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