dom/filesystem/FileSystemTaskBase.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=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 file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_dom_FileSystemTaskBase_h
   8 #define mozilla_dom_FileSystemTaskBase_h
   9
  10 #include "mozilla/dom/FileSystemRequestParent.h"
  11 #include "mozilla/dom/PFileSystemRequestChild.h"
  12 #include "nsIGlobalObject.h"
  13 #include "nsThreadUtils.h"
  14
  15 namespace mozilla {
  16 class ErrorResult;
  17
  18 namespace dom {
  19
  20 class BlobImpl;
  21 class FileSystemBase;
  22 class FileSystemParams;
  23
  24 /*
  25  * The base class to implement a Task class.
  26  * The file system operations can only be performed in the parent process. In
  27  * order to avoid duplicated code, we used PBackground for child-parent and
  28  * parent-parent communications.
  29  *
  30  * The following diagram illustrates the how a API call from the content page
  31  * starts a task and gets call back results.
  32  *
  33  * The left block is the call sequence inside any process loading content, while
  34  * the right block is the call sequence only inside the parent process.
  35  *
  36  *       Page
  37  *        |
  38  *        | (1)
  39  *  ______|_________________________     |    _________________________________
  40  * |      |                          |   |   |                                 |
  41  * |      |                          |   |   |                                 |
  42  * |      V                          |  IPC  | PBackground thread on           |
  43  * | [new FileSystemTaskChildBase()] |   |   | the parent process              |
  44  * |         |                       |   |   |                                 |
  45  * |         | (2)                   |       |                                 |
  46  * |         V                       |  (3)  |                                 |
  47  * |    [GetRequestParams]------------------->[new FileSystemTaskParentBase()] |
  48  * |                                 |       |          |                      |
  49  * |                                 |   |   |          | (4)   _____________  |
  50  * |                                 |   |   |          |      |             | |
  51  * |                                 |   |   |          |      | I/O Thread  | |
  52  * |                                 |   |   |          |      |             | |
  53  * |                                 |   |   |          ---------> [IOWork]  | |
  54  * |                                 |  IPC  |                 |     |       | |
  55  * |                                 |   |   |                 |     | (5)   | |
  56  * |                                 |   |   |          --------------       | |
  57  * |                                 |   |   |          |      |_____________| |
  58  * |                                 |   |   |          |                      |
  59  * |                                 |   |   |          V                      |
  60  * |                                 |   |   |     [HandleResult]              |
  61  * |                                 |   |   |          |                      |
  62  * |                                 |       |          | (6)                  |
  63  * |                                 |  (7)  |          V                      |
  64  * |   [SetRequestResult]<---------------------[GetRequestResult]              |
  65  * |       |                         |       |                                 |
  66  * |       | (8)                     |   |   |                                 |
  67  * |       V                         |   |   |                                 |
  68  * |[HandlerCallback]                |  IPC  |                                 |
  69  * |_______|_________________________|   |   |_________________________________|
  70  *         |                             |
  71  *         V
  72  *        Page
  73  *
  74  * 1. From the process that is handling the request
  75  * Child/Parent (it can be in any process):
  76  *   (1) Call FileSystem API from content page with JS. Create a task and run.
  77  *   The base constructor [FileSystemTaskChildBase()] of the task should be
  78  *   called.
  79  *   (2) Forward the task to the parent process through the IPC and call
  80  *   [GetRequestParams] to prepare the parameters of the IPC.
  81  * Parent:
  82  *   (3) The parent process receives IPC and handle it in
  83  *   FileystemRequestParent. Get the IPC parameters and create a task to run the
  84  *   IPC task.
  85  *   (4) The task operation will be performed in the member function of
  86  * [IOWork]. A I/O  thread will be created to run that function. If error occurs
  87  *   during the operation, call [SetError] to record the error and then abort.
  88  *   (5) After finishing the task operation, call [HandleResult] to send the
  89  *   result back to the child process though the IPC.
  90  *   (6) Call [GetRequestResult] request result to prepare the parameters of the
  91  *   IPC. Because the formats of the error result for different task are the
  92  *   same, FileSystemTaskChildBase can handle the error message without
  93  *   interfering.
  94  *   Each task only needs to implement its specific success result preparation
  95  *   function -[GetSuccessRequestResult].
  96  * Child/Parent:
  97  *   (7) The process receives IPC and calls [SetRequestResult] to get the
  98  *   task result. Each task needs to implement its specific success result
  99  *   parsing function [SetSuccessRequestResult] to get the success result.
 100  *   (8) Call [HandlerCallback] to send the task result to the content page.
 101  */
 102 class FileSystemTaskChildBase : public PFileSystemRequestChild {
 103   friend class PFileSystemRequestChild;
 104
 105  public:
 106   NS_INLINE_DECL_REFCOUNTING(FileSystemTaskChildBase, final)
 107
 108   /*
 109    * Start the task. It will dispatch all the information to the parent process,
 110    * PBackground thread. This method must be called from the owning thread.
 111    */
 112   void Start();
 113
 114   /*
 115    * The error codes are defined in xpcom/base/ErrorList.h and their
 116    * corresponding error name and message are defined in dom/base/domerr.msg.
 117    */
 118   void SetError(const nsresult& aErrorCode);
 119
 120   FileSystemBase* GetFileSystem() const;
 121
 122   /*
 123    * After the task is completed, this function will be called to pass the task
 124    * result to the content page. This method is called in the owning thread.
 125    * Override this function to handle the call back to the content page.
 126    */
 127   virtual void HandlerCallback() = 0;
 128
 129   bool HasError() const { return NS_FAILED(mErrorValue); }
 130
 131  protected:
 132   /*
 133    * To create a task to handle the page content request.
 134    */
 135   FileSystemTaskChildBase(nsIGlobalObject* aGlobalObject,
 136                           FileSystemBase* aFileSystem);
 137
 138   virtual ~FileSystemTaskChildBase();
 139
 140   /*
 141    * Wrap the task parameter to FileSystemParams for sending it through IPC.
 142    * It will be called when we need to forward a task from the child process to
 143    * the parent process. This method runs in the owning thread.
 144    * @param filesystem The string representation of the file system.
 145    */
 146   virtual FileSystemParams GetRequestParams(const nsString& aSerializedDOMPath,
 147                                             ErrorResult& aRv) const = 0;
 148
 149   /*
 150    * Unwrap the IPC message to get the task success result.
 151    * It will be called when the task is completed successfully and an IPC
 152    * message is received in the child process and we want to get the task
 153    * success result. This method runs in the owning thread.
 154    */
 155   virtual void SetSuccessRequestResult(const FileSystemResponseValue& aValue,
 156                                        ErrorResult& aRv) = 0;
 157
 158   // Overrides PFileSystemRequestChild
 159   virtual mozilla::ipc::IPCResult Recv__delete__(
 160       const FileSystemResponseValue& value) final;
 161
 162   nsresult mErrorValue;
 163   RefPtr<FileSystemBase> mFileSystem;
 164   nsCOMPtr<nsIGlobalObject> mGlobalObject;
 165
 166  private:
 167   /*
 168    * Unwrap the IPC message to get the task result.
 169    * It will be called when the task is completed and an IPC message is received
 170    * in the content process and we want to get the task result. This runs on the
 171    * owning thread.
 172    */
 173   void SetRequestResult(const FileSystemResponseValue& aValue);
 174 };
 175
 176 // This class is the 'alter ego' of FileSystemTaskChildBase in the PBackground
 177 // world.
 178 class FileSystemTaskParentBase : public Runnable {
 179  public:
 180   FileSystemTaskParentBase()
 181       : Runnable("FileSystemTaskParentBase"),
 182         mErrorValue(NS_ERROR_NOT_INITIALIZED) {}
 183
 184   /*
 185    * Start the task. This must be called from the PBackground thread only.
 186    */
 187   void Start();
 188
 189   /*
 190    * The error codes are defined in xpcom/base/ErrorList.h and their
 191    * corresponding error name and message are defined in dom/base/domerr.msg.
 192    */
 193   void SetError(const nsresult& aErrorCode);
 194
 195   /*
 196    * The function to perform task operation. It will be run on the I/O
 197    * thread of the parent process.
 198    * Overrides this function to define the task operation for individual task.
 199    */
 200   virtual nsresult IOWork() = 0;
 201
 202   /*
 203    * Wrap the task success result to FileSystemResponseValue for sending it
 204    * through IPC. This method runs in the PBackground thread.
 205    * It will be called when the task is completed successfully and we need to
 206    * send the task success result back to the child process.
 207    */
 208   virtual FileSystemResponseValue GetSuccessRequestResult(
 209       ErrorResult& aRv) const = 0;
 210
 211   /*
 212    * After finishing the task operation, handle the task result.
 213    * If it is an IPC task, send back the IPC result. It runs on the PBackground
 214    * thread.
 215    */
 216   void HandleResult();
 217
 218   bool HasError() const { return NS_FAILED(mErrorValue); }
 219
 220   NS_IMETHOD
 221   Run() override;
 222
 223   virtual nsresult GetTargetPath(nsAString& aPath) const = 0;
 224
 225  private:
 226   /*
 227    * Wrap the task result to FileSystemResponseValue for sending it through IPC.
 228    * It will be called when the task is completed and we need to
 229    * send the task result back to the content. This runs on the PBackground
 230    * thread.
 231    */
 232   FileSystemResponseValue GetRequestResult() const;
 233
 234  protected:
 235   /*
 236    * To create a parent process task delivered from the child process through
 237    * IPC.
 238    */
 239   FileSystemTaskParentBase(FileSystemBase* aFileSystem,
 240                            const FileSystemParams& aParam,
 241                            FileSystemRequestParent* aParent);
 242
 243   virtual ~FileSystemTaskParentBase();
 244
 245   nsresult mErrorValue;
 246   RefPtr<FileSystemBase> mFileSystem;
 247   RefPtr<FileSystemRequestParent> mRequestParent;
 248   nsCOMPtr<nsIEventTarget> mBackgroundEventTarget;
 249 };
 250
 251 }  // namespace dom
 252 }  // namespace mozilla
 253
 254 #endif  // mozilla_dom_FileSystemTaskBase_h