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import { OperatorFunction } from '../types';
import { operate } from '../util/lift';
import { createOperatorSubscriber } from './OperatorSubscriber';
import { arrRemove } from '../util/arrRemove';
/**
* Buffers the source Observable values until the size hits the maximum
* `bufferSize` given.
*
* <span class="informal">Collects values from the past as an array, and emits
* that array only when its size reaches `bufferSize`.</span>
*
* 
*
* Buffers a number of values from the source Observable by `bufferSize` then
* emits the buffer and clears it, and starts a new buffer each
* `startBufferEvery` values. If `startBufferEvery` is not provided or is
* `null`, then new buffers are started immediately at the start of the source
* and when each buffer closes and is emitted.
*
* ## Examples
*
* Emit the last two click events as an array
*
* ```ts
* import { fromEvent, bufferCount } from 'rxjs';
*
* const clicks = fromEvent(document, 'click');
* const buffered = clicks.pipe(bufferCount(2));
* buffered.subscribe(x => console.log(x));
* ```
*
* On every click, emit the last two click events as an array
*
* ```ts
* import { fromEvent, bufferCount } from 'rxjs';
*
* const clicks = fromEvent(document, 'click');
* const buffered = clicks.pipe(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 The maximum size of the buffer emitted.
* @param {number} [startBufferEvery] Interval at which to start a new buffer.
* For example if `startBufferEvery` is `2`, then a new buffer will be started
* on every other value from the source. A new buffer is started at the
* beginning of the source by default.
* @return A function that returns an Observable of arrays of buffered values.
*/
export function bufferCount<T>(bufferSize: number, startBufferEvery: number | null = null): OperatorFunction<T, T[]> {
// If no `startBufferEvery` value was supplied, then we're
// opening and closing on the bufferSize itself.
startBufferEvery = startBufferEvery ?? bufferSize;
return operate((source, subscriber) => {
let buffers: T[][] = [];
let count = 0;
source.subscribe(
createOperatorSubscriber(
subscriber,
(value) => {
let toEmit: T[][] | null = null;
// Check to see if we need to start a buffer.
// This will start one at the first value, and then
// a new one every N after that.
if (count++ % startBufferEvery! === 0) {
buffers.push([]);
}
// Push our value into our active buffers.
for (const buffer of buffers) {
buffer.push(value);
// Check to see if we're over the bufferSize
// if we are, record it so we can emit it later.
// If we emitted it now and removed it, it would
// mutate the `buffers` array while we're looping
// over it.
if (bufferSize <= buffer.length) {
toEmit = toEmit ?? [];
toEmit.push(buffer);
}
}
if (toEmit) {
// We have found some buffers that are over the
// `bufferSize`. Emit them, and remove them from our
// buffers list.
for (const buffer of toEmit) {
arrRemove(buffers, buffer);
subscriber.next(buffer);
}
}
},
() => {
// When the source completes, emit all of our
// active buffers.
for (const buffer of buffers) {
subscriber.next(buffer);
}
subscriber.complete();
},
// Pass all errors through to consumer.
undefined,
() => {
// Clean up our memory when we finalize
buffers = null!;
}
)
);
});
}