read and write strings from arraybuffers

StringView.js

function strlen(buffer, byteOffset, byteLength) {
	let array = new Uint8Array(buffer, byteOffset, byteLength);
	
	for (let i = 0; i < array.length; i++) {
		if (array[i] == 0)
			return i;
	}
	
	throw new Error("invalid string: not ending with null byte");
}

class StringView {
	constructor(buffer, byteOffset = 0, byteLength = null) {
		this.buffer = buffer;
		this.byteOffset = byteOffset;
		this.byteLength = byteLength === null ? buffer.byteLength : byteLength;
	}
	
	getString(byteOffset = 0, encoding = "utf-8") {
		let length = strlen(this.buffer, this.byteOffset+byteOffset, this.byteLength-byteOffset);
		
		let bytes = new DataView(this.buffer, this.byteOffset+byteOffset, length);
		return new TextDecoder(encoding).decode(bytes);
	}
	
	setString(value, byteOffset = 0, encoding = "utf-8") {
		if (encoding != "utf-8") throw new Error("only utf-8 is supported at the moment");
		
		let array = new Uint8Array(this.buffer, this.byteOffset, this.byteLength);

		let bytes = new TextEncoder().encode(value);

		let nullpos = byteOffset+bytes.byteLength;
		if (nullpos >= array.length)
			throw new RangeError("String too long");
		
		array.set(bytes, byteOffset);
		array[nullpos] = 0;
		return bytes.byteLength+1;
	}
}

let buffer = new ArrayBuffer(20);
let array = new Uint8Array(buffer);
let view = new StringView(buffer);

let bytesWritten = view.setString("Hello World");
view.setString("Foo Bar", bytesWritten);

console.log(array);

console.log(view.getString());
console.log(view.getString(bytesWritten));