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null
else
{
//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
代码语言：javascript复制// == ==
//
// 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 queue
private int _tail; // Last valid element in the queue
private int _size; // Number of elements.
private int _growFactor; // 100 == 1.0, 130 == 1.3, 200 == 2.0
private 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));
else
throw 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
