Create 2 and 4 key map objects, use in color and glyph caches

src/common/MultiKeyMap.ts

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) 2022 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+export class TwoKeyMap<TFirst extends string | number, TSecond extends string | number, TValue> {
+  private _data: { [bg: string | number]: { [fg: string | number]: TValue | undefined } | undefined } = {};
+
+  public set(first: TFirst, second: TSecond, value: TValue): void {
+    if (!this._data[first]) {
+      this._data[first] = {};
+    }
+    this._data[first as string | number]![second] = value;
+  }
+
+  public get(first: TFirst, second: TSecond): TValue | undefined {
+    return this._data[first as string | number] ? this._data[first as string | number]![second] : undefined;
+  }
+
+  public clear(): void {
+    this._data = {};
+  }
+}
+
+export class FourKeyMap<TFirst extends string | number, TSecond extends string | number, TThird extends string | number, TFourth extends string | number, TValue> {
+  private _data: TwoKeyMap<TFirst, TSecond, TwoKeyMap<TThird, TFourth, TValue>> = new TwoKeyMap();
+
+  public set(first: TFirst, second: TSecond, third: TThird, fourth: TFourth, value: TValue): void {
+    if (!this._data.get(first, second)) {
+      this._data.set(first, second, new TwoKeyMap());
+    }
+    this._data.get(first, second)!.set(third, fourth, value);
+  }
+
+  public get(first: TFirst, second: TSecond, third: TThird, fourth: TFourth): TValue | undefined {
+    return this._data.get(first, second)?.get(third, fourth);
+  }
+
+  public clear(): void {
+    this._data.clear();
+  }
+}