b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
115 lines
3.2 KiB
JavaScript
Executable file
115 lines
3.2 KiB
JavaScript
Executable file
/* 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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