前面分析了这么多，还没有真正的走到download流程。这篇就去了解真正的downloader。
1. UpdateService.downloadUpdate
看来这正的worker就是最后new出来的Downloader。
downloadUpdate: function AUS_downloadUpdate(update, background) {
if (!update)
throw Cr.NS_ERROR_NULL_POINTER;
// Don‘t download the update if the update‘s version is less than the
// current application‘s version or the update‘s version is the same as the
// application‘s version and the build ID is the same as the application‘s
// build ID.
if (update.appVersion &&
(Services.vc.compare(update.appVersion, Services.appinfo.version) < 0 ||
update.buildID && update.buildID == Services.appinfo.appBuildID &&
update.appVersion == Services.appinfo.version)) {
LOG("UpdateService:downloadUpdate - canceling download of update since " +
"it is for an earlier or same application version and build ID.\n" +
"current application version: " + Services.appinfo.version + "\n" +
"update application version : " + update.appVersion + "\n" +
"current build ID: " + Services.appinfo.appBuildID + "\n" +
"update build ID : " + update.buildID);
cleanupActiveUpdate();
return STATE_NONE;
}
// If a download request is in progress vs. a download ready to resume
if (this.isDownloading) {
if (update.isCompleteUpdate == this._downloader.isCompleteUpdate &&
background == this._downloader.background) {
LOG("UpdateService:downloadUpdate - no support for downloading more " +
"than one update at a time");
return readStatusFile(getUpdatesDir());
}
this._downloader.cancel();
}
if (AppConstants.platform == "gonk") {
let um = Cc["@mozilla.org/updates/update-manager;1"].
getService(Ci.nsIUpdateManager);
let activeUpdate = um.activeUpdate;
if (activeUpdate &&
(activeUpdate.appVersion != update.appVersion ||
activeUpdate.buildID != update.buildID)) {
// We have an activeUpdate (which presumably was interrupted), and are
// about start downloading a new one. Make sure we remove all traces
// of the active one (otherwise we‘ll start appending the new update.mar
// the the one that‘s been partially downloaded).
LOG("UpdateService:downloadUpdate - removing stale active update.");
cleanupActiveUpdate();
}
}
// Set the previous application version prior to downloading the update.
update.previousAppVersion = Services.appinfo.version;
this._downloader = new Downloader(background, this);
return this._downloader.downloadUpdate(update);
},
2. Downloader.downloadUpdate
由于downloadUpdate函数比较长，这里只贴出部分代码
/**
* Download and stage the given update.
* @param update
* A nsIUpdate object to download a patch for. Cannot be null.
*/
downloadUpdate: function Downloader_downloadUpdate(update) { ... // 获取update保存位置 var updateDir = getUpdatesDir(); ... //根据预设的policy，返回Update中的一个UpdatePatch以下载 this._patch = this._selectPatch(update, updateDir); ...
// Only used by gonk
let status = STATE_NONE;
if (AppConstants.platform == "gonk") {
...
// 检测之前是否有interrupted update
} ... // 获取patch的URL var uri = Services.io.newURI(this._patch.URL, null, null); // 创建一个nsIIncrementalDownload组件去下载 this._request = Cc["@mozilla.org/network/incremental-download;1"].createInstance(Ci.nsIIncrementalDownload);
LOG("Downloader:downloadUpdate - downloading from " + uri.spec + " to " + patchFile.path);
var interval = this.background ? getPref("getIntPref",
PREF_APP_UPDATE_BACKGROUND_INTERVAL, DOWNLOAD_BACKGROUND_INTERVAL) : DOWNLOAD_FOREGROUND_INTERVAL;
this._request.init(uri, patchFile, DOWNLOAD_CHUNK_SIZE, interval);
//传递了this，因为Downloader实现了nsIRequest和nsIProcessEventSink接口，实现下载完成、下载进度等的回调
this._request.start(this, null);
writeStatusFile(updateDir, STATE_DOWNLOADING);
this._patch.QueryInterface(Ci.nsIWritablePropertyBag);
this._patch.state = STATE_DOWNLOADING;
// 通过UpdateManager保存当前的下载update
var um = Cc["@mozilla.org/updates/update-manager;1"].getService(Ci.nsIUpdateManager);
um.saveUpdates();
return STATE_DOWNLOADING;
}
3. Downloader.onStopRequest 下载完成
代码很长，贴关键部分
/**
* When data transfer ceases
* @param request
* The nsIRequest object for the transfer
* @param context
* Additional data
* @param status
* Status code containing the reason for the cessation.
*/
onStopRequest: function Downloader_onStopRequest(request, context, status) {
// 判断是否下载成功
if (Components.isSuccessCode(status)) {
// 验证update package
if (this._verifyDownload()) {
...
}
} else {
...
}
...
this._patch.state = state;
// UpdateManager保存状态
var um = Cc["@mozilla.org/updates/update-manager;1"].
getService(Ci.nsIUpdateManager);
if (deleteActiveUpdate) {
this._update.installDate = (new Date()).getTime();
um.activeUpdate = null;
}
else {
if (um.activeUpdate) {
um.activeUpdate.state = state;
}
}
um.saveUpdates();
...
if (shouldShowPrompt) {
// Notify the user that an update has been downloaded and is ready for
// installation (i.e. that they should restart the application). We do
// not notify on failed update attempts.
let prompter = Cc["@mozilla.org/updates/update-prompt;1"].
createInstance(Ci.nsIUpdatePrompt);
// 通知UpdatePrompt，update下载完成
prompter.showUpdateDownloaded(this._update, true);
}
}