mediabunny/src/misc.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/.
 */

export function assert(x: unknown): asserts x {
	if (!x) {
		throw new Error('Assertion failed.');
	}
}

/**
 * Represents a clockwise rotation in degrees.
 * @public
 */
export type Rotation = 0 | 90 | 180 | 270;

export const normalizeRotation = (rotation: number) => {
	const mappedRotation = (rotation % 360 + 360) % 360;

	if (mappedRotation === 0 || mappedRotation === 90 || mappedRotation === 180 || mappedRotation === 270) {
		return mappedRotation as Rotation;
	} else {
		throw new Error(`Invalid rotation ${rotation}.`);
	}
};

export type TransformationMatrix = [number, number, number, number, number, number, number, number, number];

export const last = <T>(arr: T[]) => {
	return arr && arr[arr.length - 1];
};

export const isU32 = (value: number) => {
	return value >= 0 && value < 2 ** 32;
};

export class Bitstream {
	/** Current offset in bits. */
	pos = 0;

	constructor(public bytes: Uint8Array) {}

	seekToByte(byteOffset: number) {
		this.pos = 8 * byteOffset;
	}

	private readBit() {
		const byteIndex = Math.floor(this.pos / 8);
		const byte = this.bytes[byteIndex] ?? 0;
		const bitIndex = 0b111 - (this.pos & 0b111);
		const bit = (byte & (1 << bitIndex)) >> bitIndex;

		this.pos++;
		return bit;
	}

	readBits(n: number) {
		if (n === 1) {
			return this.readBit();
		}

		let result = 0;

		for (let i = 0; i < n; i++) {
			result <<= 1;
			result |= this.readBit();
		}

		return result;
	}

	readAlignedByte() {
		// Ensure we're byte-aligned
		if (this.pos % 8 !== 0) {
			throw new Error('Bitstream is not byte-aligned.');
		}

		const byteIndex = this.pos / 8;
		const byte = this.bytes[byteIndex] ?? 0;

		this.pos += 8;
		return byte;
	}

	skipBits(n: number) {
		this.pos += n;
	}

	getBitsLeft() {
		return this.bytes.length * 8 - this.pos;
	}

	clone() {
		const clone = new Bitstream(this.bytes);
		clone.pos = this.pos;
		return clone;
	}
}

/** Reads an exponential-Golomb universal code from a Bitstream.  */
export const readExpGolomb = (bitstream: Bitstream) => {
	let leadingZeroBits = 0;
	while (bitstream.readBits(1) === 0 && leadingZeroBits < 32) {
		leadingZeroBits++;
	}

	if (leadingZeroBits >= 32) {
		throw new Error('Invalid exponential-Golomb code.');
	}

	const result = (1 << leadingZeroBits) - 1 + bitstream.readBits(leadingZeroBits);
	return result;
};

/** Reads a signed exponential-Golomb universal code from a Bitstream. */
export const readSignedExpGolomb = (bitstream: Bitstream) => {
	const codeNum = readExpGolomb(bitstream);

	return ((codeNum & 1) === 0)
		? -(codeNum >> 1)
		: ((codeNum + 1) >> 1);
};

export const writeBits = (bytes: Uint8Array, start: number, end: number, value: number) => {
	for (let i = start; i < end; i++) {
		const byteIndex = Math.floor(i / 8);
		let byte = bytes[byteIndex]!;
		const bitIndex = 0b111 - (i & 0b111);

		byte &= ~(1 << bitIndex);
		byte |= ((value & (1 << (end - i - 1))) >> (end - i - 1)) << bitIndex;
		bytes[byteIndex] = byte;
	}
};

export const toUint8Array = (source: AllowSharedBufferSource): Uint8Array => {
	if (source instanceof Uint8Array) {
		return source;
	} else if (source instanceof ArrayBuffer) {
		return new Uint8Array(source);
	} else {
		return new Uint8Array(source.buffer, source.byteOffset, source.byteLength);
	}
};

export const toDataView = (source: AllowSharedBufferSource) => {
	if (source instanceof DataView) {
		return source;
	} else if (source instanceof ArrayBuffer) {
		return new DataView(source);
	} else {
		return new DataView(source.buffer, source.byteOffset, source.byteLength);
	}
};

export const textEncoder = new TextEncoder();

const invertObject = <K extends PropertyKey, V extends PropertyKey>(object: Record<K, V>) => {
	return Object.fromEntries(Object.entries(object).map(([key, value]) => [value, key])) as Record<V, K>;
};

// For the color space mappings, see Rec. ITU-T H.273.

export const COLOR_PRIMARIES_MAP = {
	bt709: 1, // ITU-R BT.709
	bt470bg: 5, // ITU-R BT.470BG
	smpte170m: 6, // ITU-R BT.601 525 - SMPTE 170M
	bt2020: 9, // ITU-R BT.202
	smpte432: 12, // SMPTE EG 432-1
};
export const COLOR_PRIMARIES_MAP_INVERSE = invertObject(COLOR_PRIMARIES_MAP);

export const TRANSFER_CHARACTERISTICS_MAP = {
	'bt709': 1, // ITU-R BT.709
	'smpte170m': 6, // SMPTE 170M
	'linear': 8, // Linear transfer characteristics
	'iec61966-2-1': 13, // IEC 61966-2-1
	'pg': 16, // Rec. ITU-R BT.2100-2 perceptual quantization (PQ) system
	'hlg': 18, // Rec. ITU-R BT.2100-2 hybrid loggamma (HLG) system
};
export const TRANSFER_CHARACTERISTICS_MAP_INVERSE = invertObject(TRANSFER_CHARACTERISTICS_MAP);

export const MATRIX_COEFFICIENTS_MAP = {
	'rgb': 0, // Identity
	'bt709': 1, // ITU-R BT.709
	'bt470bg': 5, // ITU-R BT.470BG
	'smpte170m': 6, // SMPTE 170M
	'bt2020-ncl': 9, // ITU-R BT.2020-2 (non-constant luminance)
};
export const MATRIX_COEFFICIENTS_MAP_INVERSE = invertObject(MATRIX_COEFFICIENTS_MAP);

export type RequiredNonNull<T> = {
	[K in keyof T]-?: NonNullable<T[K]>;
};

export const colorSpaceIsComplete = (
	colorSpace: VideoColorSpaceInit | undefined,
): colorSpace is RequiredNonNull<VideoColorSpaceInit> => {
	return (
		!!colorSpace
		&& !!colorSpace.primaries
		&& !!colorSpace.transfer
		&& !!colorSpace.matrix
		&& colorSpace.fullRange !== undefined
	);
};

export const isAllowSharedBufferSource = (x: unknown) => {
	return (
		x instanceof ArrayBuffer
		|| (typeof SharedArrayBuffer !== 'undefined' && x instanceof SharedArrayBuffer)
		|| ArrayBuffer.isView(x)
	);
};

export class AsyncMutex {
	currentPromise = Promise.resolve();

	async acquire() {
		let resolver: () => void;
		const nextPromise = new Promise<void>((resolve) => {
			resolver = resolve;
		});

		const currentPromiseAlias = this.currentPromise;
		this.currentPromise = nextPromise;

		await currentPromiseAlias;

		return resolver!;
	}
}

export const bytesToHexString = (bytes: Uint8Array) => {
	return [...bytes].map(x => x.toString(16).padStart(2, '0')).join('');
};

export const reverseBitsU32 = (x: number): number => {
	x = ((x >> 1) & 0x55555555) | ((x & 0x55555555) << 1);
	x = ((x >> 2) & 0x33333333) | ((x & 0x33333333) << 2);
	x = ((x >> 4) & 0x0f0f0f0f) | ((x & 0x0f0f0f0f) << 4);
	x = ((x >> 8) & 0x00ff00ff) | ((x & 0x00ff00ff) << 8);
	x = ((x >> 16) & 0x0000ffff) | ((x & 0x0000ffff) << 16);
	return x >>> 0; // Ensure it's treated as an unsigned 32-bit integer
};

/** Returns the smallest index i such that val[i] === key, or -1 if no such index exists. */
export const binarySearchExact = <T>(arr: T[], key: number, valueGetter: (x: T) => number): number => {
	let low = 0;
	let high = arr.length - 1;
	let ans = -1;

	while (low <= high) {
		const mid = (low + high) >> 1;
		const midVal = valueGetter(arr[mid]!);

		if (midVal === key) {
			ans = mid;
			high = mid - 1; // Continue searching left to find the lowest index
		} else if (midVal < key) {
			low = mid + 1;
		} else {
			high = mid - 1;
		}
	}

	return ans;
};

/** Returns the largest index i such that val[i] <= key, or -1 if no such index exists. */
export const binarySearchLessOrEqual = <T>(arr: T[], key: number, valueGetter: (x: T) => number) => {
	let low = 0;
	let high = arr.length - 1;
	let ans = -1;

	while (low <= high) {
		const mid = (low + (high - low + 1) / 2) | 0;
		const midVal = valueGetter(arr[mid]!);

		if (midVal <= key) {
			ans = mid;
			low = mid + 1;
		} else {
			high = mid - 1;
		}
	}

	return ans;
};

/** Assumes the array is already sorted. */
export const insertSorted = <T>(arr: T[], item: T, valueGetter: (x: T) => number) => {
	const insertionIndex = binarySearchLessOrEqual(arr, valueGetter(item), valueGetter);
	arr.splice(insertionIndex + 1, 0, item); // This even behaves correctly for the -1 case
};

export const promiseWithResolvers = <T = void>() => {
	let resolve: (value: T) => void;
	let reject: (reason: unknown) => void;
	const promise = new Promise<T>((res, rej) => {
		resolve = res;
		reject = rej;
	});

	return { promise, resolve: resolve!, reject: reject! };
};

export const removeItem = <T>(arr: T[], item: T) => {
	const index = arr.indexOf(item);
	if (index !== -1) {
		arr.splice(index, 1);
	}
};

export const findLast = <T>(arr: T[], predicate: (x: T) => boolean) => {
	for (let i = arr.length - 1; i >= 0; i--) {
		if (predicate(arr[i]!)) {
			return arr[i];
		}
	}

	return undefined;
};

export const findLastIndex = <T>(arr: T[], predicate: (x: T) => boolean) => {
	for (let i = arr.length - 1; i >= 0; i--) {
		if (predicate(arr[i]!)) {
			return i;
		}
	}

	return -1;
};

/**
 * Sync or async iterable.
 * @public
 */
export type AnyIterable<T> =
	| Iterable<T>
	| AsyncIterable<T>;

export const toAsyncIterator = async function* <T>(source: AnyIterable<T>): AsyncGenerator<T, void, unknown> {
	if (Symbol.iterator in source) {
		// @ts-expect-error Trust me
		yield* source[Symbol.iterator]();
	} else {
		// @ts-expect-error Trust me
		yield* source[Symbol.asyncIterator]();
	}
};

export const validateAnyIterable = (iterable: AnyIterable<unknown>) => {
	if (!(Symbol.iterator in iterable) && !(Symbol.asyncIterator in iterable)) {
		throw new TypeError('Argument must be an iterable or async iterable.');
	}
};

export const assertNever = (x: never) => {
	// eslint-disable-next-line @typescript-eslint/restrict-template-expressions
	throw new Error(`Unexpected value: ${x}`);
};

export const getUint24 = (view: DataView, byteOffset: number, littleEndian: boolean) => {
	const byte1 = view.getUint8(byteOffset);
	const byte2 = view.getUint8(byteOffset + 1);
	const byte3 = view.getUint8(byteOffset + 2);

	if (littleEndian) {
		return byte1 | (byte2 << 8) | (byte3 << 16);
	} else {
		return (byte1 << 16) | (byte2 << 8) | byte3;
	}
};

export const getInt24 = (view: DataView, byteOffset: number, littleEndian: boolean) => {
	// The left shift pushes the most significant bit into the sign bit region, and the subsequent right shift
	// then correctly interprets the sign bit.
	return getUint24(view, byteOffset, littleEndian) << 8 >> 8;
};

export const setUint24 = (view: DataView, byteOffset: number, value: number, littleEndian: boolean) => {
	// Ensure the value is within 24-bit unsigned range (0 to 16777215)
	value = value >>> 0; // Convert to unsigned 32-bit
	value = value & 0xFFFFFF; // Mask to 24 bits

	if (littleEndian) {
		view.setUint8(byteOffset, value & 0xFF);
		view.setUint8(byteOffset + 1, (value >>> 8) & 0xFF);
		view.setUint8(byteOffset + 2, (value >>> 16) & 0xFF);
	} else {
		view.setUint8(byteOffset, (value >>> 16) & 0xFF);
		view.setUint8(byteOffset + 1, (value >>> 8) & 0xFF);
		view.setUint8(byteOffset + 2, value & 0xFF);
	}
};

export const setInt24 = (view: DataView, byteOffset: number, value: number, littleEndian: boolean) => {
	// Ensure the value is within 24-bit signed range (-8388608 to 8388607)
	value = clamp(value, -8388608, 8388607);

	// Convert negative values to their 24-bit representation
	if (value < 0) {
		value = (value + 0x1000000) & 0xFFFFFF;
	}

	setUint24(view, byteOffset, value, littleEndian);
};

export const setInt64 = (view: DataView, byteOffset: number, value: number, littleEndian: boolean) => {
	if (littleEndian) {
		view.setUint32(byteOffset + 0, value, true);
		view.setInt32(byteOffset + 4, Math.floor(value / 2 ** 32), true);
	} else {
		view.setInt32(byteOffset + 0, Math.floor(value / 2 ** 32), true);
		view.setUint32(byteOffset + 4, value, true);
	}
};

/**
 * Calls a function on each value spat out by an async generator. The reason for writing this manually instead of
 * using a generator function is that the generator function queues return() calls - here, we forward them immediately.
 */
export const mapAsyncGenerator = <T, U>(
	generator: AsyncGenerator<T, void, unknown>,
	map: (t: T) => U,
): AsyncGenerator<U, void, unknown> => {
	return {
		async next() {
			const result = await generator.next();
			if (result.done) {
				return { value: undefined, done: true };
			} else {
				return { value: map(result.value), done: false };
			}
		},
		return() {
			return generator.return() as ReturnType<AsyncGenerator<U, void, unknown>['return']>;
		},
		throw(error) {
			return generator.throw(error) as ReturnType<AsyncGenerator<U, void, unknown>['throw']>;
		},
		[Symbol.asyncIterator]() {
			return this;
		},
	};
};

export const clamp = (value: number, min: number, max: number) => {
	return Math.max(min, Math.min(max, value));
};

export const UNDETERMINED_LANGUAGE = 'und';

export const roundToPrecision = (value: number, digits: number) => {
	const factor = 10 ** digits;
	return Math.round(value * factor) / factor;
};

export const roundToMultiple = (value: number, multiple: number) => {
	return Math.round(value / multiple) * multiple;
};

export const ilog = (x: number) => {
	let ret = 0;
	while (x) {
		ret++;
		x >>= 1;
	}
	return ret;
};

const ISO_639_2_REGEX = /^[a-z]{3}$/;
export const isIso639Dash2LanguageCode = (x: string) => {
	return ISO_639_2_REGEX.test(x);
};

// Since the result will be truncated, add a bit of eps to compensate for floating point errors
export const SECOND_TO_MICROSECOND_FACTOR = 1e6 * (1 + Number.EPSILON);

/**
 * Sets all keys K of T to be required.
 * @public
 */
export type SetRequired<T, K extends keyof T> = T & Required<Pick<T, K>>;

export const mergeObjectsDeeply = <T extends object, S extends object>(a: T, b: S): T & S => {
	const result = { ...a } as T & S;

	for (const key in b) {
		if (
			typeof a[key as unknown as keyof T] === 'object'
			&& a[key as unknown as keyof T] !== null
			&& typeof b[key] === 'object'
			&& b[key] !== null
		) {
			result[key] = mergeObjectsDeeply(
				a[key as unknown as keyof T] as object,
				b[key],
			) as (T & S)[Extract<keyof S, string>];
		} else {
			result[key] = b[key] as (T & S)[Extract<keyof S, string>];
		}
	}

	return result;
};

export const retriedFetch = async (
	url: string | URL,
	requestInit: RequestInit,
	getRetryDelay: (previousAttempts: number) => number | null,
) => {
	let attempts = 0;

	while (true) {
		try {
			return await fetch(url, requestInit);
		} catch (error) {
			attempts++;
			const retryDelayInSeconds = getRetryDelay(attempts);

			if (retryDelayInSeconds === null) {
				throw error;
			}

			console.error('Retrying failed fetch. Error:', error);

			if (!Number.isFinite(retryDelayInSeconds) || retryDelayInSeconds < 0) {
				throw new TypeError('Retry delay must be a non-negative finite number.');
			}

			if (retryDelayInSeconds > 0) {
				await new Promise(resolve => setTimeout(resolve, 1000 * retryDelayInSeconds));
			}
		}
	}
};

export const computeRationalApproximation = (x: number, maxDenominator: number) => {
	// Handle negative numbers
	const sign = x < 0 ? -1 : 1;
	x = Math.abs(x);

	let prevNumerator = 0, prevDenominator = 1;
	let currNumerator = 1, currDenominator = 0;

	// Continued fraction algorithm
	let remainder = x;

	while (true) {
		const integer = Math.floor(remainder);

		// Calculate next convergent
		const nextNumerator = integer * currNumerator + prevNumerator;
		const nextDenominator = integer * currDenominator + prevDenominator;

		if (nextDenominator > maxDenominator) {
			return {
				numerator: sign * currNumerator,
				denominator: currDenominator,
			};
		}

		prevNumerator = currNumerator;
		prevDenominator = currDenominator;
		currNumerator = nextNumerator;
		currDenominator = nextDenominator;

		remainder = 1 / (remainder - integer);

		// Guard against precision issues
		if (!isFinite(remainder)) {
			break;
		}
	}

	return {
		numerator: sign * currNumerator,
		denominator: currDenominator,
	};
};

export class CallSerializer {
	currentPromise = Promise.resolve();

	call(fn: () => Promise<void> | void) {
		return this.currentPromise = this.currentPromise.then(fn);
	}
}

let isSafariCache: boolean | null = null;
export const isSafari = () => {
	if (isSafariCache !== null) {
		return isSafariCache;
	}

	const result = !!(
		typeof navigator !== 'undefined'
		&& navigator.vendor?.match(/apple/i)
		&& !navigator.userAgent?.match(/crios/i)
		&& !navigator.userAgent?.match(/fxios/i)
		&& !navigator.userAgent?.match(/Opera|OPT\//)
	);

	isSafariCache = result;
	return result;
};

/**
 * T or a promise that resolves to T.
 * @public
 */
export type MaybePromise<T> = T | Promise<T>;