shaka-player
Version:
DASH/EME video player library
262 lines (238 loc) • 8.74 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.util.AbortableOperation');
goog.require('shaka.util.Error');
goog.require('shaka.util.PublicPromise');
/**
* A utility to wrap abortable operations. Note that these are not cancelable.
* Cancellation implies undoing what has been done so far, whereas aborting only
* means that further work is stopped.
*
* @implements {shaka.extern.IAbortableOperation<T>}
* @template T
* @export
*/
shaka.util.AbortableOperation = class {
/**
* @param {!Promise<T>} promise
* A Promise which represents the underlying operation. It is resolved when
* the operation is complete, and rejected if the operation fails or is
* aborted. Aborted operations should be rejected with a shaka.util.Error
* object using the error code OPERATION_ABORTED.
* @param {function():!Promise} onAbort
* Will be called by this object to abort the underlying operation.
* This is not cancellation, and will not necessarily result in any work
* being undone. abort() should return a Promise which is resolved when the
* underlying operation has been aborted. The returned Promise should never
* be rejected.
*/
constructor(promise, onAbort) {
/** @const {!Promise<T>} */
this.promise = promise;
/** @private {function():!Promise} */
this.onAbort_ = onAbort;
/** @private {?Promise} */
this.abortPromise_ = null;
}
/**
* @return {boolean} True if the operation has been aborted.
* @export
*/
get aborted() {
return this.abortPromise_ !== null;
}
/**
* @param {!shaka.util.Error} error
* @return {!shaka.util.AbortableOperation} An operation which has already
* failed with the error given by the caller.
* @export
*/
static failed(error) {
return new shaka.util.AbortableOperation(
Promise.reject(error),
() => Promise.resolve());
}
/**
* @return {!shaka.util.AbortableOperation} An operation which has already
* failed with the error OPERATION_ABORTED.
* @export
*/
static aborted() {
const p = Promise.reject(shaka.util.AbortableOperation.abortError());
// Silence uncaught rejection errors, which may otherwise occur any place
// we don't explicitly handle aborted operations.
p.catch(() => {});
return new shaka.util.AbortableOperation(p, () => Promise.resolve());
}
/** @return {!shaka.util.Error} */
static abortError() {
return new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.PLAYER,
shaka.util.Error.Code.OPERATION_ABORTED);
}
/**
* @param {U} value
* @return {!shaka.util.AbortableOperation.<U>} An operation which has already
* completed with the given value.
* @template U
* @export
*/
static completed(value) {
return new shaka.util.AbortableOperation(
Promise.resolve(value),
() => Promise.resolve());
}
/**
* @param {!Promise<U>} promise
* @return {!shaka.util.AbortableOperation.<U>} An operation which cannot be
* aborted. It will be completed when the given Promise is resolved, or
* will be failed when the given Promise is rejected.
* @template U
* @export
*/
static notAbortable(promise) {
return new shaka.util.AbortableOperation(
promise,
// abort() here will return a Promise which is resolved when the input
// promise either resolves or fails.
() => promise.catch(() => {}));
}
/**
* @override
* @export
*/
abort() {
if (!this.abortPromise_) {
this.abortPromise_ = this.onAbort_();
}
return this.abortPromise_;
}
/**
* @param {!Array<!shaka.util.AbortableOperation>} operations
* @return {!shaka.util.AbortableOperation} An operation which is resolved
* when all operations are successful and fails when any operation fails.
* For this operation, abort() aborts all given operations.
* @export
*/
static all(operations) {
return new shaka.util.AbortableOperation(
Promise.all(operations.map((op) => op.promise)),
() => Promise.all(operations.map((op) => op.abort())));
}
/**
* @override
* @export
*/
finally(onFinal) {
this.promise.then((value) => onFinal(true), (e) => onFinal(false));
return this;
}
/**
* @param {(undefined|
* function(T):U|
* function(T):!Promise<U>|
* function(T):!shaka.util.AbortableOperation.<U>)} onSuccess
* A callback to be invoked after this operation is complete, to chain to
* another operation. The callback can return a plain value, a Promise to
* an asynchronous value, or another AbortableOperation.
* @param {function(*)=} onError
* An optional callback to be invoked if this operation fails, to perform
* some cleanup or error handling. Analogous to the second parameter of
* Promise.prototype.then.
* @return {!shaka.util.AbortableOperation.<U>} An operation which is resolved
* when this operation and the operation started by the callback are both
* complete.
* @template U
* @export
*/
chain(onSuccess, onError) {
const newPromise = new shaka.util.PublicPromise();
// Silence uncaught rejection errors, which may otherwise occur any place
// we don't explicitly handle aborted operations.
newPromise.catch(() => {});
const abortError = shaka.util.AbortableOperation.abortError();
// If called before "this" completes, just abort "this".
let abort = () => {
newPromise.reject(abortError);
return this.abort();
};
const makeCallback = (isSuccess) => {
return (value) => {
if (this.abortPromise_ && isSuccess) {
// If "this" is not abortable(), or if abort() is called after "this"
// is complete but before the next stage in the chain begins, we
// should stop right away.
newPromise.reject(abortError);
return;
}
const cb = isSuccess ? onSuccess : onError;
if (!cb) {
// No callback? Pass it along.
const next = isSuccess ? newPromise.resolve : newPromise.reject;
next(value);
return;
}
// Call the callback, interpret the return value, set the Promise state,
// and get the next abort function.
abort = shaka.util.AbortableOperation.wrapChainCallback_(
cb, value, newPromise);
};
};
this.promise.then(makeCallback(true), makeCallback(false));
return new shaka.util.AbortableOperation(
newPromise,
// By creating a closure around abort(), we can update the value of
// abort() at various stages.
() => abort());
}
/**
* @param {(function(T):U|
* function(T):!Promise<U>|
* function(T):!shaka.util.AbortableOperation.<U>|
* function(*))} callback
* A callback to be invoked with the given value.
* @param {T} value
* @param {!shaka.util.PublicPromise} newPromise The promise for the next
* stage in the chain.
* @return {function():!Promise} The next abort() function for the chain.
* @private
* @template T, U
*/
static wrapChainCallback_(callback, value, newPromise) {
try {
const ret = callback(value);
if (ret && ret.promise && ret.abort) {
// This is an abortable operation, with its own abort() method.
// After this point, abort() should abort the operation from the
// callback, and the new promise should be tied to the promise
// from the callback's operation.
newPromise.resolve(ret.promise);
// This used to say "return ret.abort;", but it caused subtle issues by
// unbinding part of the abort chain. There is now a test to ensure
// that we don't call abort with the wrong "this".
return () => ret.abort();
} else {
// This is a Promise or a plain value, and this step cannot be aborted.
newPromise.resolve(ret);
// Abort is complete when the returned value/Promise is resolved or
// fails, but never fails itself nor returns a value.
return () => Promise.resolve(ret).then(() => {}, () => {});
}
} catch (exception) {
// The callback threw an exception or error. Reject the new Promise and
// resolve any future abort call right away.
newPromise.reject(exception);
return () => Promise.resolve();
}
}
};
/**
* @const {!Promise<T>}
* @exportInterface
*/
// eslint-disable-next-line no-restricted-syntax
shaka.util.AbortableOperation.prototype.promise;