b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
115 lines
3.2 KiB
JavaScript
115 lines
3.2 KiB
JavaScript
/* global FLACMetadata, ForwardLockMetadata, ID3v1Metadata, ID3v2Metadata,
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LazyLoader, MP4Metadata, OggMetadata */
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/* exported MetadataFormats */
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'use strict';
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/**
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* Delegates metadata parsing to the appropriate parser based on magic header
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* values.
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*/
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var MetadataFormats = (function() {
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/*
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* This is the list of formats that we know how to parse. Each format has
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* three properties:
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*
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* @property {String} file The path to the file for parsing this metadata
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* format.
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* @property {Object} module A getter that returns the module object for this
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* parser. Note: It *must* be a getter because it needs to be evaluated
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* *after* the file is loaded.
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* @property {Function} match A function that takes a BlobView of the file
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* and returns true if the file uses this metadata format.
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*/
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var formats = [
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{
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file: 'js/metadata/forward_lock.js',
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get module() { return ForwardLockMetadata; },
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match: function(header) {
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return header.getBinaryText(0, 9) === 'LOCKED 1 ';
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}
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},
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{
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file: 'js/metadata/id3v2.js',
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get module() { return ID3v2Metadata; },
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match: function(header) {
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return header.getBinaryText(0, 3) === 'ID3';
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}
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},
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{
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file: 'js/metadata/ogg.js',
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get module() { return OggMetadata; },
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match: function(header) {
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return header.getBinaryText(0, 4) === 'OggS';
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}
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},
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{
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file: 'js/metadata/flac.js',
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get module() { return FLACMetadata; },
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match: function(header) {
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return header.getBinaryText(0, 4) === 'fLaC';
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}
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},
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{
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file: 'js/metadata/mp4.js',
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get module() { return MP4Metadata; },
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match: function(header) {
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return header.getBinaryText(4, 4) === 'ftyp';
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}
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},
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{
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file: 'js/metadata/id3v1.js',
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get module() { return ID3v1Metadata; },
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match: function(header) {
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return (header.getUint16(0, false) & 0xFFFE) === 0xFFFA;
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}
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}
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];
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/**
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* Create a new metadata parser for a particular file format.
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*
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* @param {Object} formatInfo A description of the file format containing a
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* `file` attribute for the file to load, and a `module` attribute returning
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* the module that contains the parse() method we should call.
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*/
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function MetadataParser(formatInfo) {
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this._formatInfo = formatInfo;
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}
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MetadataParser.prototype = {
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/**
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* Parse a file and return a Promise with the metadata.
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*
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* @param {BlobView} header The file in question.
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* @return {Promise} A Promise that resolves with the completed metadata
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* object.
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*/
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parse: function(header) {
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var info = this._formatInfo;
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return LazyLoader.load(info.file).then(() => {
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return info.module.parse(header);
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});
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}
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};
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/**
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* Find the appropriate metadata parser for a given file.
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*
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* @param {BlobView} header The file in question.
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* @return {MetadataParser} The metadata parser to use for this file.
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*/
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function findParser(header) {
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for (var i = 0; i < formats.length; i++) {
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if (formats[i].match(header)) {
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return new MetadataParser(formats[i]);
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}
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}
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return null;
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}
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return {
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findParser: findParser
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};
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})();
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