Initial Move from Azure DevOps to GitHub

src/Common/ObjectCache.ts

@@ -0,0 +1,56 @@
+import { HashMap } from "./HashMap";
+
+export class ObjectCache<T> extends HashMap<T> {
+  private keyQueue: string[]; // Last touched key FIFO to purge cache if too big.
+  private maxNbElements: number;
+
+  public constructor(maxNbElements: number) {
+    super();
+    this.keyQueue = [];
+    this.maxNbElements = maxNbElements;
+    this.clear();
+  }
+
+  public clear(): void {
+    super.clear();
+    this.keyQueue = [];
+  }
+
+  public get(key: string): T {
+    this.markKeyAsTouched(key);
+    return super.get(key);
+  }
+
+  public set(key: string, value: T): void {
+    super.set(key, value);
+
+    this.markKeyAsTouched(key);
+
+    if (super.size() > this.maxNbElements && key !== this.keyQueue[0]) {
+      this.reduceCacheSize();
+    }
+  }
+
+  /**
+   * Invalidate elements to keep the total number below the limit
+   */
+  private reduceCacheSize(): void {
+    // remove a key
+    const oldKey = this.keyQueue.shift();
+    if (oldKey) {
+      super.delete(oldKey);
+    }
+  }
+
+  /**
+   * Bubble up this key as new.
+   * @param key
+   */
+  private markKeyAsTouched(key: string) {
+    const n = this.keyQueue.indexOf(key);
+    if (n > -1) {
+      this.keyQueue.splice(n, 1);
+    }
+    this.keyQueue.push(key);
+  }
+}