnon-null, requestId, callback, description, onEndopt, nullable) → {Promise}

Sends a FETCH and waits for its answer. The Objects arrive on a stream of their own, which handleFetchStream_ hands to the callback.
Parameters:
Name Type Attributes Description
requestBytes Uint8Array
requestId bigint
callback shaka.msf.Utils.ObjectCallback
description string
onEnd ?function()= <optional>
<nullable>
 Called once no more Objects will be handed to the callback.
Source:
Returns:
Type
Promise

startListeningForStreams_() → {Promise}

Reads incoming unidirectional streams. Each is either the peer's control stream, which begins with SETUP, or object data.
Source:
Returns:
Type
Promise

subscribe(namespace, trackName, callback, startLocationopt, nullable, joinCurrentGroupopt) → {Promise<bigint>}

Subscribes to a track, delivering its objects to the callback until unsubscribed. Resolves with the track alias assigned by the publisher.
Parameters:
Name Type Attributes Description
namespace Array<string>
trackName string
callback shaka.extern.MsfObjectCallback
startLocation shaka.extern.MsfLocation <optional>
<nullable>
 Where delivery should begin, for a subscription that is not meant to start at the live edge, which is what a seek into published-but-not-yet-received content needs. Every draft carries it, though not alike: draft-18 in the SUBSCRIPTION_FILTER parameter, draft-20 in LOCATION_FILTER. A publisher may still refuse it, in which case the subscription fails rather than silently starting somewhere else.
joinCurrentGroup boolean <optional>
 Also deliver the Group the live edge is in from its first Object, rather than only what comes after the subscription starts. MSF requires it of the catalog, whose current state is the first Object of the latest Group plus the ones after it. Draft-18 does it with a Joining FETCH and draft-20 with FILL_PARAMETERS; the Objects arrive on the same callback as the subscription's, in Location order and without repeats. A session that cannot do it, or whose publisher does not answer in time, delivers only what the subscription does.
Implements:
Source:
Returns:
Type
Promise<bigint>

unsubscribe(trackAlias) → {Promise}

Stops delivery for a subscription.
Parameters:
Name Type Description
trackAlias bigint
Implements:
Source:
Returns:
Type
Promise

watchForSessionEnd_()

A session the peer hangs up on resets every stream on it at once, and each of those failures would otherwise be logged as an error of its own. Watch the transport instead: once the session is gone, its stream errors are expected, and the reason the session ended is the one worth reporting.
Source:

Type Definitions

PendingFetch

Type:
Properties:
Name Type Attributes Description
callback shaka.msf.Utils.ObjectCallback Receives the fetched Objects.
accepted Promise.PromiseWithResolvers<boolean> Resolves with true on FETCH_OK and with false when the fetch fails or the session is released. It never rejects, so nothing waiting on it can leave a rejection unhandled.
trackProperties Uint8Array <nullable>
 The Track Properties of the FETCH_OK, once it has arrived.
onEnd function <nullable>
 Called once no more Objects will be handed to the callback: the fetch stream has ended or failed, or the fetch has been refused or withdrawn.
Source:

ResponseTail

Type:
Properties:
Name Type Attributes Description
largestObject shaka.msf.Utils.Location | undefined The LARGEST_OBJECT parameter; null when the response has none, which means nothing has been published on the track, and undefined when the parameters could not be read.
trackProperties Uint8Array <nullable>
 The Track Properties block, or null when it is empty or cannot be located.
Source: