netwerk/base/nsIBackgroundFileSaver.idl

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsISupports.idl"
   8
   9 interface nsIArray;
  10 interface nsIBackgroundFileSaverObserver;
  11 interface nsIFile;
  12
  13 /**
  14  * Allows saving data to a file, while handling all the input/output on a
  15  * background thread, including the initial file name assignment and any
  16  * subsequent renaming of the target file.
  17  *
  18  * This interface is designed for file downloads.  Generally, they start in the
  19  * temporary directory, while the user is selecting the final name.  Then, they
  20  * are moved to the chosen target directory with a ".part" extension appended to
  21  * the file name.  Finally, they are renamed when the download is completed.
  22  *
  23  * Components implementing both nsIBackgroundFileSaver and nsIStreamListener
  24  * allow data to be fed using an implementation of OnDataAvailable that never
  25  * blocks the calling thread.  They suspend the request that drives the stream
  26  * listener in case too much data is being fed, and resume it when the data has
  27  * been written.  Calling OnStopRequest does not necessarily close the target
  28  * file, and the Finish method must be called to complete the operation.
  29  *
  30  * Components implementing both nsIBackgroundFileSaver and nsIAsyncOutputStream
  31  * allow data to be fed directly to the non-blocking output stream, that however
  32  * may return NS_BASE_STREAM_WOULD_BLOCK in case too much data is being fed.
  33  * Closing the output stream does not necessarily close the target file, and the
  34  * Finish method must be called to complete the operation.
  35  *
  36  * @remarks Implementations may require the consumer to always call Finish.  If
  37  *          the object reference is released without calling Finish, a memory
  38  *          leak may occur, and the target file might be kept locked. All
  39  *          public methods of the interface may only be called from the main
  40  *          thread.
  41  */
  42 [scriptable, uuid(c43544a4-682c-4262-b407-2453d26e660d)]
  43 interface nsIBackgroundFileSaver : nsISupports
  44 {
  45   /**
  46    * This observer receives notifications when the target file name changes and
  47    * when the operation completes, successfully or not.
  48    *
  49    * @remarks A strong reference to the observer is held.  Notification events
  50    *          are dispatched to the thread that created the object that
  51    *          implements nsIBackgroundFileSaver.
  52    */
  53   attribute nsIBackgroundFileSaverObserver observer;
  54
  55   /**
  56    * An nsIArray of nsIX509CertList, representing a chain of X.509 signatures on
  57    * the downloaded file. Each list may belong to a different signer and contain
  58    * certificates all the way up to the root.
  59    *
  60    * @throws NS_ERROR_NOT_AVAILABLE
  61    *         In case this is called before the onSaveComplete method has been
  62    *         called to notify success, or enableSignatureInfo has not been
  63    *         called.
  64    */
  65   readonly attribute nsIArray signatureInfo;
  66
  67   /**
  68    * The SHA-256 hash, in raw bytes, associated with the data that was saved.
  69    *
  70    * In case the enableAppend method has been called, the hash computation
  71    * includes the contents of the existing file, if any.
  72    *
  73    * @throws NS_ERROR_NOT_AVAILABLE
  74    *         In case the enableSha256 method has not been called, or before the
  75    *         onSaveComplete method has been called to notify success.
  76    */
  77   readonly attribute ACString sha256Hash;
  78
  79   /**
  80    * Instructs the component to compute the signatureInfo of the target file,
  81    * and make it available in the signatureInfo property.
  82    *
  83    * @remarks This must be set on the main thread before the first call to
  84    *          setTarget.
  85    */
  86   void enableSignatureInfo();
  87
  88   /**
  89    * Instructs the component to compute the SHA-256 hash of the target file, and
  90    * make it available in the sha256Hash property.
  91    *
  92    * @remarks This must be set on the main thread before the first call to
  93    *          setTarget.
  94    */
  95   void enableSha256();
  96
  97   /**
  98    * Instructs the component to append data to the initial target file, that
  99    * will be specified by the first call to the setTarget method, instead of
 100    * overwriting the file.
 101    *
 102    * If the initial target file does not exist, this method has no effect.
 103    *
 104    * @remarks This must be set on the main thread before the first call to
 105    *          setTarget.
 106    */
 107   void enableAppend();
 108
 109   /**
 110    * Sets the name of the output file to be written.  The target can be changed
 111    * after data has already been fed, in which case the existing file will be
 112    * moved to the new destination.
 113    *
 114    * In case the specified file already exists, and this method is called for
 115    * the first time, the file may be either overwritten or appended to, based on
 116    * whether the enableAppend method was called.  Subsequent calls always
 117    * overwrite the specified target file with the previously saved data.
 118    *
 119    * No file will be written until this function is called at least once.  It's
 120    * recommended not to feed any data until the output file is set.
 121    *
 122    * If an input/output error occurs with the specified file, the save operation
 123    * fails.  Failure is notified asynchronously through the observer.
 124    *
 125    * @param aTarget
 126    *        New output file to be written.
 127    * @param aKeepPartial
 128    *        Indicates whether aFile should be kept as partially completed,
 129    *        rather than deleted, if the operation fails or is canceled.  This is
 130    *        generally set for downloads that use temporary ".part" files.
 131    */
 132   void setTarget(in nsIFile aTarget, in bool aKeepPartial);
 133
 134   /**
 135    * Terminates access to the output file, then notifies the observer with the
 136    * specified status code.  A failure code will force the operation to be
 137    * canceled, in which case the output file will be deleted if requested.
 138    *
 139    * This forces the involved streams to be closed, thus no more data should be
 140    * fed to the component after this method has been called.
 141    *
 142    * This is the last method that should be called on this object, and the
 143    * target file name cannot be changed anymore after this method has been
 144    * called.  Conversely, before calling this method, the file can still be
 145    * renamed even if all the data has been fed.
 146    *
 147    * @param aStatus
 148    *        Result code that determines whether the operation should succeed or
 149    *        be canceled, and is notified to the observer.  If the operation
 150    *        fails meanwhile for other reasons, or the observer has been already
 151    *        notified of completion, this status code is ignored.
 152    */
 153   void finish(in nsresult aStatus);
 154 };
 155
 156 [scriptable, uuid(ee7058c3-6e54-4411-b76b-3ce87b76fcb6)]
 157 interface nsIBackgroundFileSaverObserver : nsISupports
 158 {
 159   /**
 160    * Called when the name of the output file has been determined.  This function
 161    * may be called more than once if the target file is renamed while saving.
 162    *
 163    * @param aSaver
 164    *        Reference to the object that raised the notification.
 165    * @param aTarget
 166    *        Name of the file that is being written.
 167    */
 168   void onTargetChange(in nsIBackgroundFileSaver aSaver, in nsIFile aTarget);
 169
 170   /**
 171    * Called when the operation completed, and the target file has been closed.
 172    * If the operation succeeded, the target file is ready to be used, otherwise
 173    * it might have been already deleted.
 174    *
 175    * @param aSaver
 176    *        Reference to the object that raised the notification.
 177    * @param aStatus
 178    *        Result code that determines whether the operation succeeded or
 179    *        failed, as well as the failure reason.
 180    */
 181   void onSaveComplete(in nsIBackgroundFileSaver aSaver, in nsresult aStatus);
 182 };