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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Webworker spec says that the worker global object is called self. That's
// a terrible name since we use it all over the chrome codebase to capture
// the 'this' keyword in lambdas.
var global = self;
// All of these scripts could be imported with a single call to importScripts,
// but then load and compile time errors would all be reported from the same
// line.
importScripts('metadata_parser.js');
importScripts('byte_reader.js');
/**
* Dispatches metadata requests to the correct parser.
*/
function MetadataDispatcher() {
importScripts('exif_parser.js');
importScripts('mpeg_parser.js');
importScripts('id3_parser.js');
var patterns = [];
for (var i = 0; i < MetadataDispatcher.parserClasses_.length; i++) {
var parserClass = MetadataDispatcher.parserClasses_[i];
this.log('new parser: ' + parserClass.parserType);
var parser = new parserClass(this);
this.parserInstances_.push(parser);
patterns.push(parser.urlFilter.source);
}
this.parserRegexp_ = new RegExp('(' + patterns.join('|') + ')', 'i');
}
MetadataDispatcher.parserClasses_ = [];
MetadataDispatcher.registerParserClass = function(parserClass) {
MetadataDispatcher.parserClasses_.push(parserClass);
};
MetadataDispatcher.prototype.parserInstances_ = [];
/**
* Verbose logging for the dispatcher.
*
* Individual parsers also take this as their default verbosity setting.
*/
MetadataDispatcher.prototype.verbose = false;
MetadataDispatcher.prototype.messageHandlers = {
init: function() {
this.postMessage('filter', [this.parserRegexp_]);
this.log('initialized with URL filter ' + this.parserRegexp_);
},
request: function(fileURL) {
var self = this;
try {
this.processOneFile(fileURL, function callback(metadata) {
self.postMessage('result', [fileURL, metadata]);
});
} catch (ex) {
this.error(ex);
}
}
};
/**
* Indicate to the caller that an operation has failed.
*
* No other messages relating to the failed operation should be sent.
*/
MetadataDispatcher.prototype.error = function(var_args) {
var ary = Array.apply(null, arguments);
this.postMessage('error', ary);
};
/**
* Send a log message to the caller.
*
* Callers must not parse log messages for control flow.
*/
MetadataDispatcher.prototype.log = function(var_args) {
var ary = Array.apply(null, arguments);
this.postMessage('log', ary);
};
/**
* Send a log message to the caller only if this.verbose is true.
*/
MetadataDispatcher.prototype.vlog = function(var_args) {
if (this.verbose)
this.log.apply(this, arguments);
};
/**
* Post a properly formatted message to the caller.
*/
MetadataDispatcher.prototype.postMessage = function(verb, arguments) {
global.postMessage({verb: verb, arguments: arguments});
};
MetadataDispatcher.prototype.onMessage = function(event) {
var data = event.data;
if (this.messageHandlers.hasOwnProperty(data.verb)) {
this.messageHandlers[data.verb].apply(this, data.arguments);
} else {
this.log('Unknown message from client: ' + data.verb, data);
}
};
MetadataDispatcher.prototype.processOneFile = function(fileURL, callback) {
var self = this;
var currentStep = -1;
function nextStep(var_args) {
self.vlog('nextStep: ' + steps[currentStep + 1].name);
steps[++currentStep].apply(self, arguments);
}
function onError(err, stepName) {
self.error(fileURL, stepName || steps[currentStep].name, err);
}
var steps =
[ // Step one, find the parser matching the url.
function detectFormat() {
for (var i = 0; i != self.parserInstances_.length; i++) {
var parser = self.parserInstances_[i];
if (fileURL.match(parser.urlFilter)) {
nextStep(parser);
return;
}
}
onError('unsupported format');
},
// Step two, turn the url into an entry.
function getEntry(parser) {
webkitResolveLocalFileSystemURL(
fileURL,
function(entry) { nextStep(entry, parser) },
onError);
},
// Step three, turn the entry into a file.
function getFile(entry, parser) {
entry.file(function(file) { nextStep(file, parser) }, onError);
},
// Step four, parse the file content.
function parseContent(file, parser) {
parser.parse(file, callback, onError);
}
];
nextStep();
};
var dispatcher = new MetadataDispatcher();
global.onmessage = dispatcher.onMessage.bind(dispatcher);
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