mediabunny/src/wave/riff-reader.ts

Pure TypeScript media toolkit for reading, writing, and converting media files, directly in the browser.

/*!
 * Copyright (c) 2025-present, Vanilagy and contributors
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

import { Reader } from '../reader';

export class RiffReader {
	pos = 0;
	littleEndian = true;

	constructor(public reader: Reader) {}

	readBytes(length: number) {
		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + length);
		this.pos += length;

		return new Uint8Array(view.buffer, offset, length);
	}

	readU16() {
		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 2);
		this.pos += 2;

		return view.getUint16(offset, this.littleEndian);
	}

	readU32() {
		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 4);
		this.pos += 4;

		return view.getUint32(offset, this.littleEndian);
	}

	readU64() {
		let low: number;
		let high: number;

		if (this.littleEndian) {
			low = this.readU32();
			high = this.readU32();
		} else {
			high = this.readU32();
			low = this.readU32();
		}

		return high * 0x100000000 + low;
	}

	readAscii(length: number) {
		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + length);
		this.pos += length;

		let str = '';
		for (let i = 0; i < length; i++) {
			str += String.fromCharCode(view.getUint8(offset + i));
		}
		return str;
	}
}