js.mjs

/** @typedef {Uint8Array|Int8Array|Uint8ClampedArray} TypedArray8 */
/** @typedef {Uint16Array|Int16Array} TypedArray16 */
/** @typedef {Uint32Array|Int32Array|Float32Array} TypedArray32 */
/** @typedef {BigInt64Array|BigUint64Array|Float64Array} TypedArray64 */

export default bswapJS;
export const native = undefined;
export const ise = "JS";
export const js = bswapJS;

/** @param {TypedArray8|TypedArray16|TypedArray32|TypedArray64} arr */
function bswapJS(arr) {
	if (ArrayBuffer.isView(arr)) {
		switch (arr.BYTES_PER_ELEMENT) {
			case 1:
				// no op
				return;
			case 2:
				return flip16(arr);
			case 4:
				return flip32(arr);
			case 8:
				return flip64(arr);
			default:
				throw new Error("Invalid input");
		}
	} else {
		throw new TypeError("expected typed array");
	}
}

/** @param {TypedArray16} */
function flip16(info) {
	const flipper = new Uint8Array(info.buffer, info.byteOffset, info.length * 2);
	const len = flipper.length;
	for (let i = 0; i < len; i += 2) {
		let t = flipper[i];
		flipper[i] = flipper[i + 1];
		flipper[i + 1] = t;
	}
}

/** @param {TypedArray32} */
function flip32(info) {
	const flipper = new Uint8Array(info.buffer, info.byteOffset, info.length * 4);
	const len = flipper.length;
	for (let i = 0; i < len; i += 4) {
		let t = flipper[i];
		flipper[i] = flipper[i + 3];
		flipper[i + 3] = t;
		t = flipper[i + 1];
		flipper[i + 1] = flipper[i + 2];
		flipper[i + 2] = t;
	}
}

/** @param {TypedArray64} */
function flip64(info) {
	const flipper = new Uint8Array(info.buffer, info.byteOffset, info.length * 8);
	const len = flipper.length;
	for (let i = 0; i < len; i += 8) {
		let t = flipper[i];
		flipper[i] = flipper[i + 7];
		flipper[i + 7] = t;
		t = flipper[i + 1];
		flipper[i + 1] = flipper[i + 6];
		flipper[i + 6] = t;
		t = flipper[i + 2];
		flipper[i + 2] = flipper[i + 5];
		flipper[i + 5] = t;
		t = flipper[i + 3];
		flipper[i + 3] = flipper[i + 4];
		flipper[i + 4] = t;
	}
}