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//================================================================ /** * @packageDocumentation * @module std   *///================================================================import { ConditionVariable } from "./ConditionVariable";
/** * Latch for critical sections. *  * The `Latch` class blocks critical sections until the downward counter to be zero. Howver,  * unlike {@link Barrier} who can reusable that downward counter be reset whenever reach to the * zero, downward of the `Latch` is not reusable but diposable. *  * @author Jeongho Nam - https://github.com/samchon */export class Latch{    private cv_: ConditionVariable;    private count_: number;
    /* ---------------------------------------------------------        CONSTRUCTORS    --------------------------------------------------------- */    /**     * Initializer Constructor.     *      * @param size Size of the downward counter.     */    public constructor(size: number)    {        this.cv_ = new ConditionVariable();        this.count_ = size;    }
    /* ---------------------------------------------------------        WAIT FUNCTIONS    --------------------------------------------------------- */    /**     * Waits until the counter to be zero.     *      * Blocks the function calling until internal counter to be reached to the zero.      *      * If the {@link Latch} already has been reached to the zero, it would be returned      * immediately.     */    public async wait(): Promise<void>    {        if (this._Try_wait() === false)            await this.cv_.wait();    }
    /**     * Test whether the counter has been reached to the zero.     *      * The {@link try_wait} function tests whether the internal counter has been reached to the      * zero.     *      * @return Whether reached to zero or not.     */    public async try_wait(): Promise<boolean>    {        return this._Try_wait();    }
    /**     * Tries to wait until the counter to be zero in timeout.     *      * Attempts to block the function calling until internal counter to be reached to the zero     * in timeout. If succeeded to waiting the counter to be reached to the zero, it returns      * `true`. Otherwise, the {@link Latch} fails to reach to the zero in the given time, the      * function gives up the waiting and returns `false`.     *      * If the {@link Latch} already has been reached to the zero, it would return `true` directly.     *      * @param ms The maximum miliseconds for waiting.     * @return Whether succeeded to waiting in the given time.     */    public async wait_for(ms: number): Promise<boolean>    {        if (this._Try_wait() === true)            return true;        else            return await this.cv_.wait_for(ms);    }
    /**     * Tries to wait until the counter to be zero in time expiration.     *      * Attempts to block the function calling until internal counter to be reached to the zero     * in time expiration. If succeeded to waiting the counter to be reached to the zero, it      * returns `true`. Otherwise, the {@link Latch} fails to reach to the zero in the given time,      * the function gives up the waiting and returns `false`.     *      * If the {@link Latch} already has been reached to the zero, it would return `true` directly.     *      * @param at The maximum time point to wait.     * @return Whether succeeded to waiting in the given time.     */    public async wait_until(at: Date): Promise<boolean>    {        if (this._Try_wait() === true)            return true;        else            return await this.cv_.wait_until(at);    }
    private _Try_wait(): boolean    {        return this.count_ <= 0;    }
    /* -----------------------------------------------------------        ARRIVAL FUNCTIONS    ----------------------------------------------------------- */    /**     * Derecements the counter.     *      * Decrements the counter by *n* without blocking.      *      * If the parametric value *n* is equal to or greater than internal counter, so that the      * internal counter be equal to or less than zero, everyone who are {@link wait waiting} for     * the {@link Latch} would continue their execution.     *      * @param n Value of the decrement. Default is 1.     */    public async count_down(n: number = 1): Promise<void>    {        this.count_ -= n;        if (this._Try_wait() === true)            await this.cv_.notify_all();    }
    /**     * Decrements the counter and waits until the counter to be zero.     *      * Decrements the counter by *n* and blocks the section until internal counter to be zero.      *      * If the parametric value *n* is equal to or greater than internal counter, so that the      * internal counter be equal to or less than zero, everyone who are {@link wait waiting} for     * the {@link Latch} would continue their execution including this one.     *      * @param n Value of the decrement. Default is 1.     */    public async arrive_and_wait(n: number = 1): Promise<void>    {        await this.count_down(n);        await this.wait();    }}