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AsyncQueue.cs
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/ Implab / src / Parallels / AsyncQueue.cs
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Added tests for Implab.ServiceHost.Unity configuration loader.
 r289 using System.Threading;
using System.Collections.Generic;
using System;
using System.Collections;
using System.Runtime.CompilerServices;
namespace Implab.Parallels {
public class AsyncQueue<T> : IEnumerable<T> {
class Chunk {
public volatile Chunk next;
volatile int m_low;
volatile int m_hi;
volatile int m_alloc;
readonly int m_size;
readonly T[] m_data;
public Chunk(int size) {
m_size = size;
m_data = new T[size];
}
public Chunk(int size, T value) {
m_size = size;
m_hi = 1;
m_alloc = 1;
m_data = new T[size];
m_data[0] = value;
}
public Chunk(int size, int allocated) {
m_size = size;
m_hi = allocated;
m_alloc = allocated;
m_data = new T[size];
}
public void WriteData(T[] data, int offset, int dest, int length) {
Array.Copy(data, offset, m_data, dest, length);
}
public int Low {
get { return m_low; }
}
public int Hi {
get { return m_hi; }
}
public int Size {
get { return m_size; }
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
void AwaitWrites(int mark) {
if (m_hi != mark) {
SpinWait spin = new SpinWait();
do {
spin.SpinOnce();
} while (m_hi != mark);
}
}
public bool TryEnqueue(T value) {
int alloc;
do {
alloc = m_alloc;
if (alloc >= m_size)
return false;
} while(alloc != Interlocked.CompareExchange(ref m_alloc, alloc + 1, alloc));
m_data[alloc] = value;
AwaitWrites(alloc);
m_hi = alloc + 1;
return true;
}
/// <summary>
/// Prevents from allocating new space in the chunk and waits for all write operations to complete
/// </summary>
public void Seal() {
var actual = Math.Min(Interlocked.Exchange(ref m_alloc, m_size), m_size);
AwaitWrites(actual);
}
public bool TryDequeue(out T value, out bool recycle) {
int low;
do {
low = m_low;
if (low >= m_hi) {
value = default(T);
recycle = (low == m_size);
return false;
}
} while (low != Interlocked.CompareExchange(ref m_low, low + 1, low));
recycle = (low + 1 == m_size);
value = m_data[low];
return true;
}
public bool TryEnqueueBatch(T[] batch, int offset, int length, out int enqueued) {
int alloc;
do {
alloc = m_alloc;
if (alloc >= m_size) {
enqueued = 0;
return false;
} else {
enqueued = Math.Min(length, m_size - alloc);
}
} while (alloc != Interlocked.CompareExchange(ref m_alloc, alloc + enqueued, alloc));
Array.Copy(batch, offset, m_data, alloc, enqueued);
AwaitWrites(alloc);
m_hi = alloc + enqueued;
return true;
}
public bool TryDequeueBatch(T[] buffer, int offset, int length, out int dequeued, out bool recycle) {
int low, hi, batchSize;
do {
low = m_low;
hi = m_hi;
if (low >= hi) {
dequeued = 0;
recycle = (low == m_size);
return false;
}
batchSize = Math.Min(hi - low, length);
} while (low != Interlocked.CompareExchange(ref m_low, low + batchSize, low));
dequeued = batchSize;
recycle = (low + batchSize == m_size);
Array.Copy(m_data, low, buffer, offset, batchSize);
return true;
}
public T GetAt(int pos) {
return m_data[pos];
}
}
public const int DEFAULT_CHUNK_SIZE = 32;
public const int MAX_CHUNK_SIZE = 256;
Chunk m_first;
Chunk m_last;
public AsyncQueue() {
m_first = m_last = new Chunk(DEFAULT_CHUNK_SIZE);
}
/// <summary>
/// Adds the specified value to the queue.
/// </summary>
/// <param name="value">Tha value which will be added to the queue.</param>
public void Enqueue(T value) {
var last = m_last;
SpinWait spin = new SpinWait();
while (!last.TryEnqueue(value)) {
// try to extend queue
var chunk = new Chunk(DEFAULT_CHUNK_SIZE, value);
var t = Interlocked.CompareExchange(ref m_last, chunk, last);
if (t == last) {
last.next = chunk;
break;
} else {
last = t;
}
spin.SpinOnce();
}
}
/// <summary>
/// Adds the specified data to the queue.
/// </summary>
/// <param name="data">The buffer which contains the data to be enqueued.</param>
/// <param name="offset">The offset of the data in the buffer.</param>
/// <param name="length">The size of the data to read from the buffer.</param>
public void EnqueueRange(T[] data, int offset, int length) {
if (data == null)
throw new ArgumentNullException("data");
if (offset < 0)
throw new ArgumentOutOfRangeException("offset");
if (length < 1 || offset + length > data.Length)
throw new ArgumentOutOfRangeException("length");
while (length > 0) {
var last = m_last;
int enqueued;
if (last.TryEnqueueBatch(data, offset, length, out enqueued)) {
length -= enqueued;
offset += enqueued;
}
if (length > 0) {
// we have something to enqueue
var tail = length % MAX_CHUNK_SIZE;
var chunk = new Chunk(Math.Max(tail, DEFAULT_CHUNK_SIZE), tail);
if (last != Interlocked.CompareExchange(ref m_last, chunk, last))
continue; // we wasn't able to catch the writer, roundtrip
// we are lucky
// we can exclusively write our batch, the other writers will continue their work
length -= tail;
for(var i = 0; i < length; i+= MAX_CHUNK_SIZE) {
var node = new Chunk(MAX_CHUNK_SIZE, MAX_CHUNK_SIZE);
node.WriteData(data, offset, 0, MAX_CHUNK_SIZE);
offset += MAX_CHUNK_SIZE;
// fence last.next is volatile
last.next = node;
last = node;
}
if (tail > 0)
chunk.WriteData(data, offset, 0, tail);
// fence last.next is volatile
last.next = chunk;
return;
}
}
}
/// <summary>
/// Tries to retrieve the first element from the queue.
/// </summary>
/// <returns><c>true</c>, if element is dequeued, <c>false</c> otherwise.</returns>
/// <param name="value">The value of the dequeued element.</param>
public bool TryDequeue(out T value) {
var chunk = m_first;
do {
bool recycle;
var result = chunk.TryDequeue(out value, out recycle);
if (recycle && chunk.next != null) {
// this chunk is waste
chunk = Interlocked.CompareExchange(ref m_first, chunk.next, chunk);
} else {
return result; // this chunk is usable and returned actual result
}
if (result) // this chunk is waste but the true result is always actual
return true;
} while (true);
}
/// <summary>
/// Tries to dequeue the specified amount of data from the queue.
/// </summary>
/// <returns><c>true</c>, if data was deuqueued, <c>false</c> otherwise.</returns>
/// <param name="buffer">The buffer to which the data will be written.</param>
/// <param name="offset">The offset in the buffer at which the data will be written.</param>
/// <param name="length">The maximum amount of data to be retrieved.</param>
/// <param name="dequeued">The actual amout of the retrieved data.</param>
public bool TryDequeueRange(T[] buffer, int offset, int length, out int dequeued) {
if (buffer == null)
throw new ArgumentNullException("buffer");
if (offset < 0)
throw new ArgumentOutOfRangeException("offset");
if (length < 1 || offset + length > buffer.Length)
throw new ArgumentOutOfRangeException("length");
var chunk = m_first;
dequeued = 0;
do {
bool recycle;
int actual;
if (chunk.TryDequeueBatch(buffer, offset, length, out actual, out recycle)) {
offset += actual;
length -= actual;
dequeued += actual;
}
if (recycle && chunk.next != null) {
// this chunk is waste
chunk = Interlocked.CompareExchange(ref m_first, chunk.next, chunk);
} else {
chunk = null;
}
if (length == 0)
return true;
} while (chunk != null);
return dequeued != 0;
}
/// <summary>
/// Tries to dequeue all remaining data in the first chunk.
/// </summary>
/// <returns><c>true</c>, if data was dequeued, <c>false</c> otherwise.</returns>
/// <param name="buffer">The buffer to which the data will be written.</param>
/// <param name="offset">The offset in the buffer at which the data will be written.</param>
/// <param name="length">Tha maximum amount of the data to be dequeued.</param>
/// <param name="dequeued">The actual amount of the dequeued data.</param>
public bool TryDequeueChunk(T[] buffer, int offset, int length, out int dequeued) {
if (buffer == null)
throw new ArgumentNullException("buffer");
if (offset < 0)
throw new ArgumentOutOfRangeException("offset");
if (length < 1 || offset + length > buffer.Length)
throw new ArgumentOutOfRangeException("length");
var chunk = m_first;
do {
bool recycle;
chunk.TryDequeueBatch(buffer, offset, length, out dequeued, out recycle);
if (recycle && chunk.next != null) {
// this chunk is waste
chunk = Interlocked.CompareExchange(ref m_first, chunk.next, chunk);
} else {
chunk = null;
}
// if we have dequeued any data, then return
if (dequeued != 0)
return true;
} while (chunk != null);
return false;
}
public void Clear() {
// start the new queue
var chunk = new Chunk(DEFAULT_CHUNK_SIZE);
do {
var first = m_first;
if (first.next == null && first != m_last) {
continue;
}
// here we will create inconsistency which will force others to spin
// and prevent from fetching. chunk.next = null
if (first != Interlocked.CompareExchange(ref m_first, chunk, first))
continue;// inconsistent
m_last = chunk;
return;
} while (true);
}
public List<T> Drain() {
Chunk chunk = null;
do {
var first = m_first;
// first.next is volatile
if (first.next == null) {
if (first != m_last)
continue;
else if (first.Hi == first.Low)
return new List<T>();
}
// start the new queue
if (chunk == null)
chunk = new Chunk(DEFAULT_CHUNK_SIZE);
// here we will create inconsistency which will force others to spin
// and prevent from fetching. chunk.next = null
if (first != Interlocked.CompareExchange(ref m_first, chunk, first))
continue;// inconsistent
var last = Interlocked.Exchange(ref m_last, chunk);
return ReadChunks(first, last);
} while (true);
}
static List<T> ReadChunks(Chunk chunk, object last) {
var result = new List<T>();
var buffer = new T[MAX_CHUNK_SIZE];
int actual;
bool recycle;
SpinWait spin = new SpinWait();
while (chunk != null) {
// ensure all write operations on the chunk are complete
chunk.Seal();
// we need to read the chunk using this way
// since some client still may completing the dequeue
// operation, such clients most likely won't get results
while (chunk.TryDequeueBatch(buffer, 0, buffer.Length, out actual, out recycle))
result.AddRange(new ArraySegmentCollection(buffer, 0, actual));
if (chunk == last) {
chunk = null;
} else {
while (chunk.next == null)
spin.SpinOnce();
chunk = chunk.next;
}
}
return result;
}
struct ArraySegmentCollection : ICollection<T> {
readonly T[] m_data;
readonly int m_offset;
readonly int m_length;
public ArraySegmentCollection(T[] data, int offset, int length) {
m_data = data;
m_offset = offset;
m_length = length;
}
#region ICollection implementation
public void Add(T item) {
throw new NotSupportedException();
}
public void Clear() {
throw new NotSupportedException();
}
public bool Contains(T item) {
return false;
}
public void CopyTo(T[] array, int arrayIndex) {
Array.Copy(m_data, m_offset, array, arrayIndex, m_length);
}
public bool Remove(T item) {
throw new NotSupportedException();
}
public int Count {
get {
return m_length;
}
}
public bool IsReadOnly {
get {
return true;
}
}
#endregion
#region IEnumerable implementation
public IEnumerator<T> GetEnumerator() {
for (int i = m_offset; i < m_length + m_offset; i++)
yield return m_data[i];
}
#endregion
#region IEnumerable implementation
IEnumerator IEnumerable.GetEnumerator() {
return GetEnumerator();
}
#endregion
}
#region IEnumerable implementation
class Enumerator : IEnumerator<T> {
Chunk m_current;
int m_pos = -1;
public Enumerator(Chunk fisrt) {
m_current = fisrt;
}
#region IEnumerator implementation
public bool MoveNext() {
if (m_current == null)
return false;
if (m_pos == -1)
m_pos = m_current.Low;
else
m_pos++;
if (m_pos == m_current.Hi) {
m_current = m_pos == m_current.Size ? m_current.next : null;
m_pos = 0;
if (m_current == null)
return false;
}
return true;
}
public void Reset() {
throw new NotSupportedException();
}
object IEnumerator.Current {
get {
return Current;
}
}
#endregion
#region IDisposable implementation
public void Dispose() {
}
#endregion
#region IEnumerator implementation
public T Current {
get {
if (m_pos == -1 || m_current == null)
throw new InvalidOperationException();
return m_current.GetAt(m_pos);
}
}
#endregion
}
public IEnumerator<T> GetEnumerator() {
return new Enumerator(m_first);
}
#endregion
#region IEnumerable implementation
IEnumerator IEnumerable.GetEnumerator() {
return GetEnumerator();
}
#endregion
}
}