feat: Get an oscillator wave as an array

Author: tambien

Tone/source/oscillator/AMOscillator.ts

@@ -8,7 +8,8 @@ import { Signal } from "../../signal/Signal";
 import { Source } from "../Source";
 import { Oscillator } from "./Oscillator";
 import { AMConstructorOptions, AMOscillatorOptions,
-	NonCustomOscillatorType, ToneOscillatorInterface,
+	generateWaveform, NonCustomOscillatorType,
+	ToneOscillatorInterface, 
 	ToneOscillatorType } from "./OscillatorInterface";
 
 export { AMOscillatorOptions } from "./OscillatorInterface";
@@ -230,6 +231,10 @@ export class AMOscillator extends Source<AMOscillatorOptions> implements ToneOsc
 		this._carrier.partials = partials;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	/**
 	 * Clean up.
 	 */

Tone/source/oscillator/FMOscillator.ts

@@ -7,7 +7,7 @@ import { Signal } from "../../signal/Signal";
 import { Source } from "../Source";
 import { Oscillator } from "./Oscillator";
 import { FMConstructorOptions, FMOscillatorOptions,
-	NonCustomOscillatorType, ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
+	generateWaveform, NonCustomOscillatorType, ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
 
 export { FMOscillatorOptions } from "./OscillatorInterface";
 /**
@@ -245,6 +245,10 @@ export class FMOscillator extends Source<FMOscillatorOptions> implements ToneOsc
 		this._carrier.partials = partials;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	/**
 	 * Clean up.
 	 */

Tone/source/oscillator/FatOscillator.ts

@@ -7,7 +7,7 @@ import { Signal } from "../../signal/Signal";
 import { Source } from "../Source";
 import { Oscillator } from "./Oscillator";
 import { FatConstructorOptions, FatOscillatorOptions,
-	ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
+	generateWaveform, ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
 
 export { FatOscillatorOptions } from "./OscillatorInterface";
 
@@ -273,6 +273,10 @@ export class FatOscillator extends Source<FatOscillatorOptions> implements ToneO
 		this._type = this._oscillators[0].type;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	/**
 	 * Clean up.
 	 */

Tone/source/oscillator/OmniOscillator.ts

@@ -8,9 +8,9 @@ import { AMOscillator } from "./AMOscillator";
 import { FatOscillator } from "./FatOscillator";
 import { FMOscillator } from "./FMOscillator";
 import { Oscillator } from "./Oscillator";
-import { OmniOscillatorConstructorOptions,
-	OmniOscillatorOptions, OmniOscillatorType,
-	ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
+import { generateWaveform,
+	OmniOscillatorConstructorOptions, OmniOscillatorOptions,
+	OmniOscillatorType, ToneOscillatorInterface, ToneOscillatorType } from "./OscillatorInterface";
 import { PulseOscillator } from "./PulseOscillator";
 import { PWMOscillator } from "./PWMOscillator";
 
@@ -474,6 +474,10 @@ export class OmniOscillator<OscType extends AnyOscillator>
 		}
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	dispose(): this {
 		super.dispose();
 		this.detune.dispose();

Tone/source/oscillator/Oscillator.ts

@@ -4,10 +4,12 @@ import { noOp, readOnly } from "../../core/util/Interface";
 import { isDefined } from "../../core/util/TypeCheck";
 import { Signal } from "../../signal/Signal";
 import { Source } from "../Source";
-import { ToneOscillatorConstructorOptions, ToneOscillatorInterface,
+import { 
+	generateWaveform,
+	ToneOscillatorConstructorOptions, ToneOscillatorInterface,
 	ToneOscillatorOptions, ToneOscillatorType } from "./OscillatorInterface";
 import { ToneOscillatorNode } from "./ToneOscillatorNode";
-
+import { OfflineContext } from "../../core/context/OfflineContext";
 export { ToneOscillatorOptions, ToneOscillatorType } from "./OscillatorInterface";
 /**
  * Oscillator supports a number of features including
@@ -481,6 +483,10 @@ export class Oscillator extends Source<ToneOscillatorOptions> implements ToneOsc
 		this.type = this._type;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	dispose(): this {
 		super.dispose();
 		if (this._oscillator !== null) {

Tone/source/oscillator/OscillatorInterface.ts

@@ -2,6 +2,7 @@ import { AudioRange, Cents, Degrees, Frequency, Positive } from "../../core/type
 import { Omit } from "../../core/util/Interface";
 import { Signal } from "../../signal/Signal";
 import { SourceOptions } from "../Source";
+import { OfflineContext } from "../../core/context/OfflineContext";
 
 /**
  * The common interface of all Oscillators
@@ -14,6 +15,29 @@ export interface ToneOscillatorInterface {
 	phase: Degrees;
 	partials: number[];
 	partialCount?: number;
+	/**
+	 * Returns an array of values which represents the waveform.
+	 * @param length The length of the waveform to return
+	 */
+	asArray(length: number): Promise<Float32Array>;
+}
+
+/**
+ * Render a segment of the oscillator to an offline context and return the results as an array
+ */
+export async function generateWaveform(instance: any, length: number): Promise<Float32Array> {
+	const duration = length / instance.context.sampleRate;
+	const context = new OfflineContext(1, duration, instance.context.sampleRate);
+	const clone = new instance.constructor(Object.assign(instance.get(), { 
+		// should do 2 iterations
+		frequency: 2 / duration,
+		// zero out the detune
+		detune: 0,
+		context
+	})).toDestination();
+	clone.start(0);
+	const buffer = await context.render();
+	return buffer.getChannelData(0);
 }
 
 /**

Tone/source/oscillator/PWMOscillator.ts

@@ -5,7 +5,7 @@ import { Multiply } from "../../signal/Multiply";
 import { Signal } from "../../signal/Signal";
 import { Source } from "../Source";
 import { Oscillator } from "./Oscillator";
-import { PWMOscillatorOptions, ToneOscillatorInterface } from "./OscillatorInterface";
+import { generateWaveform, PWMOscillatorOptions, ToneOscillatorInterface } from "./OscillatorInterface";
 import { PulseOscillator } from "./PulseOscillator";
 
 export { PWMOscillatorOptions } from "./OscillatorInterface";
@@ -169,6 +169,10 @@ export class PWMOscillator extends Source<PWMOscillatorOptions> implements ToneO
 		this._modulator.phase = phase;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	/**
 	 * Clean up.
 	 */

Tone/source/oscillator/PulseOscillator.ts

@@ -6,7 +6,7 @@ import { Signal } from "../../signal/Signal";
 import { WaveShaper } from "../../signal/WaveShaper";
 import { Source } from "../Source";
 import { Oscillator } from "./Oscillator";
-import { PulseOscillatorOptions, ToneOscillatorInterface } from "./OscillatorInterface";
+import { generateWaveform, PulseOscillatorOptions, ToneOscillatorInterface } from "./OscillatorInterface";
 
 export { PulseOscillatorOptions } from "./OscillatorInterface";
 
@@ -197,6 +197,10 @@ export class PulseOscillator extends Source<PulseOscillatorOptions> implements T
 		return 0;
 	}
 
+	async asArray(length: number = 1024): Promise<Float32Array> {
+		return generateWaveform(this, length);
+	}
+
 	/**
 	 * Clean up method.
 	 */

test/helper/OscillatorTests.ts

@@ -60,5 +60,19 @@ export function OscillatorTests(Constr, args?): void {
 				expect(buffer.max()).to.be.at.most(1);
 			});
 		});
+
+		it("can generate a waveform", async () => {
+			const osc = new Constr();
+			const waveform = await osc.asArray();
+			waveform.forEach((v: number) => expect(v).to.be.within(-1, 1));
+			osc.dispose();
+		});
+
+		it("can generate a waveform of a specific length", async () => {
+			const osc = new Constr();
+			const waveform = await osc.asArray(256);
+			expect(waveform.length).to.equal(256);
+			osc.dispose();
+		});
 	});
 }