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using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;
using Pfz.Threading;
namespace Pfz.Caching
{
/// <summary>
/// A collection that only keeps weak-references to its items.
/// Ideal if at some point you only need to do a for-each over all the
/// non-collected items. Use WeakHashSet if you need to remove the items
/// or call Contains frequently.
/// </summary>
/// <typeparam name="T"></typeparam>
[Serializable]
public class WeakCollection<T>:
ReaderWriterSafeDisposable,
ISerializable,
ICollection<T>,
IGarbageCollectionAware
where
T: class
{
#region Private fields
private static readonly Comparison<GCHandle> _SortHandlesDelegate = _SortHandles;
private GCHandle[] _handles;
#endregion
#region Constructors
/// <summary>
/// Creates an empty weak-list.
/// </summary>
public WeakCollection():
this(32)
{
}
/// <summary>
/// Creates an empty weak-list using the given minCapacity to it.
/// </summary>
/// <param name="initialCapacity">The initialCapacity of the list. The default value is 32.</param>
public WeakCollection(int initialCapacity)
{
if (initialCapacity < 1)
throw new ArgumentOutOfRangeException("initialCapacity", "The initial accepted capacity value is 1.");
_handles = new GCHandle[initialCapacity];
GCUtils.RegisterForCollectedNotification(this);
}
#endregion
#region Dispose
/// <summary>
/// Releases all handles.
/// </summary>
protected override void Dispose(bool disposing)
{
// if the dispose was called manullay, we must unregister ourselves from the GCUtils.Collected method.
// we don't need to do this if this object is being collected, as the Collected event is also we and, so,
// it was already removed from there.
if (disposing)
GCUtils.UnregisterFromCollectedNotification(this);
// here we will free all allocated handles. After all, even if the objects can be collected, the
// handles must be freed.
var handles = _handles;
if (handles != null)
{
int count = handles.Length;
for (int i=0; i<count; i++)
{
var handle = handles[i];
if (handle.IsAllocated)
handle.Free();
}
_handles = null;
}
base.Dispose(disposing);
}
#endregion
#region _Collected
void IGarbageCollectionAware.OnCollected()
{
using(DisposeLock.WriteLock())
{
if (WasDisposed)
{
GCUtils.UnregisterFromCollectedNotification(this);
return;
}
int allocated = 0;
int count = Count;
for(int i=0; i<count; i++)
{
var handle = _handles[i];
if (handle.IsAllocated && handle.Target != null)
allocated ++;
}
int minCapacity = count / 2;
if (minCapacity < 32)
minCapacity = 32;
if (allocated < minCapacity)
allocated = minCapacity;
if (allocated != _handles.Length)
{
var newHandles = new GCHandle[allocated];
try
{
}
finally
{
int newIndex = 0;
for(int i=0; i<count; i++)
{
var handle = _handles[i];
if (!handle.IsAllocated)
continue;
var target = handle.Target;
if (target == null)
handle.Free();
else
{
newHandles[newIndex] = handle;
newIndex++;
}
}
for(int i=count; i<_handles.Length; i++)
{
var handle = _handles[i];
if (handle.IsAllocated)
handle.Free();
}
Count = newIndex;
_handles = newHandles;
}
}
}
}
#endregion
#region Properties
#region Count
/// <summary>
/// Gets an approximate count of the items added.
/// </summary>
public int Count { get; private set; }
#endregion
#endregion
#region Methods
#region Clear
/// <summary>
/// Clears all the items in the list.
/// </summary>
public void Clear()
{
using(DisposeLock.WriteLock())
{
CheckUndisposed();
Count = 0;
}
}
#endregion
#region Add
/// <summary>
/// Adds an item to the list.
/// </summary>
public void Add(T item)
{
if (item == null)
throw new ArgumentNullException("item");
using(DisposeLock.WriteLock())
{
CheckUndisposed();
int count = Count;
if (count == _handles.Length)
{
bool mustReturn = false;
try
{
}
finally
{
Array.Sort(_handles, _SortHandlesDelegate);
for(int i=0; i<count; i++)
{
var handle1 = _handles[i];
if (handle1.Target == null)
{
handle1.Target = item;
Count = i+1;
mustReturn = true;
break;
}
}
if (!mustReturn)
Array.Resize(ref _handles, count * 2);
}
if (mustReturn)
return;
}
var handle = _handles[count];
if (handle.IsAllocated)
handle.Target = item;
else
{
try
{
}
finally
{
_handles[count] = GCHandle.Alloc(item, GCHandleType.Weak);
}
}
Count++;
}
}
#endregion
#region ToList
/// <summary>
/// Gets a strong-list with all the non-collected items present
/// in this list.
/// </summary>
public List<T> ToList()
{
List<T> result = new List<T>();
using(DisposeLock.ReadLock())
{
CheckUndisposed();
int count = Count;
for (int i=0; i<count; i++)
{
object target = _handles[i].Target;
if (target != null)
result.Add((T)target);
}
}
return result;
}
#endregion
#region Contains
/// <summary>
/// Returns true if an item exists in the collection, false otherwise.
/// </summary>
public bool Contains(T item)
{
if (item == null)
throw new ArgumentNullException("item");
using(DisposeLock.ReadLock())
return _IndexOf(item) != -1;
}
#endregion
#region _IndexOf
private int _IndexOf(T item)
{
CheckUndisposed();
int count = Count;
for (int i=0; i<count; i++)
{
GCHandle handle = _handles[i];
if (handle.Target == item)
return i;
}
return -1;
}
#endregion
#region Remove
/// <summary>
/// Tries to remove an item from this list and returns if it was
/// found and removed. Note that the Count and the following items
/// are not automatically updated, as this will only happen in the next
/// garbage collection.
/// </summary>
public bool Remove(T item)
{
using(DisposeLock.WriteLock())
{
int index = _IndexOf(item);
if (index != -1)
{
_handles[index].Target = null;
if (index == Count-1)
Count = index;
return true;
}
}
return false;
}
#endregion
#region RemoveLast
/// <summary>
/// Removes the last item from the list and return it.
/// It the list is empty, returns null.
/// </summary>
public T RemoveLast()
{
using(var upgradeableLock = DisposeLock.UpgradeableLock())
{
int count = Count;
for(int i=count-1; i>=0; i--)
{
var handle = _handles[i];
var target = handle.Target;
if (target != null)
{
upgradeableLock.Upgrade();
handle.Target = null;
Count = i;
return (T)target;
}
}
}
return null;
}
#endregion
#region GetEnumerator
/// <summary>
/// Gets an enumerator over the non-collected items of this
/// list.
/// </summary>
public IEnumerator<T> GetEnumerator()
{
return ToList().GetEnumerator();
}
#endregion
#region _SortHandles
private static int _SortHandles(GCHandle a, GCHandle b)
{
if (a.Target == null)
{
if (b.Target == null)
return 0;
return 1;
}
if (b.Target == null)
return -1;
return 0;
}
#endregion
#endregion
#region Interfaces
#region ISerializable Members
/// <summary>
/// Creates the WeakList from the serialization info.
/// </summary>
protected WeakCollection(SerializationInfo info, StreamingContext context):
this(32)
{
}
/// <summary>
/// Creates serialization info.
/// </summary>
protected virtual void GetObjectData(SerializationInfo info, StreamingContext context)
{
}
void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
{
GetObjectData(info, context);
}
#endregion
#region ICollection<T> Members
void ICollection<T>.CopyTo(T[] array, int arrayIndex)
{
ToList().CopyTo(array, arrayIndex);
}
bool ICollection<T>.IsReadOnly
{
get
{
return false;
}
}
#endregion
#region IEnumerable Members
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
#endregion
#endregion
}
}
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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).