sync/api/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_API_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
   6 #define SYNC_API_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/api/attachments/attachment_service.h"
  16 #include "sync/base/sync_export.h"
  17
  18 namespace syncer {
  19
  20 class SyncData;
  21
  22 // AttachmentServiceProxy wraps an AttachmentService allowing multiple threads
  23 // to share the wrapped AttachmentService and invoke its methods in the
  24 // appropriate thread.
  25 //
  26 // Callbacks passed to methods on this class will be invoked in the same thread
  27 // from which the method was called.
  28 //
  29 // This class does not own its wrapped AttachmentService object.  This class
  30 // holds a WeakPtr to the wrapped object.  Once the the wrapped object is
  31 // destroyed, method calls on this object will be no-ops.
  32 //
  33 // Users of this class should take care to destroy the wrapped object on the
  34 // correct thread (wrapped_task_runner).
  35 //
  36 // This class is thread-safe and is designed to be passed by const-ref.
  37 class SYNC_EXPORT AttachmentServiceProxy : public AttachmentService {
  38  public:
  39   // Default copy and assignment are welcome.
  40
  41   // Construct an invalid AttachmentServiceProxy.
  42   AttachmentServiceProxy();
  43
  44   // Construct an AttachmentServiceProxy that forwards calls to |wrapped| on the
  45   // |wrapped_task_runner| thread.
  46   //
  47   // Note, this object does not own |wrapped|.  When |wrapped| is destroyed,
  48   // calls to this object become no-ops.
  49   AttachmentServiceProxy(
  50       const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
  51       const base::WeakPtr<syncer::AttachmentService>& wrapped);
  52
  53   virtual ~AttachmentServiceProxy();
  54
  55   // AttachmentService implementation.
  56   virtual void GetOrDownloadAttachments(
  57       const AttachmentIdList& attachment_ids,
  58       const GetOrDownloadCallback& callback) OVERRIDE;
  59   virtual void DropAttachments(const AttachmentIdList& attachment_ids,
  60                                const DropCallback& callback) OVERRIDE;
  61   virtual void StoreAttachments(const AttachmentList& attachment,
  62                                 const StoreCallback& callback) OVERRIDE;
  63
  64  protected:
  65   // Core does the work of proxying calls to AttachmentService methods from one
  66   // thread to another so AttachmentServiceProxy can be an easy-to-use,
  67   // non-ref-counted A ref-counted class.
  68   //
  69   // Callback from AttachmentService are proxied back using free functions
  70   // defined in the .cc file (ProxyFooCallback functions).
  71   //
  72   // Core is ref-counted because we want to allow AttachmentServiceProxy to be
  73   // copy-constructable while allowing for different implementations of Core
  74   // (e.g. one type of core might own the wrapped AttachmentService).
  75   //
  76   // Calls to objects of this class become no-ops once its wrapped object is
  77   // destroyed.
  78   class SYNC_EXPORT Core : public AttachmentService,
  79                            public base::RefCountedThreadSafe<Core> {
  80    public:
  81     // Construct an AttachmentServiceProxyCore that forwards calls to |wrapped|.
  82     Core(const base::WeakPtr<syncer::AttachmentService>& wrapped);
  83
  84     // AttachmentService implementation.
  85     virtual void GetOrDownloadAttachments(
  86         const AttachmentIdList& attachment_ids,
  87         const GetOrDownloadCallback& callback) OVERRIDE;
  88     virtual void DropAttachments(const AttachmentIdList& attachment_ids,
  89                                  const DropCallback& callback) OVERRIDE;
  90     virtual void StoreAttachments(const AttachmentList& attachment,
  91                                   const StoreCallback& callback) OVERRIDE;
  92
  93    protected:
  94     friend class base::RefCountedThreadSafe<Core>;
  95     virtual ~Core();
  96
  97    private:
  98     base::WeakPtr<AttachmentService> wrapped_;
  99
 100     DISALLOW_COPY_AND_ASSIGN(Core);
 101   };
 102
 103   // Used in tests to create an AttachmentServiceProxy with a custom Core.
 104   AttachmentServiceProxy(
 105       const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
 106       const scoped_refptr<Core>& core);
 107
 108  private:
 109   scoped_refptr<base::SequencedTaskRunner> wrapped_task_runner_;
 110   scoped_refptr<Core> core_;
 111 };
 112
 113 }  // namespace syncer
 114
 115 #endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_