sync/internal_api/public/attachments/attachment_service_proxy.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
   6 #define SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/callback.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/memory/weak_ptr.h"
  12 #include "base/sequenced_task_runner.h"
  13 #include "base/task_runner.h"
  14 #include "sync/api/attachments/attachment.h"
  15 #include "sync/base/sync_export.h"
  16 #include "sync/internal_api/public/attachments/attachment_service.h"
  17
  18 namespace syncer {
  19
  20 // AttachmentServiceProxy wraps an AttachmentService allowing multiple threads
  21 // to share the wrapped AttachmentService and invoke its methods in the
  22 // appropriate thread.
  23 //
  24 // Callbacks passed to methods on this class will be invoked in the same thread
  25 // from which the method was called.
  26 //
  27 // This class does not own its wrapped AttachmentService object.  This class
  28 // holds a WeakPtr to the wrapped object.  Once the the wrapped object is
  29 // destroyed, method calls on this object will be no-ops.
  30 //
  31 // Users of this class should take care to destroy the wrapped object on the
  32 // correct thread (wrapped_task_runner).
  33 //
  34 // This class is thread-safe and is designed to be passed by const-ref.
  35 class SYNC_EXPORT AttachmentServiceProxy : public AttachmentService {
  36  public:
  37   // Default copy and assignment are welcome.
  38
  39   // Construct an invalid AttachmentServiceProxy.
  40   AttachmentServiceProxy();
  41
  42   // Construct an AttachmentServiceProxy that forwards calls to |wrapped| on the
  43   // |wrapped_task_runner| thread.
  44   //
  45   // Note, this object does not own |wrapped|.  When |wrapped| is destroyed,
  46   // calls to this object become no-ops.
  47   AttachmentServiceProxy(
  48       const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
  49       const base::WeakPtr<syncer::AttachmentService>& wrapped);
  50
  51   ~AttachmentServiceProxy() override;
  52
  53   void GetOrDownloadAttachments(const AttachmentIdList& attachment_ids,
  54                                 const GetOrDownloadCallback& callback) override;
  55   void UploadAttachments(const AttachmentIdList& attachment_ids) override;
  56
  57  protected:
  58   // Core does the work of proxying calls to AttachmentService methods from one
  59   // thread to another so AttachmentServiceProxy can be an easy-to-use,
  60   // non-ref-counted A ref-counted class.
  61   //
  62   // Callback from AttachmentService are proxied back using free functions
  63   // defined in the .cc file (ProxyFooCallback functions).
  64   //
  65   // Core is ref-counted because we want to allow AttachmentServiceProxy to be
  66   // copy-constructable while allowing for different implementations of Core
  67   // (e.g. one type of core might own the wrapped AttachmentService).
  68   //
  69   // Calls to objects of this class become no-ops once its wrapped object is
  70   // destroyed.
  71   class SYNC_EXPORT Core : public AttachmentService,
  72                            public base::RefCountedThreadSafe<Core> {
  73    public:
  74     // Construct an AttachmentServiceProxyCore that forwards calls to |wrapped|.
  75     Core(const base::WeakPtr<syncer::AttachmentService>& wrapped);
  76
  77     // AttachmentService implementation.
  78     void GetOrDownloadAttachments(
  79         const AttachmentIdList& attachment_ids,
  80         const GetOrDownloadCallback& callback) override;
  81     void UploadAttachments(const AttachmentIdList& attachment_ids) override;
  82
  83    protected:
  84     friend class base::RefCountedThreadSafe<Core>;
  85     ~Core() override;
  86
  87    private:
  88     base::WeakPtr<AttachmentService> wrapped_;
  89
  90     DISALLOW_COPY_AND_ASSIGN(Core);
  91   };
  92
  93   // Used in tests to create an AttachmentServiceProxy with a custom Core.
  94   AttachmentServiceProxy(
  95       const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
  96       const scoped_refptr<Core>& core);
  97
  98  private:
  99   scoped_refptr<base::SequencedTaskRunner> wrapped_task_runner_;
 100   scoped_refptr<Core> core_;
 101 };
 102
 103 }  // namespace syncer
 104
 105 #endif  // SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_