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node_modules/rxjs/_esm2015/operators/takeLast.js

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+import { Subscriber } from '../Subscriber';
+import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
+import { EmptyObservable } from '../observable/EmptyObservable';
+/**
+ * Emits only the last `count` values emitted by the source Observable.
+ *
+ * <span class="informal">Remembers the latest `count` values, then emits those
+ * only when the source completes.</span>
+ *
+ * <img src="./img/takeLast.png" width="100%">
+ *
+ * `takeLast` returns an Observable that emits at most the last `count` values
+ * emitted by the source Observable. If the source emits fewer than `count`
+ * values then all of its values are emitted. This operator must wait until the
+ * `complete` notification emission from the source in order to emit the `next`
+ * values on the output Observable, because otherwise it is impossible to know
+ * whether or not more values will be emitted on the source. For this reason,
+ * all values are emitted synchronously, followed by the complete notification.
+ *
+ * @example <caption>Take the last 3 values of an Observable with many values</caption>
+ * var many = Rx.Observable.range(1, 100);
+ * var lastThree = many.takeLast(3);
+ * lastThree.subscribe(x => console.log(x));
+ *
+ * @see {@link take}
+ * @see {@link takeUntil}
+ * @see {@link takeWhile}
+ * @see {@link skip}
+ *
+ * @throws {ArgumentOutOfRangeError} When using `takeLast(i)`, it delivers an
+ * ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0`.
+ *
+ * @param {number} count The maximum number of values to emit from the end of
+ * the sequence of values emitted by the source Observable.
+ * @return {Observable<T>} An Observable that emits at most the last count
+ * values emitted by the source Observable.
+ * @method takeLast
+ * @owner Observable
+ */
+export function takeLast(count) {
+    return function takeLastOperatorFunction(source) {
+        if (count === 0) {
+            return new EmptyObservable();
+        }
+        else {
+            return source.lift(new TakeLastOperator(count));
+        }
+    };
+}
+class TakeLastOperator {
+    constructor(total) {
+        this.total = total;
+        if (this.total < 0) {
+            throw new ArgumentOutOfRangeError;
+        }
+    }
+    call(subscriber, source) {
+        return source.subscribe(new TakeLastSubscriber(subscriber, this.total));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class TakeLastSubscriber extends Subscriber {
+    constructor(destination, total) {
+        super(destination);
+        this.total = total;
+        this.ring = new Array();
+        this.count = 0;
+    }
+    _next(value) {
+        const ring = this.ring;
+        const total = this.total;
+        const count = this.count++;
+        if (ring.length < total) {
+            ring.push(value);
+        }
+        else {
+            const index = count % total;
+            ring[index] = value;
+        }
+    }
+    _complete() {
+        const destination = this.destination;
+        let count = this.count;
+        if (count > 0) {
+            const total = this.count >= this.total ? this.total : this.count;
+            const ring = this.ring;
+            for (let i = 0; i < total; i++) {
+                const idx = (count++) % total;
+                destination.next(ring[idx]);
+            }
+        }
+        destination.complete();
+    }
+}
+//# sourceMappingURL=takeLast.js.map