@itwin/core-frontend/lib/cjs/internal/render/webgl/Sync.js

iTwin.js frontend components

"use strict";
/*---------------------------------------------------------------------------------------------
* Copyright (c) Bentley Systems, Incorporated. All rights reserved.
* See LICENSE.md in the project root for license terms and full copyright notice.
*--------------------------------------------------------------------------------------------*/
/** @packageDocumentation
 * @module WebGL
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.isSynchronized = isSynchronized;
exports.sync = sync;
exports.desync = desync;
/** Returns true if the target and observer are already synchronized.
 * @internal
 */
function isSynchronized(target, observer) {
    const token = observer.syncToken;
    return undefined !== token && token.target === target && token.syncKey === target.syncKey;
}
/** If the observer is already synchronized with the target, returns true.
 * Otherwise, synchronizes the observer's [[SyncToken]] with the target and returns false.
 * This is used, for example, to associate uniform variable state with shader programs such that the program can trivially detect if the state has changed since the last time
 * the variable's value was set.
 * @internal
 */
function sync(target, observer) {
    const syncKey = target.syncKey;
    const token = observer.syncToken;
    if (undefined === token) {
        observer.syncToken = { target, syncKey };
        return false;
    }
    if (token.syncKey === syncKey && token.target === target)
        return true;
    token.syncKey = syncKey;
    token.target = target;
    return false;
}
/** Mark the [[SyncTarget]] as having changed in a way that affects associated [[SyncObserver]]s.
 * The next time [[sync]] is used, all [[SyncToken]] objects associated with the target will be recognized as out of sync.
 * @internal
 */
function desync(target) {
    // Let's make the relatively safe assumption that we will never roll over, and the even safer assumption that if we do, no outstanding SyncTokens holding a very small value will exist at that time.
    if (target.syncKey < Number.MAX_SAFE_INTEGER)
        ++target.syncKey;
    else
        target.syncKey = Number.MIN_SAFE_INTEGER;
}
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