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using System;
using System.Collections;
using System.Collections.Generic;
using Pfz.Caching;
using Pfz.Threading;
namespace Pfz.Collections
{
/// <summary>
/// This class is responsible for distributing a single enumerator
/// among many enumerator readers, considering such readers can
/// "loose" some of the items.
/// This is useful for senting, for example, web-cam frames. A high-speed
/// client can receive all frames, while a slow client can receive frame
/// 1, then frame 6, frame 12... but will still receive the "most recent"
/// frames.
/// You can inherit this class the the MultiClientEnumerator themselves
/// if you must only send the difference between frames.
/// </summary>
/// <typeparam name="T">
/// The type of the item that the original enumerator returns.
/// </typeparam>
public class EnumeratorDistributor<T>:
ThreadSafeExceptionAwareDisposable
where
T: class
{
internal HashSet<EnumeratorDistributorClient<T>> fClientEnumerators = new HashSet<EnumeratorDistributorClient<T>>();
/// <summary>
/// Creates a new Distributor over the given real enumerator.
/// </summary>
public EnumeratorDistributor(IFastEnumerator<T> baseEnumerator)
{
if (baseEnumerator == null)
throw new ArgumentNullException("baseEnumerator");
GCUtils.Collected += p_Collected;
BaseEnumerator = baseEnumerator;
UnlimitedThreadPool.Run(p_KeepReading);
}
/// <summary>
/// Disposes the base enumerator and the clients actually connected.
/// </summary>
protected override void Dispose(bool disposing)
{
if (disposing)
{
GCUtils.Collected -= p_Collected;
var baseEnumerator = BaseEnumerator;
if (baseEnumerator != null)
{
BaseEnumerator = null;
baseEnumerator.Dispose();
}
fActualValue = null;
var clients = fClientEnumerators;
if(clients != null)
{
fClientEnumerators = null;
// the normal lock can be used here, as our dispose is unabortable.
lock(DisposeLock)
foreach(var client in clients)
client.Dispose();
}
var disposedEvent = Disposed;
if (disposedEvent != null)
disposedEvent(this, EventArgs.Empty);
}
base.Dispose(disposing);
}
private void p_Collected()
{
var clients = fClientEnumerators;
if (clients == null)
{
GCUtils.Collected -= p_Collected;
return;
}
AbortSafe.UnabortableLock
(
clients,
delegate
{
// the if is here because there is a bug with trimexcess in empty hashsets,
// as the next foreach will throw an exception.
// This bug is already reported and should be corrected in future versions.
if (clients.Count > 0)
clients.TrimExcess();
}
);
}
/// <summary>
/// Gets the BaseEnumerator used by this distributor.
/// </summary>
public IFastEnumerator<T> BaseEnumerator { get; private set; }
/// <summary>
/// Called when this object is disposed.
/// </summary>
public event EventHandler Disposed;
private volatile T fActualValue;
/// <summary>
/// Gets the Actual value without waiting.
/// </summary>
public T ActualValue
{
get
{
return fActualValue;
}
}
private void p_KeepReading()
{
try
{
var baseEnumerator = BaseEnumerator;
while(true)
{
if (WasDisposed)
return;
var actualValue = baseEnumerator.GetNext();
fActualValue = actualValue;
AbortSafe.Lock
(
DisposeLock,
delegate
{
foreach(var client in fClientEnumerators)
client.fEvent.Set();
}
);
if (actualValue == null)
{
Dispose();
return;
}
}
}
catch(Exception exception)
{
if (!WasDisposed)
Dispose(exception);
}
}
/// <summary>
/// Creates a client for this enumerator.
/// Inheritors can initialize additional information before returning
/// the enumerator client to you.
/// </summary>
public virtual EnumeratorDistributorClient<T> CreateClient()
{
return new EnumeratorDistributorClient<T>(this);
}
}
}
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I started to program computers when I was 11 years old, as a hobbyist, programming in AMOS Basic and Blitz Basic for Amiga.
At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0).
Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods.
At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do their work easier, faster and with less errors.
Want more info or simply want to contact me?
Take a look at:
http://paulozemek.azurewebsites.net/
Or e-mail me at: paulozemek@outlook.com
Codeproject MVP 2012, 2015 & 2016
Microsoft MVP 2013-2014 (in October 2014 I started working at Microsoft, so I can't be a Microsoft MVP anymore).