Firefox file downloading process structure figure - firefox

Question

For my project, I need to study some info like "FireFox/Gecko file downloading structure overview"(if any), or somewhat "file downloading process flow chart of FireFox/Gecko". I couldn't find something like that in the Internet so far. Is there any info about it? Thanks a lot.
PS: It must include the paths about all file downloading through FireFox browser, which are via the network connection info APIs and file handling APIs, just like "httpOpenRequest" or "DoFileDownload" API(if any).
What would be the Firefox downloading process API paths?? Is there any figure or chart?
Please help me...

Answer 1

You are probably going to need to look at the code to get the information you desire. You will need to build the flowchart yourself.
There are a couple of different ways downloading is done in the code.
If you are talking about a Firefox add-on performing a download, then it is probably being done using Downloads.jsm (although there is an older method for doing so). The source code for that JavaScript module is at resource://gre/modules/Downloads.jsm (This URL is only valid in Firefox). There appear to be several files all located in the jsloader\resource\gre\modules directory within the zip format file called omni.ja in the root of the Firefox distribution. You can just copy that file and change the name to omni.zip and access it as a normal .zip file.
If you are wanting to know how Firefox saves a page when it is requested by the user: It is defined in the context menu with the oncommand value being gContextMenu.saveLink();. saveLink() is defined in: chrome://browser/content/nsContextMenu.js. It does some housekeeping and then calls saveHelper() which is in the same file.
The saveHelper() code is the following:
// Helper function to wait for appropriate MIME-type headers and
// then prompt the user with a file picker
saveHelper: function(linkURL, linkText, dialogTitle, bypassCache, doc) {
// canonical def in nsURILoader.h
const NS_ERROR_SAVE_LINK_AS_TIMEOUT = 0x805d0020;
// an object to proxy the data through to
// nsIExternalHelperAppService.doContent, which will wait for the
// appropriate MIME-type headers and then prompt the user with a
// file picker
function saveAsListener() {}
saveAsListener.prototype = {
extListener: null,
onStartRequest: function saveLinkAs_onStartRequest(aRequest, aContext) {
// if the timer fired, the error status will have been caused by that,
// and we'll be restarting in onStopRequest, so no reason to notify
// the user
if (aRequest.status == NS_ERROR_SAVE_LINK_AS_TIMEOUT)
return;
timer.cancel();
// some other error occured; notify the user...
if (!Components.isSuccessCode(aRequest.status)) {
try {
const sbs = Cc["#mozilla.org/intl/stringbundle;1"].
getService(Ci.nsIStringBundleService);
const bundle = sbs.createBundle(
"chrome://mozapps/locale/downloads/downloads.properties");
const title = bundle.GetStringFromName("downloadErrorAlertTitle");
const msg = bundle.GetStringFromName("downloadErrorGeneric");
const promptSvc = Cc["#mozilla.org/embedcomp/prompt-service;1"].
getService(Ci.nsIPromptService);
promptSvc.alert(doc.defaultView, title, msg);
} catch (ex) {}
return;
}
var extHelperAppSvc =
Cc["#mozilla.org/uriloader/external-helper-app-service;1"].
getService(Ci.nsIExternalHelperAppService);
var channel = aRequest.QueryInterface(Ci.nsIChannel);
this.extListener =
extHelperAppSvc.doContent(channel.contentType, aRequest,
doc.defaultView, true);
this.extListener.onStartRequest(aRequest, aContext);
},
onStopRequest: function saveLinkAs_onStopRequest(aRequest, aContext,
aStatusCode) {
if (aStatusCode == NS_ERROR_SAVE_LINK_AS_TIMEOUT) {
// do it the old fashioned way, which will pick the best filename
// it can without waiting.
saveURL(linkURL, linkText, dialogTitle, bypassCache, false,
doc.documentURIObject, doc);
}
if (this.extListener)
this.extListener.onStopRequest(aRequest, aContext, aStatusCode);
},
onDataAvailable: function saveLinkAs_onDataAvailable(aRequest, aContext,
aInputStream,
aOffset, aCount) {
this.extListener.onDataAvailable(aRequest, aContext, aInputStream,
aOffset, aCount);
}
}
function callbacks() {}
callbacks.prototype = {
getInterface: function sLA_callbacks_getInterface(aIID) {
if (aIID.equals(Ci.nsIAuthPrompt) || aIID.equals(Ci.nsIAuthPrompt2)) {
// If the channel demands authentication prompt, we must cancel it
// because the save-as-timer would expire and cancel the channel
// before we get credentials from user. Both authentication dialog
// and save as dialog would appear on the screen as we fall back to
// the old fashioned way after the timeout.
timer.cancel();
channel.cancel(NS_ERROR_SAVE_LINK_AS_TIMEOUT);
}
throw Cr.NS_ERROR_NO_INTERFACE;
}
}
// if it we don't have the headers after a short time, the user
// won't have received any feedback from their click. that's bad. so
// we give up waiting for the filename.
function timerCallback() {}
timerCallback.prototype = {
notify: function sLA_timer_notify(aTimer) {
channel.cancel(NS_ERROR_SAVE_LINK_AS_TIMEOUT);
return;
}
}
// set up a channel to do the saving
var ioService = Cc["#mozilla.org/network/io-service;1"].
getService(Ci.nsIIOService);
var channel = ioService.newChannelFromURI(makeURI(linkURL));
if (channel instanceof Ci.nsIPrivateBrowsingChannel) {
let docIsPrivate = PrivateBrowsingUtils.isWindowPrivate(doc.defaultView);
channel.setPrivate(docIsPrivate);
}
channel.notificationCallbacks = new callbacks();
let flags = Ci.nsIChannel.LOAD_CALL_CONTENT_SNIFFERS;
if (bypassCache)
flags |= Ci.nsIRequest.LOAD_BYPASS_CACHE;
if (channel instanceof Ci.nsICachingChannel)
flags |= Ci.nsICachingChannel.LOAD_BYPASS_LOCAL_CACHE_IF_BUSY;
channel.loadFlags |= flags;
if (channel instanceof Ci.nsIHttpChannel) {
channel.referrer = doc.documentURIObject;
if (channel instanceof Ci.nsIHttpChannelInternal)
channel.forceAllowThirdPartyCookie = true;
}
// fallback to the old way if we don't see the headers quickly
var timeToWait =
gPrefService.getIntPref("browser.download.saveLinkAsFilenameTimeout");
var timer = Cc["#mozilla.org/timer;1"].createInstance(Ci.nsITimer);
timer.initWithCallback(new timerCallback(), timeToWait,
timer.TYPE_ONE_SHOT);
// kick off the channel with our proxy object as the listener
channel.asyncOpen(new saveAsListener(), null);
}