Borewit
82 lines
3.2 KiB
TypeScript
82 lines
3.2 KiB
TypeScript
import initDebug from 'debug';
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import * as AtomToken from './AtomToken.js';
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import { ITokenizer } from 'strtok3/core';
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export type AtomDataHandler = (atom: Atom, remaining: number) => Promise<void>;
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const debug = initDebug('music-metadata:parser:MP4:Atom');
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export class Atom {
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public static async readAtom(tokenizer: ITokenizer, dataHandler: AtomDataHandler, parent: Atom, remaining: number): Promise<Atom> {
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// Parse atom header
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const offset = tokenizer.position;
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// debug(`Reading next token on offset=${offset}...`); // buf.toString('ascii')
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const header = await tokenizer.readToken<AtomToken.IAtomHeader>(AtomToken.Header);
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const extended = header.length === BigInt(1);
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if (extended) {
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header.length = await tokenizer.readToken<bigint>(AtomToken.ExtendedSize);
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}
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const atomBean = new Atom(header, header.length === BigInt(1), parent);
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const payloadLength = atomBean.getPayloadLength(remaining);
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debug(`parse atom name=${atomBean.atomPath}, extended=${atomBean.extended}, offset=${offset}, len=${atomBean.header.length}`); // buf.toString('ascii')
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await atomBean.readData(tokenizer, dataHandler, payloadLength);
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return atomBean;
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}
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public readonly children: Atom[];
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public readonly atomPath: string;
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public constructor(public readonly header: AtomToken.IAtomHeader, public extended: boolean, public readonly parent: Atom) {
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this.children = [];
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this.atomPath = (this.parent ? this.parent.atomPath + '.' : '') + this.header.name;
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}
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public getHeaderLength(): number {
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return this.extended ? 16 : 8;
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}
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public getPayloadLength(remaining: number): number {
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return (this.header.length === BigInt(0) ? remaining : Number(this.header.length)) - this.getHeaderLength();
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}
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public async readAtoms(tokenizer: ITokenizer, dataHandler: AtomDataHandler, size: number): Promise<void> {
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while (size > 0) {
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const atomBean = await Atom.readAtom(tokenizer, dataHandler, this, size);
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this.children.push(atomBean);
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size -= atomBean.header.length === BigInt(0) ? size : Number(atomBean.header.length);
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}
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}
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private async readData(tokenizer: ITokenizer, dataHandler: AtomDataHandler, remaining: number): Promise<void> {
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switch (this.header.name) {
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// "Container" atoms, contains nested atoms
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case 'moov': // The Movie Atom: contains other atoms
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case 'udta': // User defined atom
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case 'trak':
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case 'mdia': // Media atom
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case 'minf': // Media Information Atom
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case 'stbl': // The Sample Table Atom
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case '<id>':
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case 'ilst':
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case 'tref':
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return this.readAtoms(tokenizer, dataHandler, this.getPayloadLength(remaining));
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case 'meta': // Metadata Atom, ref: https://developer.apple.com/library/content/documentation/QuickTime/QTFF/Metadata/Metadata.html#//apple_ref/doc/uid/TP40000939-CH1-SW8
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// meta has 4 bytes of padding, ignore
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await tokenizer.ignore(4);
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return this.readAtoms(tokenizer, dataHandler, this.getPayloadLength(remaining) - 4);
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case 'mdhd': // Media header atom
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case 'mvhd': // 'movie' => 'mvhd': movie header atom; child of Movie Atom
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case 'tkhd':
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case 'stsz':
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case 'mdat':
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default:
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return dataHandler(this, remaining);
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}
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}
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}
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