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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#include "nsISupports.idl"
+
+interface nsIArray;
+interface nsIBackgroundFileSaverObserver;
+interface nsIFile;
+
+/**
+ * Allows saving data to a file, while handling all the input/output on a
+ * background thread, including the initial file name assignment and any
+ * subsequent renaming of the target file.
+ *
+ * This interface is designed for file downloads. Generally, they start in the
+ * temporary directory, while the user is selecting the final name. Then, they
+ * are moved to the chosen target directory with a ".part" extension appended to
+ * the file name. Finally, they are renamed when the download is completed.
+ *
+ * Components implementing both nsIBackgroundFileSaver and nsIStreamListener
+ * allow data to be fed using an implementation of OnDataAvailable that never
+ * blocks the calling thread. They suspend the request that drives the stream
+ * listener in case too much data is being fed, and resume it when the data has
+ * been written. Calling OnStopRequest does not necessarily close the target
+ * file, and the Finish method must be called to complete the operation.
+ *
+ * Components implementing both nsIBackgroundFileSaver and nsIAsyncOutputStream
+ * allow data to be fed directly to the non-blocking output stream, that however
+ * may return NS_BASE_STREAM_WOULD_BLOCK in case too much data is being fed.
+ * Closing the output stream does not necessarily close the target file, and the
+ * Finish method must be called to complete the operation.
+ *
+ * @remarks Implementations may require the consumer to always call Finish. If
+ * the object reference is released without calling Finish, a memory
+ * leak may occur, and the target file might be kept locked. All
+ * public methods of the interface may only be called from the main
+ * thread.
+ */
+[scriptable, uuid(c43544a4-682c-4262-b407-2453d26e660d)]
+interface nsIBackgroundFileSaver : nsISupports
+{
+ /**
+ * This observer receives notifications when the target file name changes and
+ * when the operation completes, successfully or not.
+ *
+ * @remarks A strong reference to the observer is held. Notification events
+ * are dispatched to the thread that created the object that
+ * implements nsIBackgroundFileSaver.
+ */
+ attribute nsIBackgroundFileSaverObserver observer;
+
+ /**
+ * An Array of Array of Array of bytes, representing a chain of
+ * X.509 certificates, the last of which signed the downloaded file.
+ * Each list may belong to a different signer and contain certificates
+ * all the way up to the root.
+ *
+ * @throws NS_ERROR_NOT_AVAILABLE
+ * In case this is called before the onSaveComplete method has been
+ * called to notify success, or enableSignatureInfo has not been
+ * called.
+ */
+ readonly attribute Array<Array<Array<uint8_t> > > signatureInfo;
+
+ /**
+ * The SHA-256 hash, in raw bytes, associated with the data that was saved.
+ *
+ * In case the enableAppend method has been called, the hash computation
+ * includes the contents of the existing file, if any.
+ *
+ * @throws NS_ERROR_NOT_AVAILABLE
+ * In case the enableSha256 method has not been called, or before the
+ * onSaveComplete method has been called to notify success.
+ */
+ readonly attribute ACString sha256Hash;
+
+ /**
+ * Instructs the component to compute the signatureInfo of the target file,
+ * and make it available in the signatureInfo property.
+ *
+ * @remarks This must be set on the main thread before the first call to
+ * setTarget.
+ */
+ void enableSignatureInfo();
+
+ /**
+ * Instructs the component to compute the SHA-256 hash of the target file, and
+ * make it available in the sha256Hash property.
+ *
+ * @remarks This must be set on the main thread before the first call to
+ * setTarget.
+ */
+ void enableSha256();
+
+ /**
+ * Instructs the component to append data to the initial target file, that
+ * will be specified by the first call to the setTarget method, instead of
+ * overwriting the file.
+ *
+ * If the initial target file does not exist, this method has no effect.
+ *
+ * @remarks This must be set on the main thread before the first call to
+ * setTarget.
+ */
+ void enableAppend();
+
+ /**
+ * Sets the name of the output file to be written. The target can be changed
+ * after data has already been fed, in which case the existing file will be
+ * moved to the new destination.
+ *
+ * In case the specified file already exists, and this method is called for
+ * the first time, the file may be either overwritten or appended to, based on
+ * whether the enableAppend method was called. Subsequent calls always
+ * overwrite the specified target file with the previously saved data.
+ *
+ * No file will be written until this function is called at least once. It's
+ * recommended not to feed any data until the output file is set.
+ *
+ * If an input/output error occurs with the specified file, the save operation
+ * fails. Failure is notified asynchronously through the observer.
+ *
+ * @param aTarget
+ * New output file to be written.
+ * @param aKeepPartial
+ * Indicates whether aFile should be kept as partially completed,
+ * rather than deleted, if the operation fails or is canceled. This is
+ * generally set for downloads that use temporary ".part" files.
+ */
+ void setTarget(in nsIFile aTarget, in bool aKeepPartial);
+
+ /**
+ * Terminates access to the output file, then notifies the observer with the
+ * specified status code. A failure code will force the operation to be
+ * canceled, in which case the output file will be deleted if requested.
+ *
+ * This forces the involved streams to be closed, thus no more data should be
+ * fed to the component after this method has been called.
+ *
+ * This is the last method that should be called on this object, and the
+ * target file name cannot be changed anymore after this method has been
+ * called. Conversely, before calling this method, the file can still be
+ * renamed even if all the data has been fed.
+ *
+ * @param aStatus
+ * Result code that determines whether the operation should succeed or
+ * be canceled, and is notified to the observer. If the operation
+ * fails meanwhile for other reasons, or the observer has been already
+ * notified of completion, this status code is ignored.
+ */
+ void finish(in nsresult aStatus);
+};
+
+[scriptable, uuid(ee7058c3-6e54-4411-b76b-3ce87b76fcb6)]
+interface nsIBackgroundFileSaverObserver : nsISupports
+{
+ /**
+ * Called when the name of the output file has been determined. This function
+ * may be called more than once if the target file is renamed while saving.
+ *
+ * @param aSaver
+ * Reference to the object that raised the notification.
+ * @param aTarget
+ * Name of the file that is being written.
+ */
+ void onTargetChange(in nsIBackgroundFileSaver aSaver, in nsIFile aTarget);
+
+ /**
+ * Called when the operation completed, and the target file has been closed.
+ * If the operation succeeded, the target file is ready to be used, otherwise
+ * it might have been already deleted.
+ *
+ * @param aSaver
+ * Reference to the object that raised the notification.
+ * @param aStatus
+ * Result code that determines whether the operation succeeded or
+ * failed, as well as the failure reason.
+ */
+ void onSaveComplete(in nsIBackgroundFileSaver aSaver, in nsresult aStatus);
+};