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https://github.com/fadden/6502bench.git
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178 lines
6.8 KiB
C#
178 lines
6.8 KiB
C#
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/*
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* Copyright 2018 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Diagnostics;
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using System.Runtime.Remoting.Lifetime;
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using System.Security.Permissions;
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namespace SourceGen.Sandbox {
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/// <summary>
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/// This wraps a MarshalByRefObject instance with a "sponsor". This
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/// is necessary because objects created by the host in the plugin
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/// AppDomain aren't strongly referenced across the boundary (the two
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/// AppDomains have independent garbage collection). Because the plugin
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/// AppDomain can't know when the host AppDomain discards its objects,
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/// it will discard remote-proxied objects on its side after a period of disuse.
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///
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/// The ISponsor/ILease mechanism provides a way for the host-side object
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/// to define the lifespan of the plugin-side objects. The object
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/// manager in the plugin AppDomain will invoke Renewal() back in the host-side
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/// AppDomain.
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/// </summary>
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[SecurityPermission(SecurityAction.Demand, Infrastructure = true)]
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class Sponsor<T> : MarshalByRefObject, ISponsor, IDisposable where T : MarshalByRefObject {
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/// <summary>
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/// The object we've wrapped.
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/// </summary>
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private T mObj;
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/// <summary>
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/// For IDisposable.
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/// </summary>
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private bool mDisposed = false;
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// For debugging, track the last renewal time.
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private DateTime mLastRenewal = DateTime.Now;
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public T Instance {
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get {
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if (mDisposed) {
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throw new ObjectDisposedException("Sponsor was disposed");
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} else {
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return mObj;
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}
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}
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}
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public Sponsor(T obj) {
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mObj = obj;
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// Get the lifetime service lease from the MarshalByRefObject,
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// and register ourselves as a sponsor.
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ILease lease = (ILease)obj.GetLifetimeService();
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lease.Register(this);
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Debug.WriteLine(DateTime.Now.ToString("HH:mm:ss") + "|Sponsor created; initLt=" +
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lease.InitialLeaseTime + " renOC=" + lease.RenewOnCallTime +
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" spon=" + lease.SponsorshipTimeout);
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}
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public bool CheckLease() {
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try {
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ILease lease = (ILease)mObj.GetLifetimeService();
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if (lease.CurrentState != LeaseState.Active) {
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Debug.WriteLine("WARNING: lease has expired for " + mObj);
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return false;
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}
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} catch (System.Runtime.Remoting.RemotingException ex) {
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Debug.WriteLine("WARNING: remote object gone: " + ex.Message);
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return false;
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}
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return true;
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}
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/// <summary>
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/// Extends the lease time for the wrapped object. This is called
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/// from the plugin AppDomain, but executes on the host AppDomain.
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/// </summary>
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[SecurityPermissionAttribute(SecurityAction.LinkDemand,
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Flags = SecurityPermissionFlag.Infrastructure)]
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TimeSpan ISponsor.Renewal(ILease lease) {
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DateTime now = DateTime.Now;
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Debug.WriteLine(DateTime.Now.ToString("HH:mm:ss") + "|Lease renewal for " + mObj +
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", last renewed " + (now - mLastRenewal) + " sec ago; renewing for " +
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lease.RenewOnCallTime + " (host id=" + AppDomain.CurrentDomain.Id + ")");
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mLastRenewal = now;
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if (mDisposed) {
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// Shouldn't happen -- we should be unregistered -- but I
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// don't know if multiple threads are involved.
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Debug.WriteLine("WARNING: attempted to renew a disposed Sponsor");
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return TimeSpan.Zero;
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} else {
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// Use the lease's RenewOnCallTime.
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return lease.RenewOnCallTime;
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}
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}
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/// <summary>
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/// Finalizer. Required for IDisposable.
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/// </summary>
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~Sponsor() {
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Dispose(false);
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}
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/// <summary>
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/// Generic IDisposable implementation.
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/// </summary>
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public void Dispose() {
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// Dispose of unmanaged resources.
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Dispose(true);
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// Suppress finalization.
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GC.SuppressFinalize(this);
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}
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/// <summary>
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/// Destroys the Sponsor, if one was created.
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/// </summary>
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/// <param name="disposing">True if called from Dispose(), false if from finalizer.</param>
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protected virtual void Dispose(bool disposing) {
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if (mDisposed) {
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return;
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}
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Debug.WriteLine("Sponsor.Dispose(disposing=" + disposing + ")");
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// If this is a managed object, call its Dispose method.
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if (disposing) {
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if (mObj is IDisposable) {
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((IDisposable)mObj).Dispose();
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}
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}
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// Remove ourselves from the lifetime service.
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// NOTE: if you see this blowing up at app shutdown, it's because you didn't
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// call Dispose() on the DomainManager.
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object leaseObj;
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try {
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leaseObj = mObj.GetLifetimeService();
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} catch (Exception ex) {
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// This seems to happen when we shut down without having disposed of the
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// AppDomain, probably when a Sponsor's finalizer runs before the
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// DomainManager's finalizer. Sometimes it also happens when you seem to
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// be doing everything right, though this seems to correspond with a lack
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// of lease renewal messages (i.e. something is really wrong as the other end).
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//
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// I think failures here can be ignored, since it's just failure to clean up
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// something that doesn't exist.
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//
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// Sometimes it's:
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// RemotingException: Object '---' has been disconnected or does not exist at the server.
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Debug.WriteLine("WARNING: GetLifetimeService failed: " + ex.Message);
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leaseObj = null;
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}
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if (leaseObj is ILease) {
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ILease lease = (ILease)leaseObj;
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lease.Unregister(this);
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}
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mDisposed = true;
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}
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}
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}
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