/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.media.SegmentPrefetch');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.media.InitSegmentReference');
goog.require('shaka.media.SegmentReference');
goog.require('shaka.net.NetworkingEngine');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* @summary
* This class manages segment prefetch operations.
* Called by StreamingEngine to prefetch next N segments
* ahead of playhead, to reduce the chances of rebuffering.
*/
shaka.media.SegmentPrefetch = class {
/**
* @param {number} prefetchLimit
* @param {shaka.extern.Stream} stream
* @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
*/
constructor(prefetchLimit, stream, fetchDispatcher) {
/** @private {number} */
this.prefetchLimit_ = prefetchLimit;
/** @private {shaka.extern.Stream} */
this.stream_ = stream;
/** @private {number} */
this.prefetchPosTime_ = 0;
/** @private {shaka.media.SegmentPrefetch.FetchDispatcher} */
this.fetchDispatcher_ = fetchDispatcher;
/**
* @private {!Map.<
* !(shaka.media.SegmentReference),
* !shaka.media.SegmentPrefetchOperation>}
*/
this.segmentPrefetchMap_ = new Map();
/**
* @private {!Map.<
* !(shaka.media.InitSegmentReference),
* !shaka.media.SegmentPrefetchOperation>}
*/
this.initSegmentPrefetchMap_ = new Map();
}
/**
* @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
*/
replaceFetchDispatcher(fetchDispatcher) {
this.fetchDispatcher_ = fetchDispatcher;
for (const operation of this.segmentPrefetchMap_.values()) {
operation.replaceFetchDispatcher(fetchDispatcher);
}
}
/**
* @return {number}
*/
getLastKnownPosition() {
return this.prefetchPosTime_;
}
/**
* Fetch next segments ahead of current time.
*
* @param {number} currTime
* @param {boolean=} skipFirst
* @public
*/
prefetchSegmentsByTime(currTime, skipFirst = false) {
goog.asserts.assert(this.prefetchLimit_ > 0,
'SegmentPrefetch can not be used when prefetchLimit <= 0.');
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
if (!this.stream_.segmentIndex) {
shaka.log.debug(logPrefix, 'missing segmentIndex');
return;
}
const maxTime = Math.max(currTime, this.prefetchPosTime_);
const iterator = this.stream_.segmentIndex.getIteratorForTime(
maxTime, /* allowNonIndepedent= */ true);
if (!iterator) {
return;
}
let reference = iterator.next().value;
if (skipFirst) {
reference = iterator.next().value;
}
if (!reference) {
return;
}
while (this.segmentPrefetchMap_.size < this.prefetchLimit_ &&
reference != null) {
// By default doesn't prefech preload partial segments when using
// byterange
let prefetchAllowed = true;
if (reference.isPreload() && reference.endByte != null) {
prefetchAllowed = false;
}
if (reference.getStatus() ==
shaka.media.SegmentReference.Status.MISSING) {
prefetchAllowed = false;
}
if (prefetchAllowed && reference.initSegmentReference) {
this.prefetchInitSegment(reference.initSegmentReference);
}
if (prefetchAllowed && !this.segmentPrefetchMap_.has(reference)) {
const segmentPrefetchOperation =
new shaka.media.SegmentPrefetchOperation(this.fetchDispatcher_);
segmentPrefetchOperation.dispatchFetch(reference, this.stream_);
this.segmentPrefetchMap_.set(reference, segmentPrefetchOperation);
}
this.prefetchPosTime_ = reference.startTime;
if (this.stream_.fastSwitching && reference.isPartial() &&
reference.isLastPartial()) {
break;
}
reference = iterator.next().value;
}
this.clearInitSegments_();
}
/**
* Fetch init segment.
*
* @param {!shaka.media.InitSegmentReference} initSegmentReference
*/
prefetchInitSegment(initSegmentReference) {
goog.asserts.assert(this.prefetchLimit_ > 0,
'SegmentPrefetch can not be used when prefetchLimit <= 0.');
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
if (!this.stream_.segmentIndex) {
shaka.log.debug(logPrefix, 'missing segmentIndex');
return;
}
// init segments are ignored from the prefetch limit
const initSegments = Array.from(this.initSegmentPrefetchMap_.keys());
const someReference = initSegments.some((reference) => {
return shaka.media.InitSegmentReference.equal(
reference, initSegmentReference);
});
if (!someReference) {
const segmentPrefetchOperation =
new shaka.media.SegmentPrefetchOperation(this.fetchDispatcher_);
segmentPrefetchOperation.dispatchFetch(
initSegmentReference, this.stream_);
this.initSegmentPrefetchMap_.set(
initSegmentReference, segmentPrefetchOperation);
}
}
/**
* Get the result of prefetched segment if already exists.
* @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
* reference
* @param {?function(BufferSource):!Promise=} streamDataCallback
* @return {?shaka.net.NetworkingEngine.PendingRequest} op
* @public
*/
getPrefetchedSegment(reference, streamDataCallback) {
goog.asserts.assert(this.prefetchLimit_ > 0,
'SegmentPrefetch can not be used when prefetchLimit <= 0.');
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
let prefetchMap = this.segmentPrefetchMap_;
if (reference instanceof shaka.media.InitSegmentReference) {
prefetchMap = this.initSegmentPrefetchMap_;
}
if (prefetchMap.has(reference)) {
const segmentPrefetchOperation = prefetchMap.get(reference);
if (streamDataCallback) {
segmentPrefetchOperation.setStreamDataCallback(streamDataCallback);
}
if (reference instanceof shaka.media.SegmentReference) {
shaka.log.debug(
logPrefix,
'reused prefetched segment at time:', reference.startTime,
'mapSize', prefetchMap.size);
} else {
shaka.log.debug(
logPrefix,
'reused prefetched init segment at time, mapSize',
prefetchMap.size);
}
return segmentPrefetchOperation.getOperation();
} else {
if (reference instanceof shaka.media.SegmentReference) {
shaka.log.debug(
logPrefix,
'missed segment at time:', reference.startTime,
'mapSize', prefetchMap.size);
} else {
shaka.log.debug(
logPrefix,
'missed init segment at time, mapSize',
prefetchMap.size);
}
return null;
}
}
/**
* Clear All Helper
* @private
*/
clearMap_(map) {
for (const reference of map.keys()) {
if (reference) {
this.abortPrefetchedSegment_(reference);
}
}
}
/**
* Clear all segment data.
* @public
*/
clearAll() {
this.clearMap_(this.segmentPrefetchMap_);
this.clearMap_(this.initSegmentPrefetchMap_);
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
shaka.log.debug(logPrefix, 'cleared all');
this.prefetchPosTime_ = 0;
}
/**
* Remove a reference of prefetched segment if already exists.
* @param {!shaka.media.SegmentReference} reference
* @public
*/
removeReference(reference) {
this.abortPrefetchedSegment_(reference);
}
/**
* @param {number} time
* @param {boolean=} clearInitSegments
*/
evict(time, clearInitSegments = false) {
for (const ref of this.segmentPrefetchMap_.keys()) {
if (time > ref.endTime) {
this.abortPrefetchedSegment_(ref);
}
}
if (clearInitSegments) {
this.clearInitSegments_();
}
}
/**
* Remove all init segments that don't have associated segments in
* the segment prefetch map.
* By default, with delete on get, the init segments should get removed as
* they are used. With deleteOnGet set to false, we need to clear them
* every so often once the segments that are associated with each init segment
* is no longer prefetched.
* @private
*/
clearInitSegments_() {
const segmentReferences = Array.from(this.segmentPrefetchMap_.keys());
for (const initSegmentReference of this.initSegmentPrefetchMap_.keys()) {
// if no segment references this init segment, we should remove it.
const someReference = segmentReferences.some((segmentReference) => {
return shaka.media.InitSegmentReference.equal(
segmentReference.initSegmentReference, initSegmentReference);
});
if (!someReference) {
this.abortPrefetchedSegment_(initSegmentReference);
}
}
}
/**
* Reset the prefetchLimit and clear all internal states.
* Called by StreamingEngine when configure() was called.
* @param {number} newPrefetchLimit
* @public
*/
resetLimit(newPrefetchLimit) {
goog.asserts.assert(newPrefetchLimit >= 0,
'The new prefetch limit must be >= 0.');
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
shaka.log.debug(logPrefix, 'resetting prefetch limit to', newPrefetchLimit);
this.prefetchLimit_ = newPrefetchLimit;
const keyArr = Array.from(this.segmentPrefetchMap_.keys());
while (keyArr.length > newPrefetchLimit) {
const reference = keyArr.pop();
if (reference) {
this.abortPrefetchedSegment_(reference);
}
}
this.clearInitSegments_();
}
/**
* Called by Streaming Engine when switching variant.
* @param {shaka.extern.Stream} stream
* @public
*/
switchStream(stream) {
if (stream && stream !== this.stream_) {
this.clearAll();
this.stream_ = stream;
}
}
/**
* Get the current stream.
* @public
* @return {shaka.extern.Stream}
*/
getStream() {
return this.stream_;
}
/**
* Remove a segment from prefetch map and abort it.
* @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
* reference
* @private
*/
abortPrefetchedSegment_(reference) {
const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
let prefetchMap = this.segmentPrefetchMap_;
if (reference instanceof shaka.media.InitSegmentReference) {
prefetchMap = this.initSegmentPrefetchMap_;
}
const segmentPrefetchOperation = prefetchMap.get(reference);
prefetchMap.delete(reference);
if (segmentPrefetchOperation) {
segmentPrefetchOperation.abort();
if (reference instanceof shaka.media.SegmentReference) {
shaka.log.debug(
logPrefix,
'pop and abort prefetched segment at time:', reference.startTime);
} else {
shaka.log.debug(logPrefix, 'pop and abort prefetched init segment');
}
}
}
/**
* The prefix of the logs that are created in this class.
* @return {string}
* @private
*/
static logPrefix_(stream) {
return 'SegmentPrefetch(' + stream.type + ':' + stream.id + ')';
}
};
/**
* @summary
* This class manages a segment prefetch operation.
*/
shaka.media.SegmentPrefetchOperation = class {
/**
* @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
*/
constructor(fetchDispatcher) {
/** @private {shaka.media.SegmentPrefetch.FetchDispatcher} */
this.fetchDispatcher_ = fetchDispatcher;
/** @private {?function(BufferSource):!Promise} */
this.streamDataCallback_ = null;
/** @private {?shaka.net.NetworkingEngine.PendingRequest} */
this.operation_ = null;
}
/**
* @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
*/
replaceFetchDispatcher(fetchDispatcher) {
this.fetchDispatcher_ = fetchDispatcher;
}
/**
* Fetch a segments
*
* @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
* reference
* @param {!shaka.extern.Stream} stream
* @public
*/
dispatchFetch(reference, stream) {
// We need to store the data, because streamDataCallback_ might not be
// available when you start getting the first data.
let buffered = new Uint8Array(0);
this.operation_ = this.fetchDispatcher_(
reference, stream, async (data) => {
if (buffered.byteLength > 0) {
buffered = shaka.util.Uint8ArrayUtils.concat(buffered, data);
} else {
buffered = data;
}
if (this.streamDataCallback_) {
await this.streamDataCallback_(buffered);
buffered = new Uint8Array(0);
}
});
}
/**
* Get the operation of prefetched segment if already exists.
*
* @return {?shaka.net.NetworkingEngine.PendingRequest} op
* @public
*/
getOperation() {
return this.operation_;
}
/**
* @param {?function(BufferSource):!Promise} streamDataCallback
* @public
*/
setStreamDataCallback(streamDataCallback) {
this.streamDataCallback_ = streamDataCallback;
}
/**
* Abort the current operation if exists.
*/
abort() {
if (this.operation_) {
this.operation_.abort();
}
}
};
/**
* @typedef {function(
* !(shaka.media.InitSegmentReference|shaka.media.SegmentReference),
* shaka.extern.Stream,
* ?function(BufferSource):!Promise=
* ):!shaka.net.NetworkingEngine.PendingRequest}
*
* @description
* A callback function that fetches a segment.
* @export
*/
shaka.media.SegmentPrefetch.FetchDispatcher;