Allow all Matroska AttachedFiles to be read & written via metadata tags

src/matroska/ebml.ts

@@ -16,6 +16,7 @@ export interface EBMLElement {
 	size?: number;
 	data:
 		| number
+		| bigint
 		| string
 		| Uint8Array
 		| EBMLFloat32
@@ -198,6 +199,26 @@ export const measureUnsignedInt = (value: number) => {
 	}
 };
 
+export const measureUnsignedBigInt = (value: bigint) => {
+	if (value < (1n << 8n)) {
+		return 1;
+	} else if (value < (1n << 16n)) {
+		return 2;
+	} else if (value < (1n << 24n)) {
+		return 3;
+	} else if (value < (1n << 32n)) {
+		return 4;
+	} else if (value < (1n << 40n)) {
+		return 5;
+	} else if (value < (1n << 48n)) {
+		return 6;
+	} else if (value < (1n << 56n)) {
+		return 7;
+	} else {
+		return 8;
+	}
+};
+
 export const measureSignedInt = (value: number) => {
 	if (value >= -(1 << 6) && value < (1 << 6)) {
 		return 1;
@@ -276,16 +297,16 @@ export class EBMLWriter {
 			// eslint-disable-next-line no-fallthrough
 			case 5:
 				this.helperView.setUint8(pos++, (value / 2 ** 32) | 0);
-				// eslint-disable-next-line no-fallthrough
+			// eslint-disable-next-line no-fallthrough
 			case 4:
 				this.helperView.setUint8(pos++, value >> 24);
-				// eslint-disable-next-line no-fallthrough
+			// eslint-disable-next-line no-fallthrough
 			case 3:
 				this.helperView.setUint8(pos++, value >> 16);
-				// eslint-disable-next-line no-fallthrough
+			// eslint-disable-next-line no-fallthrough
 			case 2:
 				this.helperView.setUint8(pos++, value >> 8);
-				// eslint-disable-next-line no-fallthrough
+			// eslint-disable-next-line no-fallthrough
 			case 1:
 				this.helperView.setUint8(pos++, value);
 				break;
@@ -296,6 +317,16 @@ export class EBMLWriter {
 		this.writer.write(this.helper.subarray(0, pos));
 	}
 
+	writeUnsignedBigInt(value: bigint, width = measureUnsignedBigInt(value)) {
+		let pos = 0;
+
+		for (let i = width - 1; i >= 0; i--) {
+			this.helperView.setUint8(pos++, Number((value >> BigInt(i * 8)) & 0xffn));
+		}
+
+		this.writer.write(this.helper.subarray(0, pos));
+	}
+
 	writeSignedInt(value: number, width = measureSignedInt(value)) {
 		if (value < 0) {
 			// Two's complement stuff
@@ -398,6 +429,10 @@ export class EBMLWriter {
 				const size = data.size ?? measureUnsignedInt(data.data);
 				this.writeVarInt(size);
 				this.writeUnsignedInt(data.data, size);
+			} else if (typeof data.data === 'bigint') {
+				const size = data.size ?? measureUnsignedBigInt(data.data);
+				this.writeVarInt(size);
+				this.writeUnsignedBigInt(data.data, size);
 			} else if (typeof data.data === 'string') {
 				this.writeVarInt(data.data.length);
 				this.writeAsciiString(data.data);
@@ -491,6 +526,21 @@ export const readUnsignedInt = (slice: FileSlice, width: number) => {
 	return value;
 };
 
+export const readUnsignedBigInt = (slice: FileSlice, width: number) => {
+	if (width < 1) {
+		throw new Error('Bad unsigned int size ' + width);
+	}
+
+	let value = 0n;
+
+	for (let i = 0; i < width; i++) {
+		value <<= 8n;
+		value += BigInt(readU8(slice));
+	}
+
+	return value;
+};
+
 export const readSignedInt = (slice: FileSlice, width: number) => {
 	let value = readUnsignedInt(slice, width);