// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using NewLife.Reflection;
namespace System.Linq
{
public static partial class EnumerableEx
{
#region -- Share --
/// <summary>
/// Creates a buffer with a shared view over the source sequence, causing each enumerator to fetch the next element from the source sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Buffer enabling each enumerator to retrieve elements from the shared source sequence.</returns>
/// <example>
/// var rng = Enumerable.Range(0, 10).Share();
///
/// var e1 = rng.GetEnumerator(); // Both e1 and e2 will consume elements from
/// var e2 = rng.GetEnumerator(); // the source sequence.
///
/// Assert.IsTrue(e1.MoveNext());
/// Assert.AreEqual(0, e1.Current);
///
/// Assert.IsTrue(e1.MoveNext());
/// Assert.AreEqual(1, e1.Current);
///
/// Assert.IsTrue(e2.MoveNext()); // e2 "steals" element 2
/// Assert.AreEqual(2, e2.Current);
///
/// Assert.IsTrue(e1.MoveNext()); // e1 can't see element 2
/// Assert.AreEqual(3, e1.Current);
/// </example>
public static IBuffer<TSource> Share<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return new SharedBuffer<TSource>(source.GetEnumerator());
}
/// <summary>
/// Shares the source sequence within a selector function where each enumerator can fetch the next element from the source sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TResult">Result sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">Selector function with shared access to the source sequence for each enumerator.</param>
/// <returns>Sequence resulting from applying the selector function to the shared view over the source sequence.</returns>
public static IEnumerable<TResult> Share<TSource, TResult>(this IEnumerable<TSource> source, Func<IEnumerable<TSource>, IEnumerable<TResult>> selector)
{
if (source == null)
throw new ArgumentNullException("source");
if (selector == null)
throw new ArgumentNullException("selector");
return Create<TResult>(() => selector(source.Share()).GetEnumerator());
}
#region - class SharedBuffer -
class SharedBuffer<T> : IBuffer<T>
{
private IEnumerator<T> _source;
private bool _disposed;
public SharedBuffer(IEnumerator<T> source)
{
_source = source;
}
public IEnumerator<T> GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
return GetEnumerator_();
}
private IEnumerator<T> GetEnumerator_()
{
while (true)
{
if (_disposed)
throw new ObjectDisposedException("");
var hasValue = default(bool);
var current = default(T);
lock (_source)
{
hasValue = _source.MoveNext();
if (hasValue)
current = _source.Current;
}
if (hasValue)
yield return current;
else
break;
}
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
return GetEnumerator();
}
public void Dispose()
{
lock (_source)
{
if (!_disposed)
{
_source.Dispose();
_source = null;
}
_disposed = true;
}
}
}
#endregion
#endregion
#region -- Publish --
/// <summary>
/// Creates a buffer with a view over the source sequence, causing each enumerator to obtain access to the remainder of the sequence from the current index in the buffer.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Buffer enabling each enumerator to retrieve elements from the shared source sequence, starting from the index at the point of obtaining the enumerator.</returns>
/// <example>
/// var rng = Enumerable.Range(0, 10).Publish();
///
/// var e1 = rng.GetEnumerator(); // e1 has a view on the source starting from element 0
///
/// Assert.IsTrue(e1.MoveNext());
/// Assert.AreEqual(0, e1.Current);
///
/// Assert.IsTrue(e1.MoveNext());
/// Assert.AreEqual(1, e1.Current);
///
/// var e2 = rng.GetEnumerator();
///
/// Assert.IsTrue(e2.MoveNext()); // e2 has a view on the source starting from element 2
/// Assert.AreEqual(2, e2.Current);
///
/// Assert.IsTrue(e1.MoveNext()); // e1 continues to enumerate over its view
/// Assert.AreEqual(2, e1.Current);
/// </example>
public static IBuffer<TSource> Publish<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return new PublishedBuffer<TSource>(source.GetEnumerator());
}
/// <summary>
/// Publishes the source sequence within a selector function where each enumerator can obtain a view over a tail of the source sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TResult">Result sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">Selector function with published access to the source sequence for each enumerator.</param>
/// <returns>Sequence resulting from applying the selector function to the published view over the source sequence.</returns>
public static IEnumerable<TResult> Publish<TSource, TResult>(this IEnumerable<TSource> source, Func<IEnumerable<TSource>, IEnumerable<TResult>> selector)
{
if (source == null)
throw new ArgumentNullException("source");
if (selector == null)
throw new ArgumentNullException("selector");
return Create<TResult>(() => selector(source.Publish()).GetEnumerator());
}
#region - class PublishedBuffer -
class PublishedBuffer<T> : IBuffer<T>
{
private IEnumerator<T> _source;
private RefCountList<T> _buffer;
private bool _stopped;
private Exception _error;
private bool _disposed;
public PublishedBuffer(IEnumerator<T> source)
{
_buffer = new RefCountList<T>(0);
_source = source;
}
public IEnumerator<T> GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
var i = default(int);
lock (_source)
{
i = _buffer.Count;
_buffer.ReaderCount++;
}
return GetEnumerator_(i);
}
private IEnumerator<T> GetEnumerator_(int i)
{
try
{
while (true)
{
if (_disposed)
throw new ObjectDisposedException("");
var hasValue = default(bool);
var current = default(T);
lock (_source)
{
if (i >= _buffer.Count)
{
if (!_stopped)
{
try
{
hasValue = _source.MoveNext();
if (hasValue)
current = _source.Current;
}
catch (Exception ex)
{
_stopped = true;
_error = ex;
_source.Dispose();
}
}
if (_stopped)
{
if (_error != null)
throw _error;
else
break;
}
if (hasValue)
{
_buffer.Add(current);
}
}
else
{
hasValue = true;
}
}
if (hasValue)
yield return _buffer[i];
else
break;
i++;
}
}
finally
{
if (_buffer != null)
_buffer.Done(i + 1);
}
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
return GetEnumerator();
}
public void Dispose()
{
lock (_source)
{
if (!_disposed)
{
_source.Dispose();
_source = null;
_buffer.Clear();
_buffer = null;
}
_disposed = true;
}
}
}
#endregion
#endregion
#region -- Memoize --
/// <summary>
/// Creates a buffer with a view over the source sequence, causing each enumerator to obtain access to all of the sequence's elements without causing multiple enumerations over the source.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Buffer enabling each enumerator to retrieve all elements from the shared source sequence, without duplicating source enumeration side-effects.</returns>
/// <example>
/// var rng = Enumerable.Range(0, 10).Do(x => Console.WriteLine(x)).Memoize();
///
/// var e1 = rng.GetEnumerator();
///
/// Assert.IsTrue(e1.MoveNext()); // Prints 0
/// Assert.AreEqual(0, e1.Current);
///
/// Assert.IsTrue(e1.MoveNext()); // Prints 1
/// Assert.AreEqual(1, e1.Current);
///
/// var e2 = rng.GetEnumerator();
///
/// Assert.IsTrue(e2.MoveNext()); // Doesn't print anything; the side-effect of Do
/// Assert.AreEqual(0, e2.Current); // has already taken place during e1's iteration.
///
/// Assert.IsTrue(e1.MoveNext()); // Prints 2
/// Assert.AreEqual(2, e1.Current);
/// </example>
public static IBuffer<TSource> Memoize<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return new MemoizedBuffer<TSource>(source.GetEnumerator());
}
/// <summary>
/// Memoizes the source sequence within a selector function where each enumerator can get access to all of the sequence's elements without causing multiple enumerations over the source.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TResult">Result sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">Selector function with memoized access to the source sequence for each enumerator.</param>
/// <returns>Sequence resulting from applying the selector function to the memoized view over the source sequence.</returns>
public static IEnumerable<TResult> Memoize<TSource, TResult>(this IEnumerable<TSource> source, Func<IEnumerable<TSource>, IEnumerable<TResult>> selector)
{
if (source == null)
throw new ArgumentNullException("source");
if (selector == null)
throw new ArgumentNullException("selector");
return Create<TResult>(() => selector(source.Memoize()).GetEnumerator());
}
/// <summary>
/// Creates a buffer with a view over the source sequence, causing a specified number of enumerators to obtain access to all of the sequence's elements without causing multiple enumerations over the source.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="readerCount">Number of enumerators that can access the underlying buffer. Once every enumerator has obtained an element from the buffer, the element is removed from the buffer.</param>
/// <returns>Buffer enabling a specified number of enumerators to retrieve all elements from the shared source sequence, without duplicating source enumeration side-effects.</returns>
public static IBuffer<TSource> Memoize<TSource>(this IEnumerable<TSource> source, int readerCount)
{
if (source == null)
throw new ArgumentNullException("source");
if (readerCount <= 0)
throw new ArgumentOutOfRangeException("readerCount");
return new MemoizedBuffer<TSource>(source.GetEnumerator(), readerCount);
}
/// <summary>
/// Memoizes the source sequence within a selector function where a specified number of enumerators can get access to all of the sequence's elements without causing multiple enumerations over the source.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TResult">Result sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="readerCount">Number of enumerators that can access the underlying buffer. Once every enumerator has obtained an element from the buffer, the element is removed from the buffer.</param>
/// <param name="selector">Selector function with memoized access to the source sequence for a specified number of enumerators.</param>
/// <returns>Sequence resulting from applying the selector function to the memoized view over the source sequence.</returns>
public static IEnumerable<TResult> Memoize<TSource, TResult>(this IEnumerable<TSource> source, int readerCount, Func<IEnumerable<TSource>, IEnumerable<TResult>> selector)
{
if (source == null)
throw new ArgumentNullException("source");
if (readerCount <= 0)
throw new ArgumentOutOfRangeException("readerCount");
if (selector == null)
throw new ArgumentNullException("selector");
return Create<TResult>(() => selector(source.Memoize(readerCount)).GetEnumerator());
}
#region - class MemoizedBuffer -
class MemoizedBuffer<T> : IBuffer<T>
{
private IEnumerator<T> _source;
private IRefCountList<T> _buffer;
private bool _stopped;
private Exception _error;
private bool _disposed;
public MemoizedBuffer(IEnumerator<T> source)
: this(source, new MaxRefCountList<T>())
{
}
public MemoizedBuffer(IEnumerator<T> source, int readerCount)
: this(source, new RefCountList<T>(readerCount))
{
}
private MemoizedBuffer(IEnumerator<T> source, IRefCountList<T> buffer)
{
_source = source;
_buffer = buffer;
}
public IEnumerator<T> GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
return GetEnumerator_();
}
private IEnumerator<T> GetEnumerator_()
{
var i = 0;
try
{
while (true)
{
if (_disposed)
throw new ObjectDisposedException("");
var hasValue = default(bool);
var current = default(T);
lock (_source)
{
if (i >= _buffer.Count)
{
if (!_stopped)
{
try
{
hasValue = _source.MoveNext();
if (hasValue)
current = _source.Current;
}
catch (Exception ex)
{
_stopped = true;
_error = ex;
_source.Dispose();
}
}
if (_stopped)
{
if (_error != null)
throw _error;
else
break;
}
if (hasValue)
{
_buffer.Add(current);
}
}
else
{
hasValue = true;
}
}
if (hasValue)
yield return _buffer[i];
else
break;
i++;
}
}
finally
{
if (_buffer != null)
_buffer.Done(i + 1);
}
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
if (_disposed)
throw new ObjectDisposedException("");
return GetEnumerator();
}
public void Dispose()
{
lock (_source)
{
if (!_disposed)
{
_source.Dispose();
_source = null;
_buffer.Clear();
_buffer = null;
}
_disposed = true;
}
}
}
#endregion
#endregion
}
#region -- interface IBuffer<T> --
/// <summary>
/// Represents a buffer exposing a shared view over an underlying enumerable sequence.
/// </summary>
/// <typeparam name="T">Element type.</typeparam>
public interface IBuffer<T> : IEnumerable<T>, IDisposable
{
}
#endregion
#region -- interface IRefCountList<T> --
interface IRefCountList<T>
{
void Clear();
int Count { get; }
T this[int i]
{
get;
}
void Add(T item);
void Done(int index);
}
#endregion
#region -- class MaxRefCountList<T> --
class MaxRefCountList<T> : IRefCountList<T>
{
private IList<T> _list = new List<T>();
public void Clear()
{
_list.Clear();
}
public int Count
{
get { return _list.Count; }
}
public T this[int i]
{
get { return _list[i]; }
}
public void Add(T item)
{
_list.Add(item);
}
public void Done(int index)
{
}
}
#endregion
#region -- class RefCountList<T> --
class RefCountList<T> : IRefCountList<T>
{
private readonly IDictionary<int, RefCount> _list;
public RefCountList(int readerCount)
{
ReaderCount = readerCount;
_list = new Dictionary<int, RefCount>();
}
public int ReaderCount { get; set; }
public void Clear()
{
_list.Clear();
}
public int Count { get; private set; }
public T this[int i]
{
get
{
Debug.Assert(i < Count);
var res = default(RefCount);
if (!_list.TryGetValue(i, out res))
throw new InvalidOperationException("Element no longer available in the buffer.");
var val = res.Value;
if (--res.Count == 0)
_list.Remove(i);
return val;
}
}
public void Add(T item)
{
_list[Count] = new RefCount { Value = item, Count = ReaderCount };
Count++;
}
public void Done(int index)
{
for (int i = index; i < Count; i++)
{
var ignore = this[i];
}
ReaderCount--;
}
class RefCount
{
public int Count;
public T Value;
}
}
#endregion
}
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