Introduce CharacterClassifier

src/vs/editor/common/core/characterClassifier.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+'use strict';
+
+/**
+ * A fast character classifier that uses a compact array for ASCII values.
+ */
+export class CharacterClassifier<T> {
+	/**
+	 * Maintain a compact (fully initialized ASCII map for quickly classifying ASCII characters - used more often in code).
+	 */
+	private _asciiMap: T[];
+
+	/**
+	 * The entire map (sparse array).
+	 */
+	private _map: T[];
+
+	private _defaultValue: T;
+
+	constructor(defaultValue:T) {
+		this._defaultValue = defaultValue;
+		this._asciiMap = CharacterClassifier._createAsciiMap(defaultValue);
+		this._map = [];
+	}
+
+	private static _createAsciiMap<T>(defaultValue:T): T[] {
+		let asciiMap:T[] = [];
+		for (let i = 0; i < 256; i++) {
+			asciiMap[i] = defaultValue;
+		}
+		return asciiMap;
+	}
+
+	public set(charCode:number, value:T): void {
+		if (charCode >= 0 && charCode < 256) {
+			this._asciiMap[charCode] = value;
+		} else {
+			this._map[charCode] = value;
+		}
+	}
+
+	public get(charCode:number): T {
+		if (charCode >= 0 && charCode < 256) {
+			return this._asciiMap[charCode];
+		} else {
+			return this._map[charCode] || this._defaultValue;
+		}
+	}
+}

src/vs/editor/test/common/core/characterClassifier.test.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+'use strict';
+
+import * as assert from 'assert';
+import {CharacterClassifier} from 'vs/editor/common/core/characterClassifier';
+import {CharCode} from 'vs/base/common/charCode';
+
+suite('CharacterClassifier', () => {
+
+	test('works', () => {
+		let classifier = new CharacterClassifier(0);
+
+		assert.equal(classifier.get(-1), 0);
+		assert.equal(classifier.get(0), 0);
+		assert.equal(classifier.get(CharCode.a), 0);
+		assert.equal(classifier.get(CharCode.b), 0);
+		assert.equal(classifier.get(CharCode.z), 0);
+		assert.equal(classifier.get(255), 0);
+		assert.equal(classifier.get(1000), 0);
+		assert.equal(classifier.get(2000), 0);
+
+		classifier.set(CharCode.a, 1);
+		classifier.set(CharCode.z, 2);
+		classifier.set(1000, 3);
+
+		assert.equal(classifier.get(-1), 0);
+		assert.equal(classifier.get(0), 0);
+		assert.equal(classifier.get(CharCode.a), 1);
+		assert.equal(classifier.get(CharCode.b), 0);
+		assert.equal(classifier.get(CharCode.z), 2);
+		assert.equal(classifier.get(255), 0);
+		assert.equal(classifier.get(1000), 3);
+		assert.equal(classifier.get(2000), 0);
+	});
+
+});
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