/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at
http://mozilla.org/MPL/2.0/. */
/**
* Main implementation of the Downloads API objects. Consumers should get
* references to these objects through the "Downloads.sys.mjs" module.
*/
import { Integration } from "resource://gre/modules/Integration.sys.mjs";
import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
const lazy = {};
ChromeUtils.defineESModuleGetters(lazy, {
DownloadHistory: "resource://gre/modules/DownloadHistory.sys.mjs",
DownloadPaths: "resource://gre/modules/DownloadPaths.sys.mjs",
E10SUtils: "resource://gre/modules/E10SUtils.sys.mjs",
FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
NetUtil: "resource://gre/modules/NetUtil.sys.mjs",
});
XPCOMUtils.defineLazyServiceGetter(
lazy,
"gExternalAppLauncher",
"@mozilla.org/uriloader/external-helper-app-service;1",
Ci.nsPIExternalAppLauncher
);
XPCOMUtils.defineLazyServiceGetter(
lazy,
"gExternalHelperAppService",
"@mozilla.org/uriloader/external-helper-app-service;1",
Ci.nsIExternalHelperAppService
);
Integration.downloads.defineESModuleGetter(
lazy,
"DownloadIntegration",
"resource://gre/modules/DownloadIntegration.sys.mjs"
);
const BackgroundFileSaverStreamListener = Components.Constructor(
"@mozilla.org/network/background-file-saver;1?mode=streamlistener",
"nsIBackgroundFileSaver"
);
/**
* Returns true if the given value is a primitive string or a String object.
*/
function isString(aValue) {
// We cannot use the "instanceof" operator reliably across module boundaries.
return (
typeof aValue == "string" ||
(typeof aValue == "object" && "charAt" in aValue)
);
}
/**
* Serialize the unknown properties of aObject into aSerializable.
*/
function serializeUnknownProperties(aObject, aSerializable) {
if (aObject._unknownProperties) {
for (let property in aObject._unknownProperties) {
aSerializable[property] = aObject._unknownProperties[property];
}
}
}
/**
* Check for any unknown properties in aSerializable and preserve those in the
* _unknownProperties field of aObject. aFilterFn is called for each property
* name of aObject and should return true only for unknown properties.
*/
function deserializeUnknownProperties(aObject, aSerializable, aFilterFn) {
for (let property in aSerializable) {
if (aFilterFn(property)) {
if (!aObject._unknownProperties) {
aObject._unknownProperties = {};
}
aObject._unknownProperties[property] = aSerializable[property];
}
}
}
/**
* Check if the file is a placeholder.
*
* @return {Promise}
* @resolves {boolean}
* @rejects Never.
*/
async function isPlaceholder(path) {
try {
if ((await IOUtils.stat(path)).size == 0) {
return true;
}
} catch (ex) {
// Canceling the download may have removed the placeholder already.
if (ex.name != "NotFoundError") {
console.error(ex);
}
}
return false;
}
/**
* This determines the minimum time interval between updates to the number of
* bytes transferred, and is a limiting factor to the sequence of readings used
* in calculating the speed of the download.
*/
const kProgressUpdateIntervalMs = 400;
/**
* Represents a single download, with associated state and actions. This object
* is transient, though it can be included in a DownloadList so that it can be
* managed by the user interface and persisted across sessions.
*/
export var Download = function () {
this._deferSucceeded = Promise.withResolvers();
};
Download.prototype = {
/**
* DownloadSource object associated with this download.
*/
source: null,
/**
* DownloadTarget object associated with this download.
*/
target: null,
/**
* DownloadSaver object associated with this download.
*/
saver: null,
/**
* Indicates that the download never started, has been completed successfully,
* failed, or has been canceled. This property becomes false when a download
* is started for the first time, or when a failed or canceled download is
* restarted.
*/
stopped: true,
/**
* Indicates that the download has been completed successfully.
*/
succeeded: false,
/**
* Indicates that the download has been canceled. This property can become
* true, then it can be reset to false when a canceled download is restarted.
*
* This property becomes true as soon as the "cancel" method is called, though
* the "stopped" property might remain false until the cancellation request
* has been processed. Temporary files or part files may still exist even if
* they are expected to be deleted, until the "stopped" property becomes true.
*/
canceled: false,
/**
* Downloaded files can be deleted from within Firefox, e.g. via the context
* menu. Currently Firefox does not track file moves (see bug 1746386), so if
* a download's target file stops existing we have to assume it's "moved or
* missing." To distinguish files intentionally deleted within Firefox from
* files that are moved/missing, we mark them as "deleted" with this property.
*/
deleted: false,
/**
* When the download fails, this is set to a DownloadError instance indicating
* the cause of the failure. If the download has been completed successfully
* or has been canceled, this property is null. This property is reset to
* null when a failed download is restarted.
*/
error: null,
/**
* Indicates the start time of the download. When the download starts,
* this property is set to a valid Date object. The default value is null
* before the download starts.
*/
startTime: null,
/**
* Indicates whether this download's "progress" property is able to report
* partial progress while the download proceeds, and whether the value in
* totalBytes is relevant. This depends on the saver and the download source.
*/
hasProgress: false,
/**
* Progress percent, from 0 to 100. Intermediate values are reported only if
* hasProgress is true.
*
* @note You shouldn't rely on this property being equal to 100 to determine
* whether the download is completed. You should use the individual
* state properties instead.
*/
progress: 0,
/**
* When hasProgress is true, indicates the total number of bytes to be
* transferred before the download finishes, that can be zero for empty files.
*
* When hasProgress is false, this property is always zero.
*
* @note This property may be different than the final file size on disk for
* downloads that are encoded during the network transfer. You can use
* the "size" property of the DownloadTarget object to get the actual
* size on disk once the download succeeds.
*/
totalBytes: 0,
/**
* Number of bytes currently transferred. This value starts at zero, and may
* be updated regardless of the value of hasProgress.
*
* @note You shouldn't rely on this property being equal to totalBytes to
* determine whether the download is completed. You should use the
* individual state properties instead. This property may not be
* updated during the last part of the download.
*/
currentBytes: 0,
/**
* Fractional number representing the speed of the download, in bytes per
* second. This value is zero when the download is stopped, and may be
* updated regardless of the value of hasProgress.
*/
speed: 0,
/**
* Indicates whether, at this time, there is any partially downloaded data
* that can be used when restarting a failed or canceled download.
*
* Even if the download has partial data on disk, hasPartialData will be false
* if that data cannot be used to restart the download. In order to determine
* if a part file is being used which contains partial data the
* Download.target.partFilePath should be checked.
*
* This property is relevant while the download is in progress, and also if it
* failed or has been canceled. If the download has been completed
* successfully, this property is always false.
*
* Whether partial data can actually be retained depends on the saver and the
* download source, and may not be known before the download is started.
*/
hasPartialData: false,
/**
* Indicates whether, at this time, there is any data that has been blocked.
* Since reputation blocking takes place after the download has fully
* completed a value of true also indicates 100% of the data is present.
*/
hasBlockedData: false,
/**
* This can be set to a function that is called after other properties change.
*/
onchange: null,
/**
* This tells if the user has chosen to open/run the downloaded file after
* download has completed.
*/
launchWhenSucceeded: false,
/**
* When a download starts, we typically want to automatically open the
* downloads panel if the pref browser.download.alwaysOpenPanel is enabled.
* However, there are conditions where we want to prevent this. For example, a
* false value can prevent the downloads panel from opening when an add-on
* creates a download without user input as part of some background operation.
*/
openDownloadsListOnStart: true,
/**
* This represents the MIME type of the download.
*/
contentType: null,
/**
* This indicates the path of the application to be used to launch the file,
* or null if the file should be launched with the default application.
*/
launcherPath: null,
/**
* This contains application id to be used to launch the file,
* or null if the file is not meant to be launched with GIOHandlerApp.
*/
launcherId: null,
/**
* Raises the onchange notification.
*/
_notifyChange: function D_notifyChange() {
try {
if (this.onchange) {
this.onchange();
}
} catch (ex) {
console.error(ex);
}
},
/**
* The download may be stopped and restarted multiple times before it
* completes successfully. This may happen if any of the download attempts is
* canceled or fails.
*
* This property contains a promise that is linked to the current attempt, or
* null if the download is either stopped or in the process of being canceled.
* If the download restarts, this property is replaced with a new promise.
*
* The promise is resolved if the attempt it represents finishes successfully,
* and rejected if the attempt fails.
*/
_currentAttempt: null,
/**
* The download was launched to open from the Downloads Panel.
*/
_launchedFromPanel: false,
/**
* Starts the download for the first time, or restarts a download that failed
* or has been canceled.
*
* Calling this method when the download has been completed successfully has
* no effect, and the method returns a resolved promise. If the download is
* in progress, the method returns the same promise as the previous call.
*
* If the "cancel" method was called but the cancellation process has not
* finished yet, this method waits for the cancellation to finish, then
* restarts the download immediately.
*
* @note If you need to start a new download from the same source, rather than
* restarting a failed or canceled one, you should create a separate
* Download object with the same source as the current one.
*
* @return {Promise}
* @resolves When the download has finished successfully.
* @rejects JavaScript exception if the download failed.
*/
start: function D_start() {
// If the download succeeded, it's the final state, we have nothing to do.
if (this.succeeded) {
return Promise.resolve();
}
// If the download already started and hasn't failed or hasn't been
// canceled, return the same promise as the previous call, allowing the
// caller to wait for the current attempt to finish.
if (this._currentAttempt) {
return this._currentAttempt;
}
// While shutting down or disposing of this object, we prevent the download
// from returning to be in progress.
if (this._finalized) {
return Promise.reject(
new DownloadError({
message: "Cannot start after finalization.",
})
);
}
if (this.error && this.error.becauseBlockedByReputationCheck) {
return Promise.reject(
new DownloadError({
message: "Cannot start after being blocked by a reputation check.",
})
);
}
// Initialize all the status properties for a new or restarted download.
this.stopped = false;
this.canceled = false;
this.error = null;
// Avoid serializing the previous error, or it would be restored on the next
// startup, even if the download was restarted.
delete this._unknownProperties?.errorObj;
this.hasProgress = false;
this.hasBlockedData = false;
this.progress = 0;
this.totalBytes = 0;
this.currentBytes = 0;
this.startTime = new Date();
// Create a new deferred object and an associated promise before starting
// the actual download. We store it on the download as the current attempt.
let deferAttempt = Promise.withResolvers();
let currentAttempt = deferAttempt.promise;
this._currentAttempt = currentAttempt;
// Restart the progress and speed calculations from scratch.
this._lastProgressTimeMs = 0;
// This function propagates progress from the DownloadSaver object, unless
// it comes in late from a download attempt that was replaced by a new one.
// If the cancellation process for the download has started, then the update
// is ignored.
function DS_setProgressBytes(aCurrentBytes, aTotalBytes, aHasPartialData) {
if (this._currentAttempt == currentAttempt) {
this._setBytes(aCurrentBytes, aTotalBytes, aHasPartialData);
}
}
// This function propagates download properties from the DownloadSaver
// object, unless it comes in late from a download attempt that was
// replaced by a new one. If the cancellation process for the download has
// started, then the update is ignored.
function DS_setProperties(aOptions) {
if (this._currentAttempt != currentAttempt) {
return;
}
let changeMade = false;
for (let property of [
"contentType",
"progress",
"hasPartialData",
"hasBlockedData",
]) {
if (property in aOptions && this[property] != aOptions[property]) {
this[property] = aOptions[property];
changeMade = true;
}
}
if (changeMade) {
this._notifyChange();
}
}
// Now that we stored the promise in the download object, we can start the
// task that will actually execute the download.
deferAttempt.resolve(
(async () => {
// Wait upon any pending operation before restarting.
if (this._promiseCanceled) {
await this._promiseCanceled;
}
if (this._promiseRemovePartialData) {
try {
await this._promiseRemovePartialData;
} catch (ex) {
// Ignore any errors, which are already reported by the original
// caller of the removePartialData method.
}
}
// In case the download was restarted while cancellation was in progress,
// but the previous attempt actually succeeded before cancellation could
// be processed, it is possible that the download has already finished.
if (this.succeeded) {
return;
}
try {
if (this.downloadingToSameFile()) {
throw new DownloadError({
message: "Can't overwrite the source file.",
becauseTargetFailed: true,
});
}
// Disallow download if parental controls service restricts it.
if (
await lazy.DownloadIntegration.shouldBlockForParentalControls(this)
) {
throw new DownloadError({ becauseBlockedByParentalControls: true });
}
// We should check if we have been canceled in the meantime, after all
// the previous asynchronous operations have been executed and just
// before we call the "execute" method of the saver.
if (this._promiseCanceled) {
// The exception will become a cancellation in the "catch" block.
throw new Error(undefined);
}
// Execute the actual download through the saver object.
this._saverExecuting = true;
try {
await this.saver.execute(
DS_setProgressBytes.bind(this),
DS_setProperties.bind(this)
);
} catch (ex) {
// Remove the target file placeholder and all partial data when
// needed, independently of which code path failed. In some cases, the
// component executing the download may have already removed the file.
if (!this.hasPartialData && !this.hasBlockedData) {
await this.saver.removeData(true);
}
throw ex;
}
// Now that the actual saving finished, read the actual file size on
// disk, that may be different from the amount of data transferred.
await this.target.refresh();
// Check for the last time if the download has been canceled. This must
// be done right before setting the "stopped" property of the download,
// without any asynchronous operations in the middle, so that another
// cancellation request cannot start in the meantime and stay unhandled.
if (this._promiseCanceled) {
// To keep the internal state of the Download object consistent, we
// just delete the target and effectively cancel the download. Since
// the DownloadSaver succeeded, we already renamed the ".part" file to
// the final name, and this results in all the data being deleted.
await this.saver.removeData(true);
// Cancellation exceptions will be changed in the catch block below.
throw new DownloadError();
}
// Update the status properties for a successful download.
this.progress = 100;
this.succeeded = true;
this.hasPartialData = false;
} catch (originalEx) {
// We may choose a different exception to propagate in the code below,
// or wrap the original one. We do this mutation in a different variable
// because of the "no-ex-assign" ESLint rule.
let ex = originalEx;
// Fail with a generic status code on cancellation, so that the caller
// is forced to actually check the status properties to see if the
// download was canceled or failed because of other reasons.
if (this._promiseCanceled) {
throw new DownloadError({ message: "Download canceled." });
}
// An HTTP 450 error code is used by Windows to indicate that a uri is
// blocked by parental controls. This will prevent the download from
// occuring, so an error needs to be raised. This is not performed
// during the parental controls check above as it requires the request
// to start.
if (this._blockedByParentalControls) {
ex = new DownloadError({ becauseBlockedByParentalControls: true });
}
// Update the download error, unless a new attempt already started. The
// change in the status property is notified in the finally block.
if (this._currentAttempt == currentAttempt || !this._currentAttempt) {
if (!(ex instanceof DownloadError)) {
let properties = { innerException: ex };
if (ex.message) {
properties.message = ex.message;
}
ex = new DownloadError(properties);
}
// Don't store an error if it's an abort caused by shutdown, so the
// download can be retried automatically at the next startup.
if (
originalEx.result != Cr.NS_ERROR_ABORT ||
!Services.startup.isInOrBeyondShutdownPhase(
Ci.nsIAppStartup.SHUTDOWN_PHASE_APPSHUTDOWNCONFIRMED
)
) {
this.error = ex;
}
}
throw ex;
} finally {
// Any cancellation request has now been processed.
this._saverExecuting = false;
this._promiseCanceled = null;
// Update the status properties, unless a new attempt already started.
if (this._currentAttempt == currentAttempt || !this._currentAttempt) {
this._currentAttempt = null;
this.stopped = true;
this.speed = 0;
this._notifyChange();
if (this.succeeded) {
await this._succeed();
}
}
}
})()
);
// Notify the new download state before returning.
this._notifyChange();
return currentAttempt;
},
/**
* Perform the actions necessary when a Download succeeds.
*
* @return {Promise}
* @resolves When the steps to take after success have completed.
* @rejects JavaScript exception if any of the operations failed.
*/
async _succeed() {
await lazy.DownloadIntegration.downloadDone(this);
this._deferSucceeded.resolve();
if (this.launchWhenSucceeded) {
this.launch().catch(console.error);
// Always schedule files to be deleted at the end of the private browsing
// mode, regardless of the value of the pref.
if (this.source.isPrivate) {
lazy.gExternalAppLauncher.deleteTemporaryPrivateFileWhenPossible(
new lazy.FileUtils.File(this.target.path)
);
} else if (
Services.prefs.getBoolPref("browser.helperApps.deleteTempFileOnExit") &&
Services.prefs.getBoolPref(
"browser.download.start_downloads_in_tmp_dir",
false
)
) {
lazy.gExternalAppLauncher.deleteTemporaryFileOnExit(
new lazy.FileUtils.File(this.target.path)
);
}
}
},
/**
* When a request to unblock the download is received, contains a promise
* that will be resolved when the unblock request is completed. This property
* will then continue to hold the promise indefinitely.
*/
_promiseUnblock: null,
/**
* When a request to confirm the block of the download is received, contains
* a promise that will be resolved when cleaning up the download has
* completed. This property will then continue to hold the promise
* indefinitely.
*/
_promiseConfirmBlock: null,
/**
* Unblocks a download which had been blocked by reputation.
*
* The file will be moved out of quarantine and the download will be
* marked as succeeded.
*
* @return {Promise}
* @resolves When the Download has been unblocked and succeeded.
* @rejects JavaScript exception if any of the operations failed.
*/
unblock() {
if (this._promiseUnblock) {
return this._promiseUnblock;
}
if (this._promiseConfirmBlock) {
return Promise.reject(
new Error("Download block has been confirmed, cannot unblock.")
);
}
if (this.error?.becauseBlockedByReputationCheck) {
Glean.downloads.userActionOnBlockedDownload[
this.error.reputationCheckVerdict
].accumulateSingleSample(2); // unblock
}
if (
this.error?.reputationCheckVerdict == DownloadError.BLOCK_VERDICT_INSECURE
) {
// In this Error case, the download was actually canceled before it was
// passed to the Download UI. So we need to start the download here.
this.error = null;
this.succeeded = false;
this.hasBlockedData = false;
// This ensures the verdict will not get set again after the browser
// restarts and the download gets serialized and de-serialized again.
delete this._unknownProperties?.errorObj;
this.start()
.catch(err => {
if (err.becauseTargetFailed) {
// In case we cannot write to the target file
// retry with a new unique name
let uniquePath = lazy.DownloadPaths.createNiceUniqueFile(
new lazy.FileUtils.File(this.target.path)
).path;
this.target.path = uniquePath;
return this.start();
}
return Promise.reject(err);
})
.catch(err => {
if (!this.canceled) {
console.error(err);
}
this._notifyChange();
});
this._notifyChange();
this._promiseUnblock = lazy.DownloadIntegration.downloadDone(this);
return this._promiseUnblock;
}
if (!this.hasBlockedData) {
return Promise.reject(
new Error("unblock may only be called on Downloads with blocked data.")
);
}
this._promiseUnblock = (async () => {
try {
await IOUtils.move(this.target.partFilePath, this.target.path);
await this.target.refresh();
} catch (ex) {
await this.refresh();
this._promiseUnblock = null;
throw ex;
}
this.succeeded = true;
this.hasBlockedData = false;
this._notifyChange();
await this._succeed();
})();
return this._promiseUnblock;
},
/**
* Confirms that a blocked download should be cleaned up.
*
* If a download was blocked but retained on disk this method can be used
* to remove the file.
*
* @return {Promise}
* @resolves When the Download's data has been removed.
* @rejects JavaScript exception if any of the operations failed.
*/
confirmBlock() {
if (this._promiseConfirmBlock) {
return this._promiseConfirmBlock;
}
if (this._promiseUnblock) {
return Promise.reject(
new Error("Download is being unblocked, cannot confirmBlock.")
);
}
if (this.error?.becauseBlockedByReputationCheck) {
// We have to record the telemetry in both DownloadsCommon.deleteDownload
// and confirmBlock here. The former is for cases where users click
// "Remove file" in the download panel and the latter is when
// users click "X" button in about:downloads.
Glean.downloads.userActionOnBlockedDownload[
this.error.reputationCheckVerdict
].accumulateSingleSample(1); // confirm block
}
if (!this.hasBlockedData) {
return Promise.reject(
new Error(
"confirmBlock may only be called on Downloads with blocked data."
)
);
}
this._promiseConfirmBlock = (async () => {
// This call never throws exceptions. If the removal fails, the blocked
// data remains stored on disk in the ".part" file.
await this.saver.removeData();
this.hasBlockedData = false;
this._notifyChange();
})();
return this._promiseConfirmBlock;
},
/*
* Launches the file after download has completed. This can open
* the file with the default application for the target MIME type
* or file extension, or with a custom application if launcherPath
* or launcherId is set.
*
* @param options.openWhere Optional string indicating how to open when handling
* download by opening the target file URI.
* One of "window", "tab", "tabshifted"
* @param options.useSystemDefault
* Optional value indicating how to handle launching this download,
* this time only. Will override the associated mimeInfo.preferredAction
* @return {Promise}
* @resolves When the instruction to launch the file has been
* successfully given to the operating system. Note that
* the OS might still take a while until the file is actually
* launched.
* @rejects JavaScript exception if there was an error trying to launch
* the file.
*/
launch(options = {}) {
if (!this.succeeded) {
return Promise.reject(
new Error("launch can only be called if the download succeeded")
);
}
if (this._launchedFromPanel) {
Glean.downloads.fileOpened.add(1);
}
return lazy.DownloadIntegration.launchDownload(this, options);
},
/*
* Shows the folder containing the target file, or where the target file
* will be saved. This may be called at any time, even if the download
* failed or is currently in progress.
*
* @return {Promise}
* @resolves When the instruction to open the containing folder has been
* successfully given to the operating system. Note that
* the OS might still take a while until the folder is actually
* opened.
* @rejects JavaScript exception if there was an error trying to open
* the containing folder.
*/
showContainingDirectory: function D_showContainingDirectory() {
return lazy.DownloadIntegration.showContainingDirectory(this.target.path);
},
/**
* When a request to cancel the download is received, contains a promise that
* will be resolved when the cancellation request is processed. When the
* request is processed, this property becomes null again.
*/
_promiseCanceled: null,
/**
* True between the call to the "execute" method of the saver and the
* completion of the current download attempt.
*/
_saverExecuting: false,
/**
* Cancels the download.
*
* The cancellation request is asynchronous. Until the cancellation process
* finishes, temporary files or part files may still exist even if they are
* expected to be deleted.
*
* In case the download completes successfully before the cancellation request
* could be processed, this method has no effect, and it returns a resolved
* promise. You should check the properties of the download at the time the
* returned promise is resolved to determine if the download was cancelled.
*
* Calling this method when the download has been completed successfully,
* failed, or has been canceled has no effect, and the method returns a
* resolved promise. This behavior is designed for the case where the call
* to "cancel" happens asynchronously, and is consistent with the case where
* the cancellation request could not be processed in time.
*
* @return {Promise}
* @resolves When the cancellation process has finished.
* @rejects Never.
*/
cancel: function D_cancel() {
// If the download is currently stopped, we have nothing to do.
if (this.stopped) {
return Promise.resolve();
}
if (!this._promiseCanceled) {
// Start a new cancellation request.
this._promiseCanceled = new Promise(resolve => {
this._currentAttempt.then(resolve, resolve);
});
// The download can already be restarted.
this._currentAttempt = null;
// Notify that the cancellation request was received.
this.canceled = true;
this._notifyChange();
// Execute the actual cancellation through the saver object, in case it
// has already started. Otherwise, the cancellation will be handled just
// before the saver is started.
if (this._saverExecuting) {
this.saver.cancel();
}
}
return this._promiseCanceled;
},
/**
* Indicates whether any partially downloaded data should be retained, to use
* when restarting a failed or canceled download. The default is false.
*
* Whether partial data can actually be retained depends on the saver and the
* download source, and may not be known before the download is started.
*
* To have any effect, this property must be set before starting the download.
* Resetting this property to false after the download has already started
* will not remove any partial data.
*
* If this property is set to true, care should be taken that partial data is
* removed before the reference to the download is discarded. This can be
* done using the removePartialData or the "finalize" methods.
*/
tryToKeepPartialData: false,
/**
* When a request to remove partially downloaded data is received, contains a
* promise that will be resolved when the removal request is processed. When
* the request is processed, this property becomes null again.
*/
_promiseRemovePartialData: null,
/**
* Removes any partial data kept as part of a canceled or failed download.
*
* If the download is not canceled or failed, this method has no effect, and
* it returns a resolved promise. If the "cancel" method was called but the
* cancellation process has not finished yet, this method waits for the
* cancellation to finish, then removes the partial data.
*
* After this method has been called, if the tryToKeepPartialData property is
* still true when the download is restarted, partial data will be retained
* during the new download attempt.
*
* @return {Promise}
* @resolves When the partial data has been successfully removed.
* @rejects JavaScript exception if the operation could not be completed.
*/
removePartialData() {
if (!this.canceled && !this.error) {
return Promise.resolve();
}
if (!this._promiseRemovePartialData) {
this._promiseRemovePartialData = (async () => {
try {
// Wait upon any pending cancellation request.
if (this._promiseCanceled) {
await this._promiseCanceled;
}
// Ask the saver object to remove any partial data.
await this.saver.removeData();
// For completeness, clear the number of bytes transferred.
if (this.currentBytes != 0 || this.hasPartialData) {
this.currentBytes = 0;
this.hasPartialData = false;
this.target.refreshPartFileState();
this._notifyChange();
}
} finally {
this._promiseRemovePartialData = null;
}
})();
}
return this._promiseRemovePartialData;
},
/**
* Returns true if the download source is the same as the target file.
*/
downloadingToSameFile() {
if (!this.source.url || !this.source.url.startsWith("file:")) {
return false;
}
try {
let sourceUri = lazy.NetUtil.newURI(this.source.url);
let targetUri = lazy.NetUtil.newURI(
new lazy.FileUtils.File(this.target.path)
);
return sourceUri.equals(targetUri);
} catch (ex) {
return false;
}
},
/**
* This deferred object contains a promise that is resolved as soon as this
* download finishes successfully, and is never rejected. This property is
* initialized when the download is created, and never changes.
*/
_deferSucceeded: null,
/**
* Returns a promise that is resolved as soon as this download finishes
* successfully, even if the download was stopped and restarted meanwhile.
*
* You can use this property for scheduling download completion actions in the
* current session, for downloads that are controlled interactively. If the
* download is not controlled interactively, you should use the promise
* returned by the "start" method instead, to check for success or failure.
*
* @return {Promise}
* @resolves When the download has finished successfully.
* @rejects Never.
*/
whenSucceeded: function D_whenSucceeded() {
return this._deferSucceeded.promise;
},
/**
* Updates the state of a finished, failed, or canceled download based on the
* current state in the file system. If the download is in progress or it has
* been finalized, this method has no effect, and it returns a resolved
* promise.
*
* This allows the properties of the download to be updated in case the user
* moved or deleted the target file or its associated ".part" file.
*
* @return {Promise}
* @resolves When the operation has completed.
* @rejects Never.
*/
refresh() {
return (async () => {
if (!this.stopped || this._finalized) {
return;
}
if (this.succeeded) {
let oldExists = this.target.exists;
let oldSize = this.target.size;
await this.target.refresh();
if (oldExists != this.target.exists || oldSize != this.target.size) {
this._notifyChange();
}
return;
}
// Update the current progress from disk if we retained partial data.
if (
(this.hasPartialData || this.hasBlockedData) &&
this.target.partFilePath
) {
try {
let stat = await IOUtils.stat(this.target.partFilePath);
// Ignore the result if the state has changed meanwhile.
if (!this.stopped || this._finalized) {
return;
}
// Update the bytes transferred and the related progress properties.
this.currentBytes = stat.size;
if (this.totalBytes > 0) {
this.hasProgress = true;
this.progress = Math.floor(
(this.currentBytes / this.totalBytes) * 100
);
}
} catch (ex) {
if (ex.name != "NotFoundError") {
throw ex;
}
// Ignore the result if the state has changed meanwhile.
if (!this.stopped || this._finalized) {
return;
}
// In case we've blocked the Download becasue its
// insecure, we should not set hasBlockedData to
// false as its required to show the Unblock option.
if (
this.error.reputationCheckVerdict ==
DownloadError.BLOCK_VERDICT_INSECURE
) {
return;
}
this.hasBlockedData = false;
this.hasPartialData = false;
}
this._notifyChange();
}
})().catch(console.error);
},
/**
* True if the "finalize" method has been called. This prevents the download
* from starting again after having been stopped.
*/
_finalized: false,
/**
* True if the "finalize" has been called and fully finished it's execution.
*/
_finalizeExecuted: false,
/**
* Ensures that the download is stopped, and optionally removes any partial
* data kept as part of a canceled or failed download. After this method has
* been called, the download cannot be started again.
*
* This method should be used in place of "cancel" and removePartialData while
* shutting down or disposing of the download object, to prevent other callers
* from interfering with the operation. This is required because cancellation
* and other operations are asynchronous.
*
* @param aRemovePartialData
* Whether any partially downloaded data should be removed after the
* download has been stopped.
*
* @return {Promise}
* @resolves When the operation has finished successfully.
* @rejects JavaScript exception if an error occurred while removing the
* partially downloaded data.
*/
finalize(aRemovePartialData) {
// Prevents the download from starting again after having been stopped.
this._finalized = true;
let promise;
if (aRemovePartialData) {
// Cancel the download, in case it is currently in progress, then remove
// any partially downloaded data. The removal operation waits for
// cancellation to be completed before resolving the promise it returns.
this.cancel();
promise = this.removePartialData();
} else {
// Just cancel the download, in case it is currently in progress.
promise = this.cancel();
}
promise.then(() => {
// At this point, either removing data / just cancelling the download should be done.
this._finalizeExecuted = true;
});
return promise;
},
/**
* Deletes all file data associated with a download, preserving the download
* object itself and updating it for download views.
*/
async manuallyRemoveData() {
let { path } = this.target;
if (this.succeeded) {
// Temp files are made "read-only" by DownloadIntegration.downloadDone, so
// reset the permission bits to read/write. This won't be necessary after
// bug 1733587 since Downloads won't ever be temporary.
await IOUtils.setPermissions(path, 0o660);
await IOUtils.remove(path, { ignoreAbsent: true });
}
this.deleted = true;
await this.cancel();
await this.removePartialData();
// We need to guarantee that the UI is refreshed irrespective of what state
// the download is in when this is called, to ensure the download doesn't
// wind up stuck displaying as if it exists when it actually doesn't. And
// that means updating this.target.partFileExists no matter what.
await this.target.refreshPartFileState();
await this.refresh();
// The above methods will sometimes call _notifyChange, but not always. It
// depends on whether the download is `succeeded`, `stopped`, `canceled`,
// etc. Since this method needs to update the UI and can be invoked on any
// download as long as its target has some file on the system, we need to
// call _notifyChange no matter what state the download is in.
this._notifyChange();
},
/**
* Indicates the time of the last progress notification, expressed as the
* number of milliseconds since January 1, 1970, 00:00:00 UTC. This is zero
* until some bytes have actually been transferred.
*/
_lastProgressTimeMs: 0,
/**
* Updates progress notifications based on the number of bytes transferred.
*
* The number of bytes transferred is not updated unless enough time passed
* since this function was last called. This limits the computation load, in
* particular when the listeners update the user interface in response.
*
* @param aCurrentBytes
* Number of bytes transferred until now.
* @param aTotalBytes
* Total number of bytes to be transferred, or -1 if unknown.
* @param [aHasPartialData]
* Indicates whether the partially downloaded data can be used when
* restarting the download if it fails or is canceled.
*/
_setBytes: function D_setBytes(
aCurrentBytes,
aTotalBytes,
aHasPartialData = false
) {
let changeMade = this.hasPartialData != aHasPartialData;
this.hasPartialData = aHasPartialData;
// Unless aTotalBytes is -1, we can report partial download progress. In
// this case, notify when the related properties changed since last time.
if (
aTotalBytes != -1 &&
(!this.hasProgress || this.totalBytes != aTotalBytes)
) {
this.hasProgress = true;
this.totalBytes = aTotalBytes;
changeMade = true;
}
// Updating the progress and computing the speed require that enough time
// passed since the last update, or that we haven't started throttling yet.
let currentTimeMs = Date.now();
let intervalMs = currentTimeMs - this._lastProgressTimeMs;
if (intervalMs >= kProgressUpdateIntervalMs) {
// Don't compute the speed unless we started throttling notifications.
if (this._lastProgressTimeMs != 0) {
// Calculate the speed in bytes per second.
let rawSpeed =
((aCurrentBytes - this.currentBytes) / intervalMs) * 1000;
if (this.speed == 0) {
// When the previous speed is exactly zero instead of a fractional
// number, this can be considered the first element of the series.
this.speed = rawSpeed;
} else {
// Apply exponential smoothing, with a smoothing factor of 0.1.
this.speed = rawSpeed * 0.1 + this.speed * 0.9;
}
}
// Start throttling notifications only when we have actually received some
// bytes for the first time. The timing of the first part of the download
// is not reliable, due to possible latency in the initial notifications.
// This also allows automated tests to receive and verify the number of
// bytes initially transferred.
if (aCurrentBytes > 0) {
this._lastProgressTimeMs = currentTimeMs;
// Update the progress now that we don't need its previous value.
this.currentBytes = aCurrentBytes;
if (this.totalBytes > 0) {
this.progress = Math.floor(
(this.currentBytes / this.totalBytes) * 100
);
}
changeMade = true;
}
if (this.hasProgress && this.target && !this.target.partFileExists) {
this.target.refreshPartFileState();
}
}
if (changeMade) {
this._notifyChange();
}
},
/**
* Returns a static representation of the current object state.
*
* @return A JavaScript object that can be serialized to JSON.
*/
toSerializable() {
let serializable = {
source: this.source.toSerializable(),
target: this.target.toSerializable(),
};
let saver = this.saver.toSerializable();
if (!serializable.source || !saver) {
// If we are unable to serialize either the source or the saver,
// we won't persist the download.
return null;
}
// Simplify the representation for the most common saver type. If the saver
// is an object instead of a simple string, we can't simplify it because we
// need to persist all its properties, not only "type". This may happen for
// savers of type "copy" as well as other types.
if (saver !== "copy") {
serializable.saver = saver;
}
if (this.error) {
serializable.errorObj = this.error.toSerializable();
}
if (this.startTime) {
serializable.startTime = this.startTime.toJSON();
}
// These are serialized unless they are false, null, or empty strings.
for (let property of kPlainSerializableDownloadProperties) {
if (this[property]) {
serializable[property] = this[property];
}
}
serializeUnknownProperties(this, serializable);
return serializable;
},
/**
* Returns a value that changes only when one of the properties of a Download
* object that should be saved into a file also change. This excludes
* properties whose value doesn't usually change during the download lifetime.
*
* This function is used to determine whether the download should be
* serialized after a property change notification has been received.
*
* @return String representing the relevant download state.
*/
getSerializationHash() {
// The "succeeded", "canceled", "error", and startTime properties are not
// taken into account because they all change before the "stopped" property
// changes, and are not altered in other cases.
return (
this.stopped +
"," +
this.totalBytes +
"," +
this.hasPartialData +
"," +
this.contentType
);
},
};
/**
* Defines which properties of the Download object are serializable.
*/
const kPlainSerializableDownloadProperties = [
"succeeded",
"canceled",
"totalBytes",
"hasPartialData",
"hasBlockedData",
"tryToKeepPartialData",
"launcherPath",
"launcherId",
"launchWhenSucceeded",
"contentType",
"handleInternally",
"openDownloadsListOnStart",
];
/**
* Creates a new Download object from a serializable representation. This
* function is used by the createDownload method of Downloads.sys.mjs when a new
* Download object is requested, thus some properties may refer to live objects
* in place of their serializable representations.
*
* @param aSerializable
* An object with the following fields:
* {
* source: DownloadSource object, or its serializable representation.
* See DownloadSource.fromSerializable for details.
* target: DownloadTarget object, or its serializable representation.
* See DownloadTarget.fromSerializable for details.
* saver: Serializable representation of a DownloadSaver object. See
* DownloadSaver.fromSerializable for details. If omitted,
* defaults to "copy".
* }
*
* @return The newly created Download object.
*/
Download.fromSerializable = function (aSerializable) {
let download = new Download();
if (aSerializable.source instanceof DownloadSource) {
download.source = aSerializable.source;
} else {
download.source = DownloadSource.fromSerializable(aSerializable.source);
}
if (aSerializable.target instanceof DownloadTarget) {
download.target = aSerializable.target;
} else {
download.target = DownloadTarget.fromSerializable(aSerializable.target);
}
if ("saver" in aSerializable) {
download.saver = DownloadSaver.fromSerializable(aSerializable.saver);
} else {
download.saver = DownloadSaver.fromSerializable("copy");
}
download.saver.download = download;
if ("startTime" in aSerializable) {
let time = aSerializable.startTime.getTime
? aSerializable.startTime.getTime()
: aSerializable.startTime;
download.startTime = new Date(time);
}
// If 'errorObj' is present it will take precedence over the 'error' property.
// 'error' is a legacy property only containing message, which is insufficient
// to represent all of the error information.
//
// Instead of just replacing 'error' we use a new 'errorObj' so that previous
// versions will keep it as an unknown property.
if ("errorObj" in aSerializable) {
download.error = DownloadError.fromSerializable(aSerializable.errorObj);
} else if ("error" in aSerializable) {
download.error = aSerializable.error;
}
for (let property of kPlainSerializableDownloadProperties) {
if (property in aSerializable) {
download[property] = aSerializable[property];
}
}
deserializeUnknownProperties(
download,
aSerializable,
property =>
!kPlainSerializableDownloadProperties.includes(property) &&
property != "startTime" &&
property != "source" &&
property != "target" &&
property != "error" &&
property != "saver"
);
return download;
};
/**
* Represents the source of a download, for example a document or an URI.
*/
export var DownloadSource = function () {};
DownloadSource.prototype = {
/**
* String containing the URI for the download source.
*/
url: null,
/**
* String containing the original URL for the download source.
*/
originalUrl: null,
/**
* Indicates whether the download originated from a private window. This
* determines the context of the network request that is made to retrieve the
* resource.
*/
isPrivate: false,
/**
* Represents the referrerInfo of the download source, could be null for
* example if the download source is not HTTP.
*/
referrerInfo: null,
/**
* For downloads handled by the (default) DownloadCopySaver, this function
* can adjust the network channel before it is opened, for example to change
* the HTTP headers or to upload a stream as POST data.
*
* @note If this is defined this object will not be serializable, thus the
* Download object will not be persisted across sessions.
*
* @param aChannel
* The nsIChannel to be adjusted.
*
* @return {Promise}
* @resolves When the channel has been adjusted and can be opened.
* @rejects JavaScript exception that will cause the download to fail.
*/
adjustChannel: null,
/**
* For downloads handled by the (default) DownloadCopySaver, this function
* will determine, if provided, if a download can progress or has to be
* cancelled based on the HTTP status code of the network channel.
*
* @note If this is defined this object will not be serializable, thus the
* Download object will not be persisted across sessions.
*
* @param aDownload
* The download asking.
* @param aStatus
* The HTTP status in question
*
* @return {Boolean} Download can progress
*/
allowHttpStatus: null,
/**
* Represents the loadingPrincipal of the download source,
* could be null, in which case the system principal is used instead.
*/
loadingPrincipal: null,
/**
* Represents the cookieJarSettings of the download source, could be null if
* the download source is not from a document.
*/
cookieJarSettings: null,
/**
* Represents the authentication header of the download source, could be null if
* the download source had no authentication header.
*/
authHeader: null,
/**
* Returns a static representation of the current object state.
*
* @return A JavaScript object that can be serialized to JSON.
*/
toSerializable() {
if (this.adjustChannel) {
// If the callback was used, we can't reproduce this across sessions.
return null;
}
if (this.allowHttpStatus) {
// If the callback was used, we can't reproduce this across sessions.
return null;
}
let serializable = { url: this.url };
if (this.isPrivate) {
serializable.isPrivate = true;
}
if (this.referrerInfo && isString(this.referrerInfo)) {
serializable.referrerInfo = this.referrerInfo;
} else if (this.referrerInfo) {
serializable.referrerInfo = lazy.E10SUtils.serializeReferrerInfo(
this.referrerInfo
);
}
if (this.loadingPrincipal) {
serializable.loadingPrincipal = isString(this.loadingPrincipal)
? this.loadingPrincipal
: lazy.E10SUtils.serializePrincipal(this.loadingPrincipal);
}
if (this.cookieJarSettings) {
serializable.cookieJarSettings = isString(this.cookieJarSettings)
? this.cookieJarSettings
: lazy.E10SUtils.serializeCookieJarSettings(this.cookieJarSettings);
}
serializeUnknownProperties(this, serializable);
// Simplify the representation if we don't have other details.
if (Object.keys(serializable).length === 1) {
// serializable's only key is "url", just return the URL as a string.
return this.url;
}
return serializable;
},
};
/**
* Creates a new DownloadSource object from its serializable representation.
*
* @param aSerializable
* Serializable representation of a DownloadSource object. This may be a
* string containing the URI for the download source, an nsIURI, or an
* object with the following properties:
* {
* url: String containing the URI for the download source.
* isPrivate: Indicates whether the download originated from a private
* window. If omitted, the download is public.
* referrerInfo: represents the referrerInfo of the download source.
* Can be omitted or null for example if the download
* source is not HTTP.
* cookieJarSettings: represents the cookieJarSettings of the download
* source. Can be omitted or null if the download
* source is not from a document.
* adjustChannel: For downloads handled by (default) DownloadCopySaver,
* this function can adjust the network channel before
* it is opened, for example to change the HTTP headers
* or to upload a stream as POST data. Optional.
* allowHttpStatus: For downloads handled by the (default)
* DownloadCopySaver, this function will determine, if
* provided, if a download can progress or has to be
* cancelled based on the HTTP status code of the
* network channel.
* }
*
* @return The newly created DownloadSource object.
*/
DownloadSource.fromSerializable = function (aSerializable) {
let source = new DownloadSource();
if (isString(aSerializable)) {
// Convert String objects to primitive strings at this point.
source.url = aSerializable.toString();
} else if (aSerializable instanceof Ci.nsIURI) {
source.url = aSerializable.spec;
} else {
// Convert String objects to primitive strings at this point.
source.url = aSerializable.url.toString();
for (let propName of ["isPrivate", "userContextId", "browsingContextId"]) {
if (propName in aSerializable) {
source[propName] = aSerializable[propName];
}
}
if ("originalUrl" in aSerializable) {
source.originalUrl = aSerializable.originalUrl;
}
if ("referrerInfo" in aSerializable) {
// Quick pass, pass directly nsIReferrerInfo, we don't need to serialize
// and deserialize
if (aSerializable.referrerInfo instanceof Ci.nsIReferrerInfo) {
source.referrerInfo = aSerializable.referrerInfo;
} else {
source.referrerInfo = lazy.E10SUtils.deserializeReferrerInfo(
aSerializable.referrerInfo
);
}
}
if ("loadingPrincipal" in aSerializable) {
// Quick pass, pass directly nsIPrincipal, we don't need to serialize
// and deserialize
if (aSerializable.loadingPrincipal instanceof Ci.nsIPrincipal) {
source.loadingPrincipal = aSerializable.loadingPrincipal;
} else {
source.loadingPrincipal = lazy.E10SUtils.deserializePrincipal(
aSerializable.loadingPrincipal
);
}
}
if ("adjustChannel" in aSerializable) {
source.adjustChannel = aSerializable.adjustChannel;
}
if ("allowHttpStatus" in aSerializable) {
source.allowHttpStatus = aSerializable.allowHttpStatus;
}
if ("cookieJarSettings" in aSerializable) {
if (aSerializable.cookieJarSettings instanceof Ci.nsICookieJarSettings) {
source.cookieJarSettings = aSerializable.cookieJarSettings;
} else {
source.cookieJarSettings = lazy.E10SUtils.deserializeCookieJarSettings(
aSerializable.cookieJarSettings
);
}
}
if ("authHeader" in aSerializable) {
source.authHeader = aSerializable.authHeader;
}
deserializeUnknownProperties(
source,
aSerializable,
property =>
property != "url" &&
property != "originalUrl" &&
property != "isPrivate" &&
property != "referrerInfo" &&
property != "cookieJarSettings" &&
property != "authHeader"
);
}
return source;
};
/**
* Represents the target of a download, for example a file in the global
* downloads directory, or a file in the system temporary directory.
*/
export var DownloadTarget = function () {};
DownloadTarget.prototype = {
/**
* String containing the path of the target file.
*/
path: null,
/**
* String containing the path of the ".part" file containing the data
* downloaded so far, or null to disable the use of a ".part" file to keep
* partially downloaded data.
*/
partFilePath: null,
/**
* Indicates whether the target file exists.
*
* This is a dynamic property updated when the download finishes or when the
* "refresh" method of the Download object is called. It can be used by the
* front-end to reduce I/O compared to checking the target file directly.
*/
exists: false,
/**
* Indicates whether the part file exists. Like `exists`, this is updated
* dynamically to reduce I/O compared to checking the target file directly.
*/
partFileExists: false,
/**
* Size in bytes of the target file, or zero if the download has not finished.
*
* Even if the target file does not exist anymore, this property may still
* have a value taken from the download metadata. If the metadata has never
* been available in this session and the size cannot be obtained from the
* file because it has already been deleted, this property will be zero.
*
* For single-file downloads, this property will always match the actual file
* size on disk, while the totalBytes property of the Download object, when
* available, may represent the size of the encoded data instead.
*
* For downloads involving multiple files, like complete web pages saved to
* disk, the meaning of this value is undefined. It currently matches the size
* of the main file only rather than the sum of all the written data.
*
* This is a dynamic property updated when the download finishes or when the
* "refresh" method of the Download object is called. It can be used by the
* front-end to reduce I/O compared to checking the target file directly.
*/
size: 0,
/**
* Sets the "exists" and "size" properties based on the actual file on disk.
*
* @return {Promise}
* @resolves When the operation has finished successfully.
* @rejects JavaScript exception.
*/
async refresh() {
try {
this.size = (await IOUtils.stat(this.path)).size;
this.exists = true;
} catch (ex) {
// Report any error not caused by the file not being there. In any case,
// the size of the download is not updated and the known value is kept.
if (ex.name != "NotFoundError") {
console.error(ex);
}
this.exists = false;
}
this.refreshPartFileState();
},
async refreshPartFileState() {
if (!this.partFilePath) {
this.partFileExists = false;
return;
}
try {
this.partFileExists = (await IOUtils.stat(this.partFilePath)).size > 0;
} catch (ex) {
if (ex.name != "NotFoundError") {
console.error(ex);
}
this.partFileExists = false;
}
},
/**
* Returns a static representation of the current object state.
*
* @return A JavaScript object that can be serialized to JSON.
*/
toSerializable() {
// Simplify the representation if we don't have other details.
if (!this.partFilePath && !this._unknownProperties) {
return this.path;
}
let serializable = { path: this.path, partFilePath: this.partFilePath };
serializeUnknownProperties(this, serializable);
return serializable;
},
};
/**
* Creates a new DownloadTarget object from its serializable representation.
*
* @param aSerializable
* Serializable representation of a DownloadTarget object. This may be a
* string containing the path of the target file, an nsIFile, or an
* object with the following properties:
* {
* path: String containing the path of the target file.
* partFilePath: optional string containing the part file path.
* }
*
* @return The newly created DownloadTarget object.
*/
DownloadTarget.fromSerializable = function (aSerializable) {
let target = new DownloadTarget();
if (isString(aSerializable)) {
// Convert String objects to primitive strings at this point.
target.path = aSerializable.toString();
} else if (aSerializable instanceof Ci.nsIFile) {
// Read the "path" property of nsIFile after checking the object type.
target.path = aSerializable.path;
} else {
// Read the "path" property of the serializable DownloadTarget
// representation, converting String objects to primitive strings.
target.path = aSerializable.path.toString();
if ("partFilePath" in aSerializable) {
target.partFilePath = aSerializable.partFilePath;
}
deserializeUnknownProperties(
target,
aSerializable,
property => property != "path" && property != "partFilePath"
);
}
return target;
};
/**
* Provides detailed information about a download failure.
*
* @param aProperties
* Object which may contain any of the following properties:
* {
* result: Result error code, defaulting to Cr.NS_ERROR_FAILURE
* message: String error message to be displayed in the console, or
* null to use the message associated with the result code.
* inferCause: If true, attempts to determine if the cause of the
* download is a network failure or a local file failure,
* based on a set of known values of the result code.
* This is useful when the error is received by a
* component that handles both aspects of the download.
* localizedReason: If available, is a localized reason for the error
* that can be directly displayed in the UI.
* }
* The properties object may also contain any of the DownloadError's
* because properties, which will be set accordingly in the error object.
*/
export var DownloadError = function (aProperties) {
const NS_ERROR_MODULE_BASE_OFFSET = 0x45;
const NS_ERROR_MODULE_NETWORK = 6;
const NS_ERROR_MODULE_FILES = 13;
// Set the error name used by the Error object prototype first.
this.name = "DownloadError";
this.result = aProperties.result || Cr.NS_ERROR_FAILURE;
this.localizedReason = aProperties.localizedReason;
if (aProperties.message) {
--> --------------------
--> maximum size reached
--> --------------------
