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482 lines
18 KiB
C++
482 lines
18 KiB
C++
//*********************************************************
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//
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// Copyright (c) Microsoft. All rights reserved.
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// THIS CODE IS PROVIDED *AS IS* WITHOUT WARRANTY OF
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// ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING ANY
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// IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR
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// PURPOSE, MERCHANTABILITY, OR NON-INFRINGEMENT.
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//
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//*********************************************************
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//
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// SuspensionManager.cpp
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// Implementation of the SuspensionManager class
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//
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#include "pch.h"
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#include "SuspensionManager.h"
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#include <collection.h>
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#include <algorithm>
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using namespace SDKSample::Common;
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using namespace Concurrency;
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using namespace Platform;
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using namespace Platform::Collections;
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using namespace Windows::Foundation;
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using namespace Windows::Foundation::Collections;
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using namespace Windows::Storage;
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using namespace Windows::Storage::FileProperties;
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using namespace Windows::Storage::Streams;
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using namespace Windows::UI::Xaml;
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using namespace Windows::UI::Xaml::Controls;
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using namespace Windows::UI::Xaml::Interop;
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namespace
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{
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Map<String^, Object^>^ _sessionState = ref new Map<String^, Object^>();
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String^ sessionStateFilename = "_sessionState.dat";
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// Forward declarations for object object read / write support
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void WriteObject(Windows::Storage::Streams::DataWriter^ writer, Platform::Object^ object);
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Platform::Object^ ReadObject(Windows::Storage::Streams::DataReader^ reader);
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}
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/// <summary>
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/// Provides access to global session state for the current session. This state is serialized by
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/// <see cref="SaveAsync"/> and restored by <see cref="RestoreAsync"/> which require values to be
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/// one of the following: boxed values including integers, floating-point singles and doubles,
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/// wide characters, boolean, Strings and Guids, or Map<String^, Object^> where map values are
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/// subject to the same constraints. Session state should be as compact as possible.
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/// </summary>
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IMap<String^, Object^>^ SuspensionManager::SessionState::get(void)
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{
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return _sessionState;
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}
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/// <summary>
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/// Wrap a WeakReference as a reference object for use in a collection.
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/// </summary>
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private ref class WeakFrame sealed
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{
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private:
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WeakReference _frameReference;
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internal:
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WeakFrame(Frame^ frame) { _frameReference = frame; }
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property Frame^ ResolvedFrame
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{
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Frame^ get(void) { return _frameReference.Resolve<Frame>(); }
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};
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};
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namespace
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{
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std::vector<WeakFrame^> _registeredFrames;
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DependencyProperty^ FrameSessionStateKeyProperty =
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DependencyProperty::RegisterAttached("_FrameSessionStateKeyProperty",
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TypeName(String::typeid), TypeName(SuspensionManager::typeid), nullptr);
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DependencyProperty^ FrameSessionStateProperty =
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DependencyProperty::RegisterAttached("_FrameSessionStateProperty",
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TypeName(IMap<String^, Object^>::typeid), TypeName(SuspensionManager::typeid), nullptr);
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}
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/// <summary>
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/// Registers a <see cref="Frame"/> instance to allow its navigation history to be saved to
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/// and restored from <see cref="SessionState"/>. Frames should be registered once
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/// immediately after creation if they will participate in session state management. Upon
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/// registration if state has already been restored for the specified key
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/// the navigation history will immediately be restored. Subsequent invocations of
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/// <see cref="RestoreAsync(String)"/> will also restore navigation history.
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/// </summary>
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/// <param name="frame">An instance whose navigation history should be managed by
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/// <see cref="SuspensionManager"/></param>
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/// <param name="sessionStateKey">A unique key into <see cref="SessionState"/> used to
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/// store navigation-related information.</param>
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void SuspensionManager::RegisterFrame(Frame^ frame, String^ sessionStateKey)
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{
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if (frame->GetValue(FrameSessionStateKeyProperty) != nullptr)
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{
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throw ref new FailureException("Frames can only be registered to one session state key");
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}
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if (frame->GetValue(FrameSessionStateProperty) != nullptr)
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{
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throw ref new FailureException("Frames must be either be registered before accessing frame session state, or not registered at all");
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}
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// Use a dependency property to associate the session key with a frame, and keep a list of frames whose
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// navigation state should be managed
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frame->SetValue(FrameSessionStateKeyProperty, sessionStateKey);
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_registeredFrames.insert(_registeredFrames.begin(), ref new WeakFrame(frame));
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// Check to see if navigation state can be restored
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RestoreFrameNavigationState(frame);
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}
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/// <summary>
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/// Disassociates a <see cref="Frame"/> previously registered by <see cref="RegisterFrame"/>
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/// from <see cref="SessionState"/>. Any navigation state previously captured will be
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/// removed.
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/// </summary>
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/// <param name="frame">An instance whose navigation history should no longer be
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/// managed.</param>
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void SuspensionManager::UnregisterFrame(Frame^ frame)
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{
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// Remove session state and remove the frame from the list of frames whose navigation
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// state will be saved (along with any weak references that are no longer reachable)
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auto key = safe_cast<String^>(frame->GetValue(FrameSessionStateKeyProperty));
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if (SessionState->HasKey(key)) SessionState->Remove(key);
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_registeredFrames.erase(
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std::remove_if(_registeredFrames.begin(), _registeredFrames.end(), [=](WeakFrame^& e)
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{
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auto testFrame = e->ResolvedFrame;
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return testFrame == nullptr || testFrame == frame;
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}),
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_registeredFrames.end()
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);
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}
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/// <summary>
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/// Provides storage for session state associated with the specified <see cref="Frame"/>.
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/// Frames that have been previously registered with <see cref="RegisterFrame"/> have
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/// their session state saved and restored automatically as a part of the global
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/// <see cref="SessionState"/>. Frames that are not registered have transient state
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/// that can still be useful when restoring pages that have been discarded from the
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/// navigation cache.
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/// </summary>
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/// <remarks>Apps may choose to rely on <see cref="LayoutAwarePage"/> to manage
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/// page-specific state instead of working with frame session state directly.</remarks>
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/// <param name="frame">The instance for which session state is desired.</param>
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/// <returns>A collection of state subject to the same serialization mechanism as
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/// <see cref="SessionState"/>.</returns>
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IMap<String^, Object^>^ SuspensionManager::SessionStateForFrame(Frame^ frame)
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{
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auto frameState = safe_cast<IMap<String^, Object^>^>(frame->GetValue(FrameSessionStateProperty));
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if (frameState == nullptr)
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{
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auto frameSessionKey = safe_cast<String^>(frame->GetValue(FrameSessionStateKeyProperty));
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if (frameSessionKey != nullptr)
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{
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// Registered frames reflect the corresponding session state
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if (!_sessionState->HasKey(frameSessionKey))
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{
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_sessionState->Insert(frameSessionKey, ref new Map<String^, Object^>());
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}
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frameState = safe_cast<IMap<String^, Object^>^>(_sessionState->Lookup(frameSessionKey));
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}
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else
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{
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// Frames that aren't registered have transient state
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frameState = ref new Map<String^, Object^>();
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}
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frame->SetValue(FrameSessionStateProperty, frameState);
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}
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return frameState;
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}
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void SuspensionManager::RestoreFrameNavigationState(Frame^ frame)
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{
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auto frameState = SessionStateForFrame(frame);
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if (frameState->HasKey("Navigation"))
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{
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frame->SetNavigationState(safe_cast<String^>(frameState->Lookup("Navigation")));
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}
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}
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void SuspensionManager::SaveFrameNavigationState(Frame^ frame)
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{
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auto frameState = SessionStateForFrame(frame);
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frameState->Insert("Navigation", frame->GetNavigationState());
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}
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/// <summary>
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/// Save the current <see cref="SessionState"/>. Any <see cref="Frame"/> instances
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/// registered with <see cref="RegisterFrame"/> will also preserve their current
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/// navigation stack, which in turn gives their active <see cref="Page"/> an opportunity
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/// to save its state.
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/// </summary>
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/// <returns>An asynchronous task that reflects when session state has been saved.</returns>
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task<void> SuspensionManager::SaveAsync(void)
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{
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// Save the navigation state for all registered frames
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for (auto&& weakFrame : _registeredFrames)
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{
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auto frame = weakFrame->ResolvedFrame;
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if (frame != nullptr) SaveFrameNavigationState(frame);
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}
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// Serialize the session state synchronously to avoid asynchronous access to shared
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// state
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auto sessionData = ref new InMemoryRandomAccessStream();
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auto sessionDataWriter = ref new DataWriter(sessionData->GetOutputStreamAt(0));
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WriteObject(sessionDataWriter, _sessionState);
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// Once session state has been captured synchronously, begin the asynchronous process
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// of writing the result to disk
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return task<unsigned int>(sessionDataWriter->StoreAsync()).then([=](unsigned int)
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{
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return sessionDataWriter->FlushAsync();
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}).then([=](bool flushSucceeded)
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{
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(void)flushSucceeded; // Unused parameter
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return ApplicationData::Current->LocalFolder->CreateFileAsync(sessionStateFilename,
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CreationCollisionOption::ReplaceExisting);
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}).then([=](StorageFile^ createdFile)
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{
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return createdFile->OpenAsync(FileAccessMode::ReadWrite);
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}).then([=](IRandomAccessStream^ newStream)
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{
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return RandomAccessStream::CopyAndCloseAsync(
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sessionData->GetInputStreamAt(0), newStream->GetOutputStreamAt(0));
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}).then([=](UINT64 copiedBytes)
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{
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(void)copiedBytes; // Unused parameter
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return;
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});
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}
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/// <summary>
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/// Restores previously saved <see cref="SessionState"/>. Any <see cref="Frame"/> instances
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/// registered with <see cref="RegisterFrame"/> will also restore their prior navigation
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/// state, which in turn gives their active <see cref="Page"/> an opportunity restore its
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/// state.
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/// </summary>
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/// <param name="version">A version identifier compared to the session state to prevent
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/// incompatible versions of session state from reaching app code. Saved state with a
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/// different version will be ignored, resulting in an empty <see cref="SessionState"/>
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/// dictionary.</param>
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/// <returns>An asynchronous task that reflects when session state has been read. The
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/// content of <see cref="SessionState"/> should not be relied upon until this task
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/// completes.</returns>
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task<void> SuspensionManager::RestoreAsync(void)
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{
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_sessionState->Clear();
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task<StorageFile^> getFileTask(ApplicationData::Current->LocalFolder->GetFileAsync(sessionStateFilename));
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return getFileTask.then([=](StorageFile^ stateFile)
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{
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task<BasicProperties^> getBasicPropertiesTask(stateFile->GetBasicPropertiesAsync());
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return getBasicPropertiesTask.then([=](BasicProperties^ stateFileProperties)
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{
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auto size = unsigned int(stateFileProperties->Size);
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if (size != stateFileProperties->Size) throw ref new FailureException("Session state larger than 4GB");
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task<IRandomAccessStreamWithContentType^> openReadTask(stateFile->OpenReadAsync());
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return openReadTask.then([=](IRandomAccessStreamWithContentType^ stateFileStream)
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{
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auto stateReader = ref new DataReader(stateFileStream);
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return task<unsigned int>(stateReader->LoadAsync(size)).then([=](unsigned int bytesRead)
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{
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(void)bytesRead; // Unused parameter
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// Deserialize the Session State
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Object^ content = ReadObject(stateReader);
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_sessionState = (Map<String^, Object^>^)content;
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// Restore any registered frames to their saved state
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for (auto&& weakFrame : _registeredFrames)
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{
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auto frame = weakFrame->ResolvedFrame;
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if (frame != nullptr)
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{
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frame->ClearValue(FrameSessionStateProperty);
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RestoreFrameNavigationState(frame);
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}
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}
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}, task_continuation_context::use_current());
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});
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});
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});
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}
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#pragma region Object serialization for a known set of types
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namespace
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{
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// Codes used for identifying serialized types
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enum StreamTypes {
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NullPtrType = 0,
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// Supported IPropertyValue types
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UInt8Type, UInt16Type, UInt32Type, UInt64Type, Int16Type, Int32Type, Int64Type,
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SingleType, DoubleType, BooleanType, Char16Type, GuidType, StringType,
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// Additional supported types
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StringToObjectMapType,
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// Marker values used to ensure stream integrity
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MapEndMarker
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};
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void WriteString(DataWriter^ writer, String^ string)
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{
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writer->WriteByte(StringType);
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writer->WriteUInt32(writer->MeasureString(string));
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writer->WriteString(string);
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}
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void WriteProperty(DataWriter^ writer, IPropertyValue^ propertyValue)
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{
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switch (propertyValue->Type)
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{
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case PropertyType::UInt8:
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writer->WriteByte(UInt8Type);
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writer->WriteByte(propertyValue->GetUInt8());
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return;
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case PropertyType::UInt16:
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writer->WriteByte(UInt16Type);
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writer->WriteUInt16(propertyValue->GetUInt16());
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return;
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case PropertyType::UInt32:
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writer->WriteByte(UInt32Type);
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writer->WriteUInt32(propertyValue->GetUInt32());
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return;
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case PropertyType::UInt64:
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writer->WriteByte(UInt64Type);
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writer->WriteUInt64(propertyValue->GetUInt64());
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return;
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case PropertyType::Int16:
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writer->WriteByte(Int16Type);
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writer->WriteUInt16(propertyValue->GetInt16());
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return;
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case PropertyType::Int32:
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writer->WriteByte(Int32Type);
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writer->WriteUInt32(propertyValue->GetInt32());
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return;
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case PropertyType::Int64:
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writer->WriteByte(Int64Type);
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writer->WriteUInt64(propertyValue->GetInt64());
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return;
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case PropertyType::Single:
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writer->WriteByte(SingleType);
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writer->WriteSingle(propertyValue->GetSingle());
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return;
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case PropertyType::Double:
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writer->WriteByte(DoubleType);
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writer->WriteDouble(propertyValue->GetDouble());
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return;
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case PropertyType::Boolean:
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writer->WriteByte(BooleanType);
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writer->WriteBoolean(propertyValue->GetBoolean());
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return;
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case PropertyType::Char16:
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writer->WriteByte(Char16Type);
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writer->WriteUInt16(propertyValue->GetChar16());
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return;
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case PropertyType::Guid:
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writer->WriteByte(GuidType);
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writer->WriteGuid(propertyValue->GetGuid());
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return;
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case PropertyType::String:
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WriteString(writer, propertyValue->GetString());
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return;
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default:
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throw ref new InvalidArgumentException("Unsupported property type");
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}
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}
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void WriteStringToObjectMap(DataWriter^ writer, IMap<String^, Object^>^ map)
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{
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writer->WriteByte(StringToObjectMapType);
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writer->WriteUInt32(map->Size);
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for (auto&& pair : map)
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{
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WriteObject(writer, pair->Key);
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WriteObject(writer, pair->Value);
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}
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writer->WriteByte(MapEndMarker);
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}
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void WriteObject(DataWriter^ writer, Object^ object)
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{
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if (object == nullptr)
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{
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writer->WriteByte(NullPtrType);
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return;
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}
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auto propertyObject = dynamic_cast<IPropertyValue^>(object);
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if (propertyObject != nullptr)
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{
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WriteProperty(writer, propertyObject);
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return;
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}
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auto mapObject = dynamic_cast<IMap<String^, Object^>^>(object);
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if (mapObject != nullptr)
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{
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WriteStringToObjectMap(writer, mapObject);
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return;
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}
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throw ref new InvalidArgumentException("Unsupported data type");
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}
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String^ ReadString(DataReader^ reader)
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{
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int length = reader->ReadUInt32();
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String^ string = reader->ReadString(length);
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return string;
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}
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IMap<String^, Object^>^ ReadStringToObjectMap(DataReader^ reader)
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{
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auto map = ref new Map<String^, Object^>();
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auto size = reader->ReadUInt32();
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for (unsigned int index = 0; index < size; index++)
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{
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auto key = safe_cast<String^>(ReadObject(reader));
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auto value = ReadObject(reader);
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map->Insert(key, value);
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}
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if (reader->ReadByte() != MapEndMarker)
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{
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throw ref new InvalidArgumentException("Invalid stream");
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}
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return map;
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}
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Object^ ReadObject(DataReader^ reader)
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{
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auto type = reader->ReadByte();
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switch (type)
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{
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case NullPtrType:
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return nullptr;
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case UInt8Type:
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return reader->ReadByte();
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case UInt16Type:
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return reader->ReadUInt16();
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case UInt32Type:
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return reader->ReadUInt32();
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case UInt64Type:
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return reader->ReadUInt64();
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case Int16Type:
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return reader->ReadInt16();
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case Int32Type:
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return reader->ReadInt32();
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case Int64Type:
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return reader->ReadInt64();
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case SingleType:
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return reader->ReadSingle();
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case DoubleType:
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return reader->ReadDouble();
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case BooleanType:
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return reader->ReadBoolean();
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case Char16Type:
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return (char16_t)reader->ReadUInt16();
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case GuidType:
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return reader->ReadGuid();
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case StringType:
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return ReadString(reader);
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case StringToObjectMapType:
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return ReadStringToObjectMap(reader);
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default:
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throw ref new InvalidArgumentException("Unsupported property type");
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}
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}
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}
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#pragma endregion
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