Implement Ogg demuxer

src/ogg/ogg-reader.ts

@@ -0,0 +1,135 @@
+import { Reader } from '../reader';
+
+const OGGS = 0x5367674f; // 'OggS'
+export const MIN_PAGE_HEADER_SIZE = 27;
+export const MAX_PAGE_HEADER_SIZE = 27 + 255;
+export const MAX_PAGE_SIZE = MAX_PAGE_HEADER_SIZE + 255 * 255;
+
+export type Page = {
+	headerStartPos: number;
+	totalSize: number;
+	dataStartPos: number;
+	dataSize: number;
+	headerType: number;
+	granulePosition: number;
+	serialNumber: number;
+	sequenceNumber: number;
+	checksum: number;
+	lacingValues: number[];
+};
+
+export class OggReader {
+	pos = 0;
+	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);
+	}
+
+	readU8() {
+		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 1);
+		this.pos += 1;
+
+		return view.getUint8(offset);
+	}
+
+	readU32() {
+		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 4);
+		this.pos += 4;
+
+		return view.getUint32(offset, true);
+	}
+
+	readI32() {
+		const { view, offset } = this.reader.getViewAndOffset(this.pos, this.pos + 4);
+		this.pos += 4;
+
+		return view.getInt32(offset, true);
+	}
+
+	readI64() {
+		const low = this.readU32();
+		const high = this.readI32();
+		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;
+	}
+
+	readPageHeader(): Page | null {
+		const startPos = this.pos;
+
+		const capturePattern = this.readU32();
+		if (capturePattern !== OGGS) {
+			return null;
+		}
+
+		this.pos += 1; // Version
+		const headerType = this.readU8();
+		const granulePosition = this.readI64();
+		const serialNumber = this.readU32();
+		const sequenceNumber = this.readU32();
+		const checksum = this.readU32();
+
+		const numberPageSegments = this.readU8();
+		const lacingValues: number[] = [];
+
+		for (let i = 0; i < numberPageSegments; i++) {
+			lacingValues.push(this.readU8());
+		}
+
+		const headerSize = 27 + numberPageSegments;
+		const dataSize = lacingValues.reduce((a, b) => a + b, 0);
+		const totalSize = headerSize + dataSize;
+
+		return {
+			headerStartPos: startPos,
+			totalSize,
+			dataStartPos: startPos + headerSize,
+			dataSize,
+			headerType,
+			granulePosition,
+			serialNumber,
+			sequenceNumber,
+			checksum,
+			lacingValues,
+		};
+	}
+
+	findNextPageHeader(until: number) {
+		while (this.pos < until - (4 - 1)) { // Size of word minus 1
+			const word = this.readU32();
+			const firstByte = word & 0xff;
+			const secondByte = (word >>> 8) & 0xff;
+			const thirdByte = (word >>> 16) & 0xff;
+			const fourthByte = (word >>> 24) & 0xff;
+
+			const O = 0x4f; // 'O'
+			if (firstByte !== O && secondByte !== O && thirdByte !== O && fourthByte !== O) {
+				continue;
+			}
+
+			this.pos -= 4;
+
+			if (word === OGGS) {
+				// We have found the capture pattern
+				return true;
+			}
+
+			this.pos += 1;
+		}
+
+		return false;
+	}
+}