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using System;
using System.Collections.Generic;
namespace SharpCompress
{
internal class LazyReadOnlyCollection<T> : ICollection<T>
{
private readonly List<T> backing = new List<T>();
private readonly IEnumerator<T> source;
private bool fullyLoaded;
public LazyReadOnlyCollection(IEnumerable<T> source)
{
this.source = source.GetEnumerator();
}
private class LazyLoader : IEnumerator<T>
{
private readonly LazyReadOnlyCollection<T> lazyReadOnlyCollection;
private bool disposed;
private int index = -1;
internal LazyLoader(LazyReadOnlyCollection<T> lazyReadOnlyCollection)
{
this.lazyReadOnlyCollection = lazyReadOnlyCollection;
}
#region IEnumerator<T> Members
public T Current
{
get { return lazyReadOnlyCollection.backing[index]; }
}
#endregion
#region IDisposable Members
public void Dispose()
{
if (!disposed)
{
disposed = true;
}
}
#endregion
#region IEnumerator Members
object System.Collections.IEnumerator.Current
{
get { return Current; }
}
public bool MoveNext()
{
if (index + 1 < lazyReadOnlyCollection.backing.Count)
{
index++;
return true;
}
if (!lazyReadOnlyCollection.fullyLoaded && lazyReadOnlyCollection.source.MoveNext())
{
lazyReadOnlyCollection.backing.Add(lazyReadOnlyCollection.source.Current);
index++;
return true;
}
lazyReadOnlyCollection.fullyLoaded = true;
return false;
}
public void Reset()
{
throw new NotImplementedException();
}
#endregion
}
internal void EnsureFullyLoaded()
{
if (!fullyLoaded)
{
this.ForEach(x => { });
fullyLoaded = true;
}
}
internal IEnumerable<T> GetLoaded()
{
return backing;
}
#region ICollection<T> Members
public void Add(T item)
{
throw new NotImplementedException();
}
public void Clear()
{
throw new NotImplementedException();
}
public bool Contains(T item)
{
EnsureFullyLoaded();
return backing.Contains(item);
}
public void CopyTo(T[] array, int arrayIndex)
{
EnsureFullyLoaded();
backing.CopyTo(array, arrayIndex);
}
public int Count
{
get
{
EnsureFullyLoaded();
return backing.Count;
}
}
public bool IsReadOnly
{
get { return true; }
}
public bool Remove(T item)
{
throw new NotImplementedException();
}
#endregion
#region IEnumerable<T> Members
//TODO check for concurrent access
public IEnumerator<T> GetEnumerator()
{
return new LazyLoader(this);
}
#endregion
#region IEnumerable Members
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
#endregion
}
}
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