https://referencesource.microsoft.com/#mscorlib/system/collections/queue.cs

概述

初始化：默认32个，每次2倍扩。所以在初始化时，能预设大小，防止频繁扩容

public Queue()
: this(32, (float)2.0)

入队扩容：内部是个数组，发现size不够，扩容。当头索引在尾索引前，复制size大小到新newarray里；当尾索引在头前，先复制头到数组size-1标，再复制数组0标到尾

private void SetCapacity(int capacity){Object[] newarray = new Object[capacity];if (_size > 0){//如果头在前面if (_head < _tail){Array.Copy(_array, _head, newarray, 0, _size);}//尾在前，头在后，中间是nullelse{//先复制头到数组size-1标Array.Copy(_array, _head, newarray, 0, _array.Length - _head);//再复制数组0标到尾Array.Copy(_array, 0, newarray, _array.Length - _head, _tail);}}_array = newarray;_head = 0;_tail = (_size == capacity) ? 0 : _size; //_size 是指原_array不为空元素的数量_version++;}

入队：容量够，放在数组_tail标处，同时 _tail = (_tail + 1) % _array.Length，可能导致_head > _tail，后面如需扩容时分两步，先先复制头到数组size-1标，再复制数组0标到尾；容量不够，先扩容

 // Adds obj to the tail of the queue.//public virtual void Enqueue(Object obj){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] = obj;_tail = (_tail + 1) % _array.Length;_size++;_version++;}

出队：头标_head复制给新Object，_array[_head] = null;（清除内存），再_head = (_head + 1) % _array.Length;

public virtual Object Dequeue(){if (Count == 0)throw new InvalidOperationException(("InvalidOperation_EmptyQueue"));Contract.EndContractBlock();Object removed = _array[_head];_array[_head] = null;_head = (_head + 1) % _array.Length;_size--;_version++;return removed;}

C#队列全部源码

// ==++==
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--==
/*=============================================================================
**
** Class: Queue
**
** <OWNER>Microsoft</OWNER>
**
** Purpose: A circular-array implementation of a queue.
**
**
=============================================================================*/
namespace System.Collections {using System;using System.Security.Permissions;using System.Diagnostics;using System.Diagnostics.CodeAnalysis;using System.Diagnostics.Contracts;// A simple Queue of objects.  Internally it is implemented as a circular// buffer, so Enqueue can be O(n).  Dequeue is O(1).[DebuggerTypeProxy(typeof(System.Collections.Queue.QueueDebugView))]    [DebuggerDisplay("Count = {Count}")]
[System.Runtime.InteropServices.ComVisible(true)][Serializable]public class Queue : ICollection, ICloneable {private Object[] _array;private int _head;       // First valid element in the queueprivate int _tail;       // Last valid element in the queueprivate int _size;       // Number of elements.private int _growFactor; // 100 == 1.0, 130 == 1.3, 200 == 2.0private int _version;[NonSerialized]private Object _syncRoot;private const int _MinimumGrow = 4;private const int _ShrinkThreshold = 32;// Creates a queue with room for capacity objects. The default initial// capacity and grow factor are used.public Queue() : this(32, (float)2.0) {}// Creates a queue with room for capacity objects. The default grow factor// is used.//public Queue(int capacity) : this(capacity, (float)2.0) {}// Creates a queue with room for capacity objects. When full, the new// capacity is set to the old capacity * growFactor.//public Queue(int capacity, float growFactor) {if (capacity < 0)throw new ArgumentOutOfRangeException("capacity", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));if (!(growFactor >= 1.0 && growFactor <= 10.0))throw new ArgumentOutOfRangeException("growFactor", Environment.GetResourceString("ArgumentOutOfRange_QueueGrowFactor", 1, 10));Contract.EndContractBlock();_array = new Object[capacity];_head = 0;_tail = 0;_size = 0;_growFactor = (int)(growFactor * 100);}// Fills a Queue with the elements of an ICollection.  Uses the enumerator// to get each of the elements.//public Queue(ICollection col) : this((col==null ? 32 : col.Count)){if (col==null)throw new ArgumentNullException("col");Contract.EndContractBlock();IEnumerator en = col.GetEnumerator();while(en.MoveNext())Enqueue(en.Current);}public virtual int Count {get { return _size; }}public virtual Object Clone() {Queue q = new Queue(_size);q._size = _size;int numToCopy = _size;int firstPart = (_array.Length - _head < numToCopy) ? _array.Length - _head : numToCopy;Array.Copy(_array, _head, q._array, 0, firstPart);numToCopy -= firstPart;if (numToCopy > 0)Array.Copy(_array, 0, q._array, _array.Length - _head, numToCopy);q._version = _version;return q;}public virtual bool IsSynchronized {get { return false; }}public virtual Object SyncRoot {get { if( _syncRoot == null) {System.Threading.Interlocked.CompareExchange(ref _syncRoot, new Object(), null);    }return _syncRoot;                 }}// Removes all Objects from the queue.public virtual 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.// public virtual void CopyTo(Array array, int index){if (array==null)throw new ArgumentNullException("array");if (array.Rank != 1)throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported"));if (index < 0)throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));Contract.EndContractBlock();int arrayLen = array.Length;if (arrayLen - index < _size)throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));int numToCopy = _size;if (numToCopy == 0)return;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);}// Adds obj to the tail of the queue.//public virtual void Enqueue(Object obj) {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] = obj;_tail = (_tail + 1) % _array.Length;_size++;_version++;}// GetEnumerator returns an IEnumerator over this Queue.  This// Enumerator will support removing.// public virtual IEnumerator GetEnumerator(){return new QueueEnumerator(this);}// Removes the object at the head of the queue and returns it. If the queue// is empty, this method simply returns null.public virtual Object Dequeue() {if (Count == 0)throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EmptyQueue"));Contract.EndContractBlock();Object removed = _array[_head];_array[_head] = null;_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.public virtual Object Peek() {if (Count == 0)throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EmptyQueue"));Contract.EndContractBlock();return _array[_head];}// Returns a synchronized Queue.  Returns a synchronized wrapper// class around the queue - the caller must not use references to the// original queue.// [HostProtection(Synchronization=true)]public static Queue Synchronized(Queue queue){if (queue==null)throw new ArgumentNullException("queue");Contract.EndContractBlock();return new SynchronizedQueue(queue);}// Returns true if the queue contains at least one object equal to obj.// Equality is determined using obj.Equals().//// Exceptions: ArgumentNullException if obj == null.public virtual bool Contains(Object obj) {int index = _head;int count = _size;while (count-- > 0) {if (obj == null) {if (_array[index] == null)return true;} else if (_array[index] != null && _array[index].Equals(obj)) {return true;}index = (index + 1) % _array.Length;}return false;}internal Object 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.public virtual Object[] ToArray(){Object[] arr = new Object[_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) {Object[] newarray = new Object[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 virtual void TrimToSize(){SetCapacity(_size);}// Implements a synchronization wrapper around a queue.[Serializable]private class SynchronizedQueue : Queue{private Queue _q;private Object root;internal SynchronizedQueue(Queue q) {this._q = q;root = _q.SyncRoot;}public override bool IsSynchronized {get { return true; }}public override Object SyncRoot {get {return root;}}public override int Count { get { lock (root) {return _q.Count;} }}public override void Clear() {lock (root) {_q.Clear();}}public override Object Clone() {lock (root) {return new SynchronizedQueue((Queue)_q.Clone());}}public override bool Contains(Object obj) {lock (root) {return _q.Contains(obj);}}public override void CopyTo(Array array, int arrayIndex) {lock (root) {_q.CopyTo(array, arrayIndex);}}public override void Enqueue(Object value) {lock (root) {_q.Enqueue(value);}}[SuppressMessage("Microsoft.Contracts", "CC1055")]  // Thread safety problems with precondition - can't express the precondition as of Dev10.public override Object Dequeue() {lock (root) {return _q.Dequeue();}}public override IEnumerator GetEnumerator() {lock (root) {return _q.GetEnumerator();}}[SuppressMessage("Microsoft.Contracts", "CC1055")]  // Thread safety problems with precondition - can't express the precondition as of Dev10.public override Object Peek() {lock (root) {return _q.Peek();}}public override Object[] ToArray() {lock (root) {return _q.ToArray();}}public override void TrimToSize() {lock (root) {_q.TrimToSize();}}}   // 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.[Serializable]private class QueueEnumerator : IEnumerator, ICloneable{private Queue _q;private int _index;private int _version;private Object currentElement;internal QueueEnumerator(Queue q) {_q = q;_version = _q._version;_index = 0;currentElement = _q._array;if (_q._size == 0)_index = -1;}public Object Clone(){return MemberwiseClone();}public virtual bool MoveNext() {if (_version != _q._version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion));if (_index < 0) {  currentElement = _q._array;return false;}currentElement = _q.GetElement(_index);_index++;if (_index == _q._size)_index = -1;return true;}public virtual Object Current {get {if (currentElement == _q._array){if (_index == 0)throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));elsethrow new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));}return currentElement;}}public virtual void Reset() {if (_version != _q._version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion));if (_q._size == 0)_index = -1;else_index = 0;currentElement = _q._array;}}internal class QueueDebugView {private Queue queue; public QueueDebugView( Queue queue) {if( queue == null)throw new ArgumentNullException("queue");Contract.EndContractBlock();this.queue = queue;}[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]public Object[] Items   { get {return queue.ToArray();}}}        }
}

源码测试

https://github.com/luoyikun/UnityForTest
MyQueue.cs

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C#：数据结构queue队列源码：循环使用数组头标，尾标，防止不停扩容数组

概述

C#队列全部源码

源码测试

C#：数据结构queue队列源码：循环使用数组头标，尾标，防止不停扩容数组相关推荐

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