rx.backpressure.js

// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

;(function (factory) {
    var objectTypes = {
        'boolean': false,
        'function': true,
        'object': true,
        'number': false,
        'string': false,
        'undefined': false
    };

    var root = (objectTypes[typeof window] && window) || this,
        freeExports = objectTypes[typeof exports] && exports && !exports.nodeType && exports,
        freeModule = objectTypes[typeof module] && module && !module.nodeType && module,
        moduleExports = freeModule && freeModule.exports === freeExports && freeExports,
        freeGlobal = objectTypes[typeof global] && global;
    
    if (freeGlobal && (freeGlobal.global === freeGlobal || freeGlobal.window === freeGlobal)) {
        root = freeGlobal;
    }

    // Because of build optimizers
    if (typeof define === 'function' && define.amd) {
        define(['rx', 'exports'], function (Rx, exports) {
            root.Rx = factory(root, exports, Rx);
            return root.Rx;
        });
    } else if (typeof module === 'object' && module && module.exports === freeExports) {
        module.exports = factory(root, module.exports, require('./rx'));
    } else {
        root.Rx = factory(root, {}, root.Rx);
    }
}.call(this, function (root, exp, Rx, undefined) {
    
  // References
  var Observable = Rx.Observable,
    observableProto = Observable.prototype,
    AnonymousObservable = Rx.AnonymousObservable,
    CompositeDisposable = Rx.CompositeDisposable,
    Subject = Rx.Subject,
    Observer = Rx.Observer,
    disposableEmpty = Rx.Disposable.empty,
    disposableCreate = Rx.Disposable.create,
    inherits = Rx.internals.inherits,
    addProperties = Rx.internals.addProperties,  
    timeoutScheduler = Rx.Scheduler.timeout,
    identity = Rx.helpers.identity;

  var objectDisposed = 'Object has been disposed';
  function checkDisposed() { if (this.isDisposed) { throw new Error(objectDisposed); } }

  var PausableObservable = (function (_super) {

    inherits(PausableObservable, _super);

    function subscribe(observer) {
      var conn = this.source.publish(),
        subscription = conn.subscribe(observer),
        connection = disposableEmpty;

      var pausable = this.subject.distinctUntilChanged().subscribe(function (b) {
        if (b) {
          connection = conn.connect();
        } else {
          connection.dispose();
          connection = disposableEmpty;
        }
      });

      return new CompositeDisposable(subscription, connection, pausable);
    }

    function PausableObservable(source, subject) {
      this.source = source;
      this.subject = subject || new Subject();
      this.isPaused = true;
      _super.call(this, subscribe);
    }

    PausableObservable.prototype.pause = function () {
      if (this.isPaused === true){
        return;
      }
      this.isPaused = true;
      this.subject.onNext(false);
    };

    PausableObservable.prototype.resume = function () {
      if (this.isPaused === false){
        return;
      }
      this.isPaused = false;
      this.subject.onNext(true);
    };

    return PausableObservable;

  }(Observable));

  /**
   * Pauses the underlying observable sequence based upon the observable sequence which yields true/false.
   * @example
   * var pauser = new Rx.Subject();
   * var source = Rx.Observable.interval(100).pausable(pauser);
   * @param {Observable} pauser The observable sequence used to pause the underlying sequence.
   * @returns {Observable} The observable sequence which is paused based upon the pauser.
   */
  observableProto.pausable = function (pauser) {
    return new PausableObservable(this, pauser);
  };
  function combineLatestSource(source, subject, resultSelector) {
    return new AnonymousObservable(function (observer) {
      var n = 2,
        hasValue = [false, false],
        hasValueAll = false,
        isDone = false,
        values = new Array(n);

      function next(x, i) {
        values[i] = x
        var res;
        hasValue[i] = true;
        if (hasValueAll || (hasValueAll = hasValue.every(identity))) {
          try {
            res = resultSelector.apply(null, values);
          } catch (ex) {
            observer.onError(ex);
            return;
          }
          observer.onNext(res);
        } else if (isDone) {
          observer.onCompleted();
        }
      }

      return new CompositeDisposable(
        source.subscribe(
          function (x) {
            next(x, 0);
          },
          observer.onError.bind(observer),
          function () {
            isDone = true;
            observer.onCompleted();
          }),
        subject.subscribe(
          function (x) {
            next(x, 1);
          },
          observer.onError.bind(observer))
        );
    });
  }

  var PausableBufferedObservable = (function (_super) {

    inherits(PausableBufferedObservable, _super);

    function subscribe(observer) {
      var q = [], previous = true;
      
      var subscription =  
        combineLatestSource(
          this.source,
          this.subject.distinctUntilChanged(), 
          function (data, shouldFire) {
            return { data: data, shouldFire: shouldFire };      
          })
          .subscribe(
            function (results) {
              if (results.shouldFire && previous) {
                observer.onNext(results.data);
              }
              if (results.shouldFire && !previous) {
                while (q.length > 0) {
                  observer.onNext(q.shift());
                }
                previous = true;
              } else if (!results.shouldFire && !previous) {
                q.push(results.data);
              } else if (!results.shouldFire && previous) {
                previous = false;
              }

            }, 
            function (err) {
              // Empty buffer before sending error
              while (q.length > 0) {
                observer.onNext(q.shift());
              }
              observer.onError(err);
            },
            function () {
              // Empty buffer before sending completion
              while (q.length > 0) {
                observer.onNext(q.shift());
              }
              observer.onCompleted();              
            }
          );

      this.subject.onNext(false);

      return subscription;      
    }

    function PausableBufferedObservable(source, subject) {
      this.source = source;
      this.subject = subject || new Subject();
      this.isPaused = true;
      _super.call(this, subscribe);
    }

    PausableBufferedObservable.prototype.pause = function () {
      if (this.isPaused === true){
        return;
      }
      this.isPaused = true;
      this.subject.onNext(false);
    };

    PausableBufferedObservable.prototype.resume = function () {
      if (this.isPaused === false){
        return;
      }
      this.isPaused = false;
      this.subject.onNext(true);
    };

    return PausableBufferedObservable; 

  }(Observable));

  /**
   * Pauses the underlying observable sequence based upon the observable sequence which yields true/false,
   * and yields the values that were buffered while paused.
   * @example
   * var pauser = new Rx.Subject();
   * var source = Rx.Observable.interval(100).pausableBuffered(pauser);
   * @param {Observable} pauser The observable sequence used to pause the underlying sequence.
   * @returns {Observable} The observable sequence which is paused based upon the pauser.
   */  
  observableProto.pausableBuffered = function (subject) {
    return new PausableBufferedObservable(this, subject);
  };

  /**
   * Attaches a controller to the observable sequence with the ability to queue.
   * @example
   * var source = Rx.Observable.interval(100).controlled();
   * source.request(3); // Reads 3 values
   * @param {Observable} pauser The observable sequence used to pause the underlying sequence.
   * @returns {Observable} The observable sequence which is paused based upon the pauser.
   */ 
  observableProto.controlled = function (enableQueue) {
    if (enableQueue == null) {  enableQueue = true; }
    return new ControlledObservable(this, enableQueue);
  };
  var ControlledObservable = (function (_super) {

    inherits(ControlledObservable, _super);

    function subscribe (observer) {
      return this.source.subscribe(observer);
    }

    function ControlledObservable (source, enableQueue) {
      _super.call(this, subscribe);
      this.subject = new ControlledSubject(enableQueue);
      this.source = source.multicast(this.subject).refCount();
    }

    ControlledObservable.prototype.request = function (numberOfItems) {
      if (numberOfItems == null) { numberOfItems = -1; }
      return this.subject.request(numberOfItems);
    };

    return ControlledObservable;

  }(Observable));

    var ControlledSubject = Rx.ControlledSubject = (function (_super) {

        function subscribe (observer) {
            return this.subject.subscribe(observer);
        }

        inherits(ControlledSubject, _super);

        function ControlledSubject(enableQueue) {
            if (enableQueue == null) {
                enableQueue = true;
            }

            _super.call(this, subscribe);
            this.subject = new Subject();
            this.enableQueue = enableQueue;
            this.queue = enableQueue ? [] : null;
            this.requestedCount = 0;
            this.requestedDisposable = disposableEmpty;
            this.error = null;
            this.hasFailed = false;
            this.hasCompleted = false;
            this.controlledDisposable = disposableEmpty;
        }

        addProperties(ControlledSubject.prototype, Observer, {
            onCompleted: function () {
                checkDisposed.call(this);
                this.hasCompleted = true;

                if (!this.enableQueue || this.queue.length === 0) {
                    this.subject.onCompleted();
                }
            },
            onError: function (error) {
                checkDisposed.call(this);
                this.hasFailed = true;
                this.error = error;

                if (!this.enableQueue || this.queue.length === 0) {
                    this.subject.onError(error);
                }   
            },
            onNext: function (value) {
                checkDisposed.call(this);
                var hasRequested = false;

                if (this.requestedCount === 0) {
                    if (this.enableQueue) {
                        this.queue.push(value);
                    }
                } else {
                    if (this.requestedCount !== -1) {
                        if (this.requestedCount-- === 0) {
                            this.disposeCurrentRequest();
                        }
                    }
                    hasRequested = true;
                }

                if (hasRequested) {
                    this.subject.onNext(value);
                }
            },
            _processRequest: function (numberOfItems) {
                if (this.enableQueue) {
                    //console.log('queue length', this.queue.length);

                    while (this.queue.length >= numberOfItems && numberOfItems > 0) {
                        //console.log('number of items', numberOfItems);
                        this.subject.onNext(this.queue.shift());
                        numberOfItems--;
                    }

                    if (this.queue.length !== 0) {
                        return { numberOfItems: numberOfItems, returnValue: true };
                    } else {
                        return { numberOfItems: numberOfItems, returnValue: false };
                    }
                }

                if (this.hasFailed) {
                    this.subject.onError(this.error);
                    this.controlledDisposable.dispose();
                    this.controlledDisposable = disposableEmpty;
                } else if (this.hasCompleted) {
                    this.subject.onCompleted();
                    this.controlledDisposable.dispose();
                    this.controlledDisposable = disposableEmpty;                   
                }

                return { numberOfItems: numberOfItems, returnValue: false };
            },
            request: function (number) {
                checkDisposed.call(this);
                this.disposeCurrentRequest();
                var self = this,
                    r = this._processRequest(number);

                number = r.numberOfItems;
                if (!r.returnValue) {
                    this.requestedCount = number;
                    this.requestedDisposable = disposableCreate(function () {
                        self.requestedCount = 0;
                    });

                    return this.requestedDisposable
                } else {
                    return disposableEmpty;
                }
            },
            disposeCurrentRequest: function () {
                this.requestedDisposable.dispose();
                this.requestedDisposable = disposableEmpty;
            },

            dispose: function () {
                this.isDisposed = true;
                this.error = null;
                this.subject.dispose();
                this.requestedDisposable.dispose();
            }
        });

        return ControlledSubject;
    }(Observable));
    return Rx;
}));