igir/dist/src/async/elasticSemaphore.js

🕹 A zero-setup ROM collection manager that sorts, filters, extracts or archives, patches, and reports on collections of any size on any OS.

import { Semaphore } from 'async-mutex';
/**
 * Wrapper for an `async-mutex` {@link Semaphore} that can have its total increased if a weight
 * exceeds the maximum.
 */
export default class ElasticSemaphore {
    semaphoreValue;
    semaphore;
    _openLocks = 0;
    constructor(value) {
        this.semaphoreValue = Math.ceil(value);
        this.semaphore = new Semaphore(this.semaphoreValue);
    }
    /**
     * Run some {@link callback} with a required {@link weight}.
     */
    async runExclusive(callback, weight) {
        const weightNormalized = Math.max(1, Math.ceil(weight));
        // NOTE(cemmer): this semaphore can take a measurable amount of time to actually call the
        //  callback. This is particularly noticeable when using single threads (e.g. via Async.js).
        //  Try to only use semaphores to traffic cop multiple concurrent threads.
        const result = await this.semaphore.runExclusive(async (value) => {
            this._openLocks += 1;
            return await callback(value);
        }, 
        // If the weight of this call is larger than the max value then just use the max value
        Math.min(weightNormalized, this.semaphoreValue));
        this._openLocks -= 1;
        return result;
    }
    /**
     * Get the number of currently open/acquired locks.
     */
    openLocks() {
        return this._openLocks;
    }
}