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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*=============================================================================
**
** Class: Queue
**
** Purpose: A circular-array implementation of a generic queue.
**
** Date: January 28, 2003
**
=============================================================================*/
namespace System.Collections.Generic {
using System;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Security.Permissions;
// A simple Queue of generic objects. Internally it is implemented as a
// circular buffer, so Enqueue can be O(n). Dequeue is O(1).
[DebuggerTypeProxy(typeof(System_QueueDebugView<>))]
[DebuggerDisplay("Count = {Count}")]
#if !SILVERLIGHT
[Serializable()]
#endif
[System.Runtime.InteropServices.ComVisible(false)]
public class Queue<T> : IEnumerable<T>,
System.Collections.ICollection,
IReadOnlyCollection<T> {
private T[] _array;
private int _head; // First valid element in the queue
private int _tail; // Last valid element in the queue
private int _size; // Number of elements.
private int _version;
#if !SILVERLIGHT
[NonSerialized]
#endif
private Object _syncRoot;
private const int _MinimumGrow = 4;
private const int _ShrinkThreshold = 32;
private const int _GrowFactor = 200; // double each time
private const int _DefaultCapacity = 4;
static T[] _emptyArray = new T[0];
// Creates a queue with room for capacity objects. The default initial
// capacity and grow factor are used.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Queue"]/*' />
public Queue() {
_array = _emptyArray;
}
// Creates a queue with room for capacity objects. The default grow factor
// is used.
//
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Queue1"]/*' />
public Queue(int capacity) {
if (capacity < 0)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity, ExceptionResource.ArgumentOutOfRange_NeedNonNegNumRequired);
_array = new T[capacity];
_head = 0;
_tail = 0;
_size = 0;
}
// Fills a Queue with the elements of an ICollection. Uses the enumerator
// to get each of the elements.
//
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Queue3"]/*' />
public Queue(IEnumerable<T> collection)
{
if (collection == null)
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
_array = new T[_DefaultCapacity];
_size = 0;
_version = 0;
using(IEnumerator<T> en = collection.GetEnumerator()) {
while(en.MoveNext()) {
Enqueue(en.Current);
}
}
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Count"]/*' />
public int Count {
get { return _size; }
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.IsSynchronized"]/*' />
bool System.Collections.ICollection.IsSynchronized {
get { return false; }
}
Object System.Collections.ICollection.SyncRoot {
get {
if( _syncRoot == null) {
System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);
}
return _syncRoot;
}
}
// Removes all Objects from the queue.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Clear"]/*' />
public void Clear() {
if (_head < _tail)
Array.Clear(_array, _head, _size);
else {
Array.Clear(_array, _head, _array.Length - _head);
Array.Clear(_array, 0, _tail);
}
_head = 0;
_tail = 0;
_size = 0;
_version++;
}
// CopyTo copies a collection into an Array, starting at a particular
// index into the array.
//
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.CopyTo"]/*' />
public void CopyTo(T[] array, int arrayIndex)
{
if (array==null) {
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
}
if (arrayIndex < 0 || arrayIndex > array.Length) {
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.arrayIndex, ExceptionResource.ArgumentOutOfRange_Index);
}
int arrayLen = array.Length;
if (arrayLen - arrayIndex < _size) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
}
int numToCopy = (arrayLen - arrayIndex < _size) ? (arrayLen - arrayIndex) : _size;
if (numToCopy == 0) return;
int firstPart = (_array.Length - _head < numToCopy) ? _array.Length - _head : numToCopy;
Array.Copy(_array, _head, array, arrayIndex, firstPart);
numToCopy -= firstPart;
if (numToCopy > 0) {
Array.Copy(_array, 0, array, arrayIndex+_array.Length - _head, numToCopy);
}
}
void System.Collections.ICollection.CopyTo(Array array, int index)
{
if (array == null) {
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
}
if (array.Rank != 1) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
}
if( array.GetLowerBound(0) != 0 ) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
}
int arrayLen = array.Length;
if (index < 0 || index > arrayLen) {
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index);
}
if (arrayLen - index < _size) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
}
int numToCopy = (arrayLen-index < _size) ? arrayLen-index : _size;
if (numToCopy == 0) return;
try {
int firstPart = (_array.Length - _head < numToCopy) ? _array.Length - _head : numToCopy;
Array.Copy(_array, _head, array, index, firstPart);
numToCopy -= firstPart;
if (numToCopy > 0) {
Array.Copy(_array, 0, array, index+_array.Length - _head, numToCopy);
}
}
catch(ArrayTypeMismatchException) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType);
}
}
// Adds item to the tail of the queue.
//
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Enqueue"]/*' />
public void Enqueue(T item) {
if (_size == _array.Length) {
int newcapacity = (int)((long)_array.Length * (long)_GrowFactor / 100);
if (newcapacity < _array.Length + _MinimumGrow) {
newcapacity = _array.Length + _MinimumGrow;
}
SetCapacity(newcapacity);
}
_array[_tail] = item;
_tail = (_tail + 1) % _array.Length;
_size++;
_version++;
}
// GetEnumerator returns an IEnumerator over this Queue. This
// Enumerator will support removing.
//
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.GetEnumerator"]/*' />
public Enumerator GetEnumerator()
{
return new Enumerator(this);
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.IEnumerable.GetEnumerator"]/*' />
/// <internalonly/>
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
return new Enumerator(this);
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return new Enumerator(this);
}
// Removes the object at the head of the queue and returns it. If the queue
// is empty, this method simply returns null.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Dequeue"]/*' />
public T Dequeue() {
if (_size == 0)
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EmptyQueue);
T removed = _array[_head];
_array[_head] = default(T);
_head = (_head + 1) % _array.Length;
_size--;
_version++;
return removed;
}
// Returns the object at the head of the queue. The object remains in the
// queue. If the queue is empty, this method throws an
// InvalidOperationException.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Peek"]/*' />
public T Peek() {
if (_size == 0)
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EmptyQueue);
return _array[_head];
}
// Returns true if the queue contains at least one object equal to item.
// Equality is determined using item.Equals().
//
// Exceptions: ArgumentNullException if item == null.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.Contains"]/*' />
public bool Contains(T item) {
int index = _head;
int count = _size;
EqualityComparer<T> c = EqualityComparer<T>.Default;
while (count-- > 0) {
if (((Object) item) == null) {
if (((Object) _array[index]) == null)
return true;
}
else if (_array[index] != null && c.Equals(_array[index], item)) {
return true;
}
index = (index + 1) % _array.Length;
}
return false;
}
internal T GetElement(int i)
{
return _array[(_head + i) % _array.Length];
}
// Iterates over the objects in the queue, returning an array of the
// objects in the Queue, or an empty array if the queue is empty.
// The order of elements in the array is first in to last in, the same
// order produced by successive calls to Dequeue.
/// <include file='doc\Queue.uex' path='docs/doc[@for="Queue.ToArray"]/*' />
public T[] ToArray()
{
T[] arr = new T[_size];
if (_size==0)
return arr;
if (_head < _tail) {
Array.Copy(_array, _head, arr, 0, _size);
} else {
Array.Copy(_array, _head, arr, 0, _array.Length - _head);
Array.Copy(_array, 0, arr, _array.Length - _head, _tail);
}
return arr;
}
// PRIVATE Grows or shrinks the buffer to hold capacity objects. Capacity
// must be >= _size.
private void SetCapacity(int capacity) {
T[] newarray = new T[capacity];
if (_size > 0) {
if (_head < _tail) {
Array.Copy(_array, _head, newarray, 0, _size);
} else {
Array.Copy(_array, _head, newarray, 0, _array.Length - _head);
Array.Copy(_array, 0, newarray, _array.Length - _head, _tail);
}
}
_array = newarray;
_head = 0;
_tail = (_size == capacity) ? 0 : _size;
_version++;
}
public void TrimExcess() {
int threshold = (int)(((double)_array.Length) * 0.9);
if( _size < threshold ) {
SetCapacity(_size);
}
}
// Implements an enumerator for a Queue. The enumerator uses the
// internal version number of the list to ensure that no modifications are
// made to the list while an enumeration is in progress.
/// <include file='doc\Queue.uex' path='docs/doc[@for="QueueEnumerator"]/*' />
#if !SILVERLIGHT
[Serializable()]
#endif
[SuppressMessage("Microsoft.Performance", "CA1815:OverrideEqualsAndOperatorEqualsOnValueTypes", Justification = "not an expected scenario")]
public struct Enumerator : IEnumerator<T>,
System.Collections.IEnumerator
{
private Queue<T> _q;
private int _index; // -1 = not started, -2 = ended/disposed
private int _version;
private T _currentElement;
internal Enumerator(Queue<T> q) {
_q = q;
_version = _q._version;
_index = -1;
_currentElement = default(T);
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="QueueEnumerator.Dispose"]/*' />
public void Dispose()
{
_index = -2;
_currentElement = default(T);
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="QueueEnumerator.MoveNext"]/*' />
public bool MoveNext() {
if (_version != _q._version) ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
if (_index == -2)
return false;
_index++;
if (_index == _q._size) {
_index = -2;
_currentElement = default(T);
return false;
}
_currentElement = _q.GetElement(_index);
return true;
}
/// <include file='doc\Queue.uex' path='docs/doc[@for="QueueEnumerator.Current"]/*' />
public T Current {
get {
if (_index < 0)
{
if (_index == -1)
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumNotStarted);
else
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumEnded);
}
return _currentElement;
}
}
Object System.Collections.IEnumerator.Current {
get {
if (_index < 0)
{
if (_index == -1)
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumNotStarted);
else
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumEnded);
}
return _currentElement;
}
}
void System.Collections.IEnumerator.Reset() {
if (_version != _q._version) ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
_index = -1;
_currentElement = default(T);
}
}
}
}
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