es6/operator/bufferCount.js

import { Subscriber } from '../Subscriber';
/**
 * 缓冲源 Observable 的值直到缓冲数量到达设定的 `bufferSize`.
 *
 * <span class="informal">将过往的值收集到一个数组中，当数组数量到达设定的 bufferSize 时发出该数组。</span>
 *
 * <img src="./img/bufferCount.png" width="100%">
 *
 * 缓冲源 Observable 的N个值(N = bufferSize)，然后发出该缓冲区并进行清理，再然后开启一个新的缓存区，新缓存区会新缓存M个值(M = startBufferEvery)。
 * 如果`startBufferEvery`没有提供或者为`null`, 新的缓冲会在源开始的时候开启并且在每次发出的时候关闭。
 *
 * @example <caption>将最后两次点击事件作为数组发出</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var buffered = clicks.bufferCount(2);
 * buffered.subscribe(x => console.log(x));
 *
 * @example <caption>在每次点击的时候, 以数组的形式发出最后两次点击</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var buffered = clicks.bufferCount(2, 1);
 * buffered.subscribe(x => console.log(x));
 *
 * @see {@link buffer}
 * @see {@link bufferTime}
 * @see {@link bufferToggle}
 * @see {@link bufferWhen}
 * @see {@link pairwise}
 * @see {@link windowCount}
 *
 * @param {number} bufferSize 缓存区的最大长度。
 * @param {number} [startBufferEvery] 确定何时启用新的缓冲区。
 * 例如上面图中所示，如果`startBufferEvery`是`2`, 那么隔一个数据会开一个新
 * 的缓冲区。 默认情况下，将在源的起始处启用新的缓冲区。
 * @return {Observable<T[]>} 缓存值数组的 Observable 。
 * @method bufferCount
 * @owner Observable
 */
export function bufferCount(bufferSize, startBufferEvery = null) {
    return this.lift(new BufferCountOperator(bufferSize, startBufferEvery));
}
class BufferCountOperator {
    constructor(bufferSize, startBufferEvery) {
        this.bufferSize = bufferSize;
        this.startBufferEvery = startBufferEvery;
        if (!startBufferEvery || bufferSize === startBufferEvery) {
            this.subscriberClass = BufferCountSubscriber;
        }
        else {
            this.subscriberClass = BufferSkipCountSubscriber;
        }
    }
    call(subscriber, source) {
        return source.subscribe(new this.subscriberClass(subscriber, this.bufferSize, this.startBufferEvery));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class BufferCountSubscriber extends Subscriber {
    constructor(destination, bufferSize) {
        super(destination);
        this.bufferSize = bufferSize;
        this.buffer = [];
    }
    _next(value) {
        const buffer = this.buffer;
        buffer.push(value);
        if (buffer.length == this.bufferSize) {
            this.destination.next(buffer);
            this.buffer = [];
        }
    }
    _complete() {
        const buffer = this.buffer;
        if (buffer.length > 0) {
            this.destination.next(buffer);
        }
        super._complete();
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class BufferSkipCountSubscriber extends Subscriber {
    constructor(destination, bufferSize, startBufferEvery) {
        super(destination);
        this.bufferSize = bufferSize;
        this.startBufferEvery = startBufferEvery;
        this.buffers = [];
        this.count = 0;
    }
    _next(value) {
        const { bufferSize, startBufferEvery, buffers, count } = this;
        this.count++;
        if (count % startBufferEvery === 0) {
            buffers.push([]);
        }
        for (let i = buffers.length; i--;) {
            const buffer = buffers[i];
            buffer.push(value);
            if (buffer.length === bufferSize) {
                buffers.splice(i, 1);
                this.destination.next(buffer);
            }
        }
    }
    _complete() {
        const { buffers, destination } = this;
        while (buffers.length > 0) {
            let buffer = buffers.shift();
            if (buffer.length > 0) {
                destination.next(buffer);
            }
        }
        super._complete();
    }
}
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