C#ConcurrentDictionary源代码
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Collections;
using System.Runtime.Serialization;
using System.Security;
using System.Security.Permissions;
using System.Collections.ObjectModel;
#if !CDS_COMPILE_JUST_THIS
using System.Diagnostics.Contracts;
#endif
namespace System.Collections.Concurrent
{
/// <summary>
/// Represents a thread-safe collection of keys and values.
/// </summary>
/// <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
/// <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
/// <remarks>
/// All public and protected members of <see cref="ConcurrentDictionary{TKey,TValue}"> are thread-safe and may be used
/// concurrently from multiple threads.
/// </see></remarks>
[Serializable]
[ComVisible(false)]
[DebuggerTypeProxy(typeof(Mscorlib_DictionaryDebugView<,>))]
[DebuggerDisplay("Count = {Count}")]
[HostProtection(Synchronization = true, ExternalThreading = true)]
public class ConcurrentDictionary<tkey, tvalue=""> : IDictionary<tkey, tvalue="">, IDictionary
{
[NonSerialized]
private volatile Node[] m_buckets; // A singly-linked list for each bucket.
[NonSerialized]
private object[] m_locks; // A set of locks, each guarding a section of the table.
[NonSerialized]
private volatile int[] m_countPerLock; // The number of elements guarded by each lock.
private IEqualityComparer<tkey> m_comparer; // Key equality comparer
private KeyValuePair<tkey, tvalue="">[] m_serializationArray; // Used for custom serialization
private int m_serializationConcurrencyLevel; // used to save the concurrency level in serialization
private int m_serializationCapacity; // used to save the capacity in serialization
// The default concurrency level is DEFAULT_CONCURRENCY_MULTIPLIER * #CPUs. The higher the
// DEFAULT_CONCURRENCY_MULTIPLIER, the more concurrent writes can take place without interference
// and blocking, but also the more expensive operations that require all locks become (e.g. table
// resizing, ToArray, Count, etc). According to brief benchmarks that we ran, 4 seems like a good
// compromise.
private const int DEFAULT_CONCURRENCY_MULTIPLIER = 4;
// The default capacity, i.e. the initial # of buckets. When choosing this value, we are making
// a trade-off between the size of a very small dictionary, and the number of resizes when
// constructing a large dictionary. Also, the capacity should not be divisible by a small prime.
private const int DEFAULT_CAPACITY = 31;
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that is empty, has the default concurrency level, has the default initial capacity, and
/// uses the default comparer for the key type.
/// </see></summary>
public ConcurrentDictionary() : this(DefaultConcurrencyLevel, DEFAULT_CAPACITY) { }
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that is empty, has the specified concurrency level and capacity, and uses the default
/// comparer for the key type.
/// </see></summary>
/// <param name="concurrencyLevel">The estimated number of threads that will update the
/// <see cref="ConcurrentDictionary{TKey,TValue}"> concurrently.
/// <param name="capacity">The initial number of elements that the <see cref="ConcurrentDictionary{TKey,TValue}">
/// can contain.
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="concurrencyLevel"> is
/// less than 1.</paramref></exception>
/// <exception cref="T:System.ArgumentOutOfRangeException"> <paramref name="capacity"> is less than
/// 0.</paramref></exception>
public ConcurrentDictionary(int concurrencyLevel, int capacity) : this(concurrencyLevel, capacity, EqualityComparer<tkey>.Default) { }
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that contains elements copied from the specified <see cref="T:System.Collections.IEnumerable{KeyValuePair{TKey,TValue}}">, has the default concurrency
/// level, has the default initial capacity, and uses the default comparer for the key type.
/// </see></see></summary>
/// <param name="collection">The <see cref="T:System.Collections.IEnumerable{KeyValuePair{TKey,TValue}}"> whose elements are copied to
/// the new
/// <see cref="ConcurrentDictionary{TKey,TValue}">.
/// <exception cref="T:System.ArgumentNullException"><paramref name="collection"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentException"><paramref name="collection"> contains one or more
/// duplicate keys.</paramref></exception>
public ConcurrentDictionary(IEnumerable<keyvaluepair<tkey, tvalue="">> collection) : this(collection, EqualityComparer<tkey>.Default) { }
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that is empty, has the specified concurrency level and capacity, and uses the specified
/// <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">.
/// </see></see></summary>
/// <param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">
/// implementation to use when comparing keys.
/// <exception cref="T:System.ArgumentNullException"><paramref name="comparer"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
public ConcurrentDictionary(IEqualityComparer<tkey> comparer) : this(DefaultConcurrencyLevel, DEFAULT_CAPACITY, comparer) { }
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that contains elements copied from the specified <see cref="T:System.Collections.IEnumerable">, has the default concurrency level, has the default
/// initial capacity, and uses the specified
/// <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">.
/// </see></see></see></summary>
/// <param name="collection">The <see cref="T:System.Collections.IEnumerable{KeyValuePair{TKey,TValue}}"> whose elements are copied to
/// the new
/// <see cref="ConcurrentDictionary{TKey,TValue}">.
/// <param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">
/// implementation to use when comparing keys.
/// <exception cref="T:System.ArgumentNullException"><paramref name="collection"> is a null reference
/// (Nothing in Visual Basic). -or-
/// <paramref name="comparer"> is a null reference (Nothing in Visual Basic).
/// </paramref></paramref></exception>
public ConcurrentDictionary(IEnumerable<keyvaluepair<tkey, tvalue="">> collection, IEqualityComparer<tkey> comparer)
: this(DefaultConcurrencyLevel, collection, comparer) { }
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that contains elements copied from the specified <see cref="T:System.Collections.IEnumerable">,
/// has the specified concurrency level, has the specified initial capacity, and uses the specified
/// <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">.
/// </see></see></see></summary>
/// <param name="concurrencyLevel">The estimated number of threads that will update the
/// <see cref="ConcurrentDictionary{TKey,TValue}"> concurrently.
/// <param name="collection">The <see cref="T:System.Collections.IEnumerable{KeyValuePair{TKey,TValue}}"> whose elements are copied to the new
/// <see cref="ConcurrentDictionary{TKey,TValue}">.
/// <param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}"> implementation to use
/// when comparing keys.
/// <exception cref="T:System.ArgumentNullException">
/// <paramref name="collection"> is a null reference (Nothing in Visual Basic).
/// -or-
/// <paramref name="comparer"> is a null reference (Nothing in Visual Basic).
/// </paramref></paramref></exception>
/// <exception cref="T:System.ArgumentOutOfRangeException">
/// <paramref name="concurrencyLevel"> is less than 1.
/// </paramref></exception>
/// <exception cref="T:System.ArgumentException"><paramref name="collection"> contains one or more duplicate keys.</paramref></exception>
public ConcurrentDictionary(
int concurrencyLevel, IEnumerable<keyvaluepair<tkey, tvalue="">> collection, IEqualityComparer<tkey> comparer)
: this(concurrencyLevel, DEFAULT_CAPACITY, comparer)
{
if (collection == null) throw new ArgumentNullException("collection");
if (comparer == null) throw new ArgumentNullException("comparer");
InitializeFromCollection(collection);
}
private void InitializeFromCollection(IEnumerable<keyvaluepair<tkey, tvalue="">> collection)
{
TValue dummy;
foreach (KeyValuePair<tkey, tvalue=""> pair in collection)
{
if (pair.Key == null) throw new ArgumentNullException("key");
if (!TryAddInternal(pair.Key, pair.Value, false, false, out dummy))
{
throw new ArgumentException(GetResource("ConcurrentDictionary_SourceContainsDuplicateKeys"));
}
}
}
/// <summary>
/// Initializes a new instance of the <see cref="ConcurrentDictionary{TKey,TValue}">
/// class that is empty, has the specified concurrency level, has the specified initial capacity, and
/// uses the specified <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">.
/// </see></see></summary>
/// <param name="concurrencyLevel">The estimated number of threads that will update the
/// <see cref="ConcurrentDictionary{TKey,TValue}"> concurrently.
/// <param name="capacity">The initial number of elements that the <see cref="ConcurrentDictionary{TKey,TValue}">
/// can contain.
/// <param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer{TKey}">
/// implementation to use when comparing keys.
/// <exception cref="T:System.ArgumentOutOfRangeException">
/// <paramref name="concurrencyLevel"> is less than 1. -or-
/// <paramref name="capacity"> is less than 0.
/// </paramref></paramref></exception>
/// <exception cref="T:System.ArgumentNullException"><paramref name="comparer"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
public ConcurrentDictionary(int concurrencyLevel, int capacity, IEqualityComparer<tkey> comparer)
{
if (concurrencyLevel < 1)
{
throw new ArgumentOutOfRangeException("concurrencyLevel", GetResource("ConcurrentDictionary_ConcurrencyLevelMustBePositive"));
}
if (capacity < 0)
{
throw new ArgumentOutOfRangeException("capacity", GetResource("ConcurrentDictionary_CapacityMustNotBeNegative"));
}
if (comparer == null) throw new ArgumentNullException("comparer");
// The capacity should be at least as large as the concurrency level. Otherwise, we would have locks that don't guard
// any buckets.
if (capacity < concurrencyLevel)
{
capacity = concurrencyLevel;
}
m_locks = new object[concurrencyLevel];
for (int i = 0; i < m_locks.Length; i++)
{
m_locks[i] = new object();
}
m_countPerLock = new int[m_locks.Length];
m_buckets = new Node[capacity];
m_comparer = comparer;
}
/// <summary>
/// Attempts to add the specified key and value to the <see cref="ConcurrentDictionary{TKey,
/// TValue}">.
/// </see></summary>
/// <param name="key">The key of the element to add.
/// <param name="value">The value of the element to add. The value can be a null reference (Nothing
/// in Visual Basic) for reference types.
/// <returns>true if the key/value pair was added to the <see cref="ConcurrentDictionary{TKey,
/// TValue}">
/// successfully; otherwise, false.</see></returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The <see cref="ConcurrentDictionary{TKey, TValue}">
/// contains too many elements.</see></exception>
public bool TryAdd(TKey key, TValue value)
{
if (key == null) throw new ArgumentNullException("key");
TValue dummy;
return TryAddInternal(key, value, false, true, out dummy);
}
/// <summary>
/// Determines whether the <see cref="ConcurrentDictionary{TKey, TValue}"> contains the specified
/// key.
/// </see></summary>
/// <param name="key">The key to locate in the <see cref="ConcurrentDictionary{TKey,
/// TValue}">.
/// <returns>true if the <see cref="ConcurrentDictionary{TKey, TValue}"> contains an element with
/// the specified key; otherwise, false.</see></returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
public bool ContainsKey(TKey key)
{
if (key == null) throw new ArgumentNullException("key");
TValue throwAwayValue;
return TryGetValue(key, out throwAwayValue);
}
/// <summary>
/// Attempts to remove and return the the value with the specified key from the
/// <see cref="ConcurrentDictionary{TKey, TValue}">.
/// </see></summary>
/// <param name="key">The key of the element to remove and return.
/// <param name="value">When this method returns, <paramref name="value"> contains the object removed from the
/// <see cref="ConcurrentDictionary{TKey,TValue}"> or the default value of <typeparamref name="TValue">
/// if the operation failed.
/// <returns>true if an object was removed successfully; otherwise, false.</returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
public bool TryRemove(TKey key, out TValue value)
{
if (key == null) throw new ArgumentNullException("key");
return TryRemoveInternal(key, out value, false, default(TValue));
}
/// <summary>
/// Removes the specified key from the dictionary if it exists and returns its associated value.
/// If matchValue flag is set, the key will be removed only if is associated with a particular
/// value.
/// </summary>
/// <param name="key">The key to search for and remove if it exists.
/// <param name="value">The variable into which the removed value, if found, is stored.
/// <param name="matchValue">Whether removal of the key is conditional on its value.
/// <param name="oldValue">The conditional value to compare against if <paramref name="matchValue"> is true
/// <returns></returns>
private bool TryRemoveInternal(TKey key, out TValue value, bool matchValue, TValue oldValue)
{
while (true)
{
Node[] buckets = m_buckets;
int bucketNo, lockNo;
GetBucketAndLockNo(m_comparer.GetHashCode(key), out bucketNo, out lockNo, buckets.Length);
lock (m_locks[lockNo])
{
// If the table just got resized, we may not be holding the right lock, and must retry.
// This should be a rare occurence.
if (buckets != m_buckets)
{
continue;
}
Node prev = null;
for (Node curr = m_buckets[bucketNo]; curr != null; curr = curr.m_next)
{
Assert((prev == null && curr == m_buckets[bucketNo]) || prev.m_next == curr);
if (m_comparer.Equals(curr.m_key, key))
{
if (matchValue)
{
bool valuesMatch = EqualityComparer<tvalue>.Default.Equals(oldValue, curr.m_value);
if (!valuesMatch)
{
value = default(TValue);
return false;
}
}
if (prev == null)
{
m_buckets[bucketNo] = curr.m_next;
}
else
{
prev.m_next = curr.m_next;
}
value = curr.m_value;
m_countPerLock[lockNo]--;
return true;
}
prev = curr;
}
}
value = default(TValue);
return false;
}
}
/// <summary>
/// Attempts to get the value associated with the specified key from the <see cref="ConcurrentDictionary{TKey,TValue}">.
/// </see></summary>
/// <param name="key">The key of the value to get.
/// <param name="value">When this method returns, <paramref name="value"> contains the object from
/// the
/// <see cref="ConcurrentDictionary{TKey,TValue}"> with the spedified key or the default value of
/// <typeparamref name="TValue">, if the operation failed.
/// <returns>true if the key was found in the <see cref="ConcurrentDictionary{TKey,TValue}">;
/// otherwise, false.</see></returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
public bool TryGetValue(TKey key, out TValue value)
{
if (key == null) throw new ArgumentNullException("key");
int bucketNo, lockNoUnused;
// We must capture the m_buckets field in a local variable. It is set to a new table on each table resize.
Node[] buckets = m_buckets;
GetBucketAndLockNo(m_comparer.GetHashCode(key), out bucketNo, out lockNoUnused, buckets.Length);
// We can get away w/out a lock here.
Node n = buckets[bucketNo];
// The memory barrier ensures that the load of the fields of 'n' doesn’t move before the load from buckets[i].
Thread.MemoryBarrier();
while (n != null)
{
if (m_comparer.Equals(n.m_key, key))
{
value = n.m_value;
return true;
}
n = n.m_next;
}
value = default(TValue);
return false;
}
/// <summary>
/// Compares the existing value for the specified key with a specified value, and if they’re equal,
/// updates the key with a third value.
/// </summary>
/// <param name="key">The key whose value is compared with <paramref name="comparisonValue"> and
/// possibly replaced.
/// <param name="newValue">The value that replaces the value of the element with <paramref name="key"> if the comparison results in equality.
/// <param name="comparisonValue">The value that is compared to the value of the element with
/// <paramref name="key">.
/// <returns>true if the value with <paramref name="key"> was equal to <paramref name="comparisonValue"> and replaced with <paramref name="newValue">; otherwise,
/// false.</paramref></paramref></paramref></returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null
/// reference.</paramref></exception>
public bool TryUpdate(TKey key, TValue newValue, TValue comparisonValue)
{
if (key == null) throw new ArgumentNullException("key");
int hashcode = m_comparer.GetHashCode(key);
IEqualityComparer<tvalue> valueComparer = EqualityComparer<tvalue>.Default;
while (true)
{
int bucketNo;
int lockNo;
Node[] buckets = m_buckets;
GetBucketAndLockNo(hashcode, out bucketNo, out lockNo, buckets.Length);
lock (m_locks[lockNo])
{
// If the table just got resized, we may not be holding the right lock, and must retry.
// This should be a rare occurence.
if (buckets != m_buckets)
{
continue;
}
// Try to find this key in the bucket
Node prev = null;
for (Node node = buckets[bucketNo]; node != null; node = node.m_next)
{
Assert((prev == null && node == m_buckets[bucketNo]) || prev.m_next == node);
if (m_comparer.Equals(node.m_key, key))
{
if (valueComparer.Equals(node.m_value, comparisonValue))
{
// Replace the old node with a new node. Unfortunately, we cannot simply
// change node.m_value in place. We don't know the size of TValue, so
// its writes may not be atomic.
Node newNode = new Node(node.m_key, newValue, hashcode, node.m_next);
if (prev == null)
{
buckets[bucketNo] = newNode;
}
else
{
prev.m_next = newNode;
}
return true;
}
return false;
}
prev = node;
}
//didn't find the key
return false;
}
}
}
/// <summary>
/// Removes all keys and values from the <see cref="ConcurrentDictionary{TKey,TValue}">.
/// </see></summary>
public void Clear()
{
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
m_buckets = new Node[DEFAULT_CAPACITY];
Array.Clear(m_countPerLock, 0, m_countPerLock.Length);
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Copies the elements of the <see cref="T:System.Collections.Generic.ICollection"> to an array of
/// type <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}">, starting at the
/// specified array index.
/// </see></see></summary>
/// <param name="array">The one-dimensional array of type <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}">
/// that is the destination of the <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"> elements copied from the <see cref="T:System.Collections.ICollection">. The array must have zero-based indexing.
/// <param name="index">The zero-based index in <paramref name="array"> at which copying
/// begins.
/// <exception cref="T:System.ArgumentNullException"><paramref name="array"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"> is less than
/// 0.</paramref></exception>
/// <exception cref="T:System.ArgumentException"><paramref name="index"> is equal to or greater than
/// the length of the <paramref name="array">. -or- The number of elements in the source <see cref="T:System.Collections.ICollection">
/// is greater than the available space from <paramref name="index"> to the end of the destination
/// <paramref name="array">.</paramref></paramref></see></paramref></paramref></exception>
void ICollection<keyvaluepair<tkey, tvalue="">>.CopyTo(KeyValuePair<tkey, tvalue="">[] array, int index)
{
if (array == null) throw new ArgumentNullException("array");
if (index < 0) throw new ArgumentOutOfRangeException("index", GetResource("ConcurrentDictionary_IndexIsNegative"));
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
int count = 0;
for (int i = 0; i < m_locks.Length; i++)
{
count += m_countPerLock[i];
}
if (array.Length - count < index || count < 0) //"count" itself or "count + index" can overflow
{
throw new ArgumentException(GetResource("ConcurrentDictionary_ArrayNotLargeEnough"));
}
CopyToPairs(array, index);
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Copies the key and value pairs stored in the <see cref="ConcurrentDictionary{TKey,TValue}"> to a
/// new array.
/// </see></summary>
/// <returns>A new array containing a snapshot of key and value pairs copied from the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></returns>
public KeyValuePair<tkey, tvalue="">[] ToArray()
{
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
int count = 0;
checked
{
for (int i = 0; i < m_locks.Length; i++)
{
count += m_countPerLock[i];
}
}
KeyValuePair<tkey, tvalue="">[] array = new KeyValuePair<tkey, tvalue="">[count];
CopyToPairs(array, 0);
return array;
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
///
/// Important: the caller must hold all locks in m_locks before calling CopyToPairs.
/// </summary>
private void CopyToPairs(KeyValuePair<tkey, tvalue="">[] array, int index)
{
Node[] buckets = m_buckets;
for (int i = 0; i < buckets.Length; i++)
{
for (Node current = buckets[i]; current != null; current = current.m_next)
{
array[index] = new KeyValuePair<tkey, tvalue="">(current.m_key, current.m_value);
index++; //this should never flow, CopyToPairs is only called when there's no overflow risk
}
}
}
/// <summary>
/// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
///
/// Important: the caller must hold all locks in m_locks before calling CopyToEntries.
/// </summary>
private void CopyToEntries(DictionaryEntry[] array, int index)
{
Node[] buckets = m_buckets;
for (int i = 0; i < buckets.Length; i++)
{
for (Node current = buckets[i]; current != null; current = current.m_next)
{
array[index] = new DictionaryEntry(current.m_key, current.m_value);
index++; //this should never flow, CopyToEntries is only called when there's no overflow risk
}
}
}
/// <summary>
/// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
///
/// Important: the caller must hold all locks in m_locks before calling CopyToObjects.
/// </summary>
private void CopyToObjects(object[] array, int index)
{
Node[] buckets = m_buckets;
for (int i = 0; i < buckets.Length; i++)
{
for (Node current = buckets[i]; current != null; current = current.m_next)
{
array[index] = new KeyValuePair<tkey, tvalue="">(current.m_key, current.m_value);
index++; //this should never flow, CopyToObjects is only called when there's no overflow risk
}
}
}
/// <summary>Returns an enumerator that iterates through the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></summary>
/// <returns>An enumerator for the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></returns>
/// <remarks>
/// The enumerator returned from the dictionary is safe to use concurrently with
/// reads and writes to the dictionary, however it does not represent a moment-in-time snapshot
/// of the dictionary. The contents exposed through the enumerator may contain modifications
/// made to the dictionary after <see cref="GetEnumerator"> was called.
/// </see></remarks>
public IEnumerator<keyvaluepair<tkey, tvalue="">> GetEnumerator()
{
Node[] buckets = m_buckets;
for (int i = 0; i < buckets.Length; i++)
{
Node current = buckets[i];
// The memory barrier ensures that the load of the fields of 'current' doesn’t move before the load from buckets[i].
Thread.MemoryBarrier();
while (current != null)
{
yield return new KeyValuePair<tkey, tvalue="">(current.m_key, current.m_value);
current = current.m_next;
}
}
}
/// <summary>
/// Shared internal implementation for inserts and updates.
/// If key exists, we always return false; and if updateIfExists == true we force update with value;
/// If key doesn't exist, we always add value and return true;
/// </summary>
private bool TryAddInternal(TKey key, TValue value, bool updateIfExists, bool acquireLock, out TValue resultingValue)
{
int hashcode = m_comparer.GetHashCode(key);
while (true)
{
int bucketNo, lockNo;
Node[] buckets = m_buckets;
GetBucketAndLockNo(hashcode, out bucketNo, out lockNo, buckets.Length);
bool resizeDesired = false;
bool lockTaken = false;
try
{
if (acquireLock)
Monitor.Enter(m_locks[lockNo], ref lockTaken);
// If the table just got resized, we may not be holding the right lock, and must retry.
// This should be a rare occurence.
if (buckets != m_buckets)
{
continue;
}
// Try to find this key in the bucket
Node prev = null;
for (Node node = buckets[bucketNo]; node != null; node = node.m_next)
{
Assert((prev == null && node == m_buckets[bucketNo]) || prev.m_next == node);
if (m_comparer.Equals(node.m_key, key))
{
// The key was found in the dictionary. If updates are allowed, update the value for that key.
// We need to create a new node for the update, in order to support TValue types that cannot
// be written atomically, since lock-free reads may be happening concurrently.
if (updateIfExists)
{
Node newNode = new Node(node.m_key, value, hashcode, node.m_next);
if (prev == null)
{
buckets[bucketNo] = newNode;
}
else
{
prev.m_next = newNode;
}
resultingValue = value;
}
else
{
resultingValue = node.m_value;
}
return false;
}
prev = node;
}
// The key was not found in the bucket. Insert the key-value pair.
buckets[bucketNo] = new Node(key, value, hashcode, buckets[bucketNo]);
checked
{
m_countPerLock[lockNo]++;
}
//
// If this lock has element / bucket ratio greater than 1, resize the entire table.
// Note: the formula is chosen to avoid overflow, but has a small inaccuracy due to
// rounding.
//
if (m_countPerLock[lockNo] > buckets.Length / m_locks.Length)
{
resizeDesired = true;
}
}
finally
{
if (lockTaken)
Monitor.Exit(m_locks[lockNo]);
}
//
// The fact that we got here means that we just performed an insertion. If necessary, we will grow the table.
//
// Concurrency notes:
// - Notice that we are not holding any locks at when calling GrowTable. This is necessary to prevent deadlocks.
// - As a result, it is possible that GrowTable will be called unnecessarily. But, GrowTable will obtain lock 0
// and then verify that the table we passed to it as the argument is still the current table.
//
if (resizeDesired)
{
GrowTable(buckets);
}
resultingValue = value;
return true;
}
}
/// <summary>
/// Gets or sets the value associated with the specified key.
/// </summary>
/// <param name="key">The key of the value to get or set.
/// <value>The value associated with the specified key. If the specified key is not found, a get
/// operation throws a
/// <see cref="T:Sytem.Collections.Generic.KeyNotFoundException">, and a set operation creates a new
/// element with the specified key.</see></value>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.Collections.Generic.KeyNotFoundException">The property is retrieved and
/// <paramref name="key">
/// does not exist in the collection.</paramref></exception>
public TValue this[TKey key]
{
get
{
TValue value;
if (!TryGetValue(key, out value))
{
throw new KeyNotFoundException();
}
return value;
}
set
{
if (key == null) throw new ArgumentNullException("key");
TValue dummy;
TryAddInternal(key, value, true, true, out dummy);
}
}
/// <summary>
/// Gets the number of key/value pairs contained in the <see cref="ConcurrentDictionary{TKey,TValue}">.
/// </see></summary>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <value>The number of key/value paris contained in the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></value>
/// <remarks>Count has snapshot semantics and represents the number of items in the <see cref="ConcurrentDictionary{TKey,TValue}">
/// at the moment when Count was accessed.</see></remarks>
public int Count
{
get
{
int count = 0;
int acquiredLocks = 0;
try
{
// Acquire all locks
AcquireAllLocks(ref acquiredLocks);
// Compute the count, we allow overflow
for (int i = 0; i < m_countPerLock.Length; i++)
{
count += m_countPerLock[i];
}
}
finally
{
// Release locks that have been acquired earlier
ReleaseLocks(0, acquiredLocks);
}
return count;
}
}
/// <summary>
/// Adds a key/value pair to the <see cref="ConcurrentDictionary{TKey,TValue}">
/// if the key does not already exist.
/// </see></summary>
/// <param name="key">The key of the element to add.
/// <param name="valueFactory">The function used to generate a value for the key
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentNullException"><paramref name="valueFactory"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <returns>The value for the key. This will be either the existing value for the key if the
/// key is already in the dictionary, or the new value for the key as returned by valueFactory
/// if the key was not in the dictionary.</returns>
public TValue GetOrAdd(TKey key, Func<tkey, tvalue=""> valueFactory)
{
if (key == null) throw new ArgumentNullException("key");
if (valueFactory == null) throw new ArgumentNullException("valueFactory");
TValue resultingValue;
if (TryGetValue(key, out resultingValue))
{
return resultingValue;
}
TryAddInternal(key, valueFactory(key), false, true, out resultingValue);
return resultingValue;
}
/// <summary>
/// Adds a key/value pair to the <see cref="ConcurrentDictionary{TKey,TValue}">
/// if the key does not already exist.
/// </see></summary>
/// <param name="key">The key of the element to add.
/// <param name="value">the value to be added, if the key does not already exist
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <returns>The value for the key. This will be either the existing value for the key if the
/// key is already in the dictionary, or the new value if the key was not in the dictionary.</returns>
public TValue GetOrAdd(TKey key, TValue value)
{
if (key == null) throw new ArgumentNullException("key");
TValue resultingValue;
TryAddInternal(key, value, false, true, out resultingValue);
return resultingValue;
}
/// <summary>
/// Adds a key/value pair to the <see cref="ConcurrentDictionary{TKey,TValue}"> if the key does not already
/// exist, or updates a key/value pair in the <see cref="ConcurrentDictionary{TKey,TValue}"> if the key
/// already exists.
/// </see></see></summary>
/// <param name="key">The key to be added or whose value should be updated
/// <param name="addValueFactory">The function used to generate a value for an absent key
/// <param name="updateValueFactory">The function used to generate a new value for an existing key
/// based on the key's existing value
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentNullException"><paramref name="addValueFactory"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentNullException"><paramref name="updateValueFactory"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <returns>The new value for the key. This will be either be the result of addValueFactory (if the key was
/// absent) or the result of updateValueFactory (if the key was present).</returns>
public TValue AddOrUpdate(TKey key, Func<tkey, tvalue=""> addValueFactory, Func<tkey, tvalue,="" tvalue=""> updateValueFactory)
{
if (key == null) throw new ArgumentNullException("key");
if (addValueFactory == null) throw new ArgumentNullException("addValueFactory");
if (updateValueFactory == null) throw new ArgumentNullException("updateValueFactory");
TValue newValue, resultingValue;
while (true)
{
TValue oldValue;
if (TryGetValue(key, out oldValue))
//key exists, try to update
{
newValue = updateValueFactory(key, oldValue);
if (TryUpdate(key, newValue, oldValue))
{
return newValue;
}
}
else //try add
{
newValue = addValueFactory(key);
if (TryAddInternal(key, newValue, false, true, out resultingValue))
{
return resultingValue;
}
}
}
}
/// <summary>
/// Adds a key/value pair to the <see cref="ConcurrentDictionary{TKey,TValue}"> if the key does not already
/// exist, or updates a key/value pair in the <see cref="ConcurrentDictionary{TKey,TValue}"> if the key
/// already exists.
/// </see></see></summary>
/// <param name="key">The key to be added or whose value should be updated
/// <param name="addValue">The value to be added for an absent key
/// <param name="updateValueFactory">The function used to generate a new value for an existing key based on
/// the key's existing value
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentNullException"><paramref name="updateValueFactory"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <returns>The new value for the key. This will be either be the result of addValueFactory (if the key was
/// absent) or the result of updateValueFactory (if the key was present).</returns>
public TValue AddOrUpdate(TKey key, TValue addValue, Func<tkey, tvalue,="" tvalue=""> updateValueFactory)
{
if (key == null) throw new ArgumentNullException("key");
if (updateValueFactory == null) throw new ArgumentNullException("updateValueFactory");
TValue newValue, resultingValue;
while (true)
{
TValue oldValue;
if (TryGetValue(key, out oldValue))
//key exists, try to update
{
newValue = updateValueFactory(key, oldValue);
if (TryUpdate(key, newValue, oldValue))
{
return newValue;
}
}
else //try add
{
if (TryAddInternal(key, addValue, false, true, out resultingValue))
{
return resultingValue;
}
}
}
}
/// <summary>
/// Gets a value that indicates whether the <see cref="ConcurrentDictionary{TKey,TValue}"> is empty.
/// </see></summary>
/// <value>true if the <see cref="ConcurrentDictionary{TKey,TValue}"> is empty; otherwise,
/// false.</see></value>
public bool IsEmpty
{
get
{
int acquiredLocks = 0;
try
{
// Acquire all locks
AcquireAllLocks(ref acquiredLocks);
for (int i = 0; i < m_countPerLock.Length; i++)
{
if (m_countPerLock[i] != 0)
{
return false;
}
}
}
finally
{
// Release locks that have been acquired earlier
ReleaseLocks(0, acquiredLocks);
}
return true;
}
}
#region IDictionary<tkey,tvalue> members
/// <summary>
/// Adds the specified key and value to the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.
/// </see></summary>
/// <param name="key">The object to use as the key of the element to add.
/// <param name="value">The object to use as the value of the element to add.
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <exception cref="T:System.ArgumentException">
/// An element with the same key already exists in the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></exception>
void IDictionary<tkey, tvalue="">.Add(TKey key, TValue value)
{
if (!TryAdd(key, value))
{
throw new ArgumentException(GetResource("ConcurrentDictionary_KeyAlreadyExisted"));
}
}
/// <summary>
/// Removes the element with the specified key from the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.
/// </see></summary>
/// <param name="key">The key of the element to remove.
/// <returns>true if the element is successfully remove; otherwise false. This method also returns
/// false if
/// <paramref name="key"> was not found in the original <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.
/// </see></paramref></returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
bool IDictionary<tkey, tvalue="">.Remove(TKey key)
{
TValue throwAwayValue;
return TryRemove(key, out throwAwayValue);
}
/// <summary>
/// Gets a collection containing the keys in the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// </see></summary>
/// <value>An <see cref="T:System.Collections.Generic.ICollection{TKey}"> containing the keys in the
/// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.</see></see></value>
public ICollection<tkey> Keys
{
get { return GetKeys(); }
}
/// <summary>
/// Gets a collection containing the values in the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// </see></summary>
/// <value>An <see cref="T:System.Collections.Generic.ICollection{TValue}"> containing the values in
/// the
/// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.</see></see></value>
public ICollection<tvalue> Values
{
get { return GetValues(); }
}
#endregion
#region ICollection<keyvaluepair<tkey,tvalue>> Members
/// <summary>
/// Adds the specified value to the <see cref="T:System.Collections.Generic.ICollection{TValue}">
/// with the specified key.
/// </see></summary>
/// <param name="keyValuePair">The <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}">
/// structure representing the key and value to add to the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// <exception cref="T:System.ArgumentNullException">The <paramref name="keyValuePair"> of <paramref name="keyValuePair"> is null.</paramref></paramref></exception>
/// <exception cref="T:System.OverflowException">The <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">
/// contains too many elements.</see></exception>
/// <exception cref="T:System.ArgumentException">An element with the same key already exists in the
/// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"></see></exception>
void ICollection<keyvaluepair<tkey, tvalue="">>.Add(KeyValuePair<tkey, tvalue=""> keyValuePair)
{
((IDictionary<tkey, tvalue="">)this).Add(keyValuePair.Key, keyValuePair.Value);
}
/// <summary>
/// Determines whether the <see cref="T:System.Collections.Generic.ICollection{TKey,TValue}">
/// contains a specific key and value.
/// </see></summary>
/// <param name="keyValuePair">The <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}">
/// structure to locate in the <see cref="T:System.Collections.Generic.ICollection{TValue}">.
/// <returns>true if the <paramref name="keyValuePair"> is found in the <see cref="T:System.Collections.Generic.ICollection{TKey,TValue}">; otherwise, false.</see></paramref></returns>
bool ICollection<keyvaluepair<tkey, tvalue="">>.Contains(KeyValuePair<tkey, tvalue=""> keyValuePair)
{
TValue value;
if (!TryGetValue(keyValuePair.Key, out value))
{
return false;
}
return EqualityComparer<tvalue>.Default.Equals(value, keyValuePair.Value);
}
/// <summary>
/// Gets a value indicating whether the dictionary is read-only.
/// </summary>
/// <value>true if the <see cref="T:System.Collections.Generic.ICollection{TKey,TValue}"> is
/// read-only; otherwise, false. For <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">, this property always returns
/// false.</see></see></value>
bool ICollection<keyvaluepair<tkey, tvalue="">>.IsReadOnly
{
get { return false; }
}
/// <summary>
/// Removes a key and value from the dictionary.
/// </summary>
/// <param name="keyValuePair">The <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}">
/// structure representing the key and value to remove from the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// <returns>true if the key and value represented by <paramref name="keyValuePair"> is successfully
/// found and removed; otherwise, false.</paramref></returns>
/// <exception cref="T:System.ArgumentNullException">The Key property of <paramref name="keyValuePair"> is a null reference (Nothing in Visual Basic).</paramref></exception>
bool ICollection<keyvaluepair<tkey, tvalue="">>.Remove(KeyValuePair<tkey, tvalue=""> keyValuePair)
{
if (keyValuePair.Key == null) throw new ArgumentNullException(GetResource("ConcurrentDictionary_ItemKeyIsNull"));
TValue throwAwayValue;
return TryRemoveInternal(keyValuePair.Key, out throwAwayValue, true, keyValuePair.Value);
}
#endregion
#region IEnumerable Members
/// <summary>Returns an enumerator that iterates through the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></summary>
/// <returns>An enumerator for the <see cref="ConcurrentDictionary{TKey,TValue}">.</see></returns>
/// <remarks>
/// The enumerator returned from the dictionary is safe to use concurrently with
/// reads and writes to the dictionary, however it does not represent a moment-in-time snapshot
/// of the dictionary. The contents exposed through the enumerator may contain modifications
/// made to the dictionary after <see cref="GetEnumerator"> was called.
/// </see></remarks>
IEnumerator IEnumerable.GetEnumerator()
{
return ((ConcurrentDictionary<tkey, tvalue="">)this).GetEnumerator();
}
#endregion
#region IDictionary Members
/// <summary>
/// Adds the specified key and value to the dictionary.
/// </summary>
/// <param name="key">The object to use as the key.
/// <param name="value">The object to use as the value.
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.OverflowException">The dictionary contains too many
/// elements.</exception>
/// <exception cref="T:System.ArgumentException">
/// <paramref name="key"> is of a type that is not assignable to the key type <typeparamref name="TKey"> of the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">. -or-
/// <paramref name="value"> is of a type that is not assignable to <typeparamref name="TValue">,
/// the type of values in the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// -or- A value with the same key already exists in the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}">.
/// </see></see></typeparamref></paramref></see></typeparamref></paramref></exception>
void IDictionary.Add(object key, object value)
{
if (key == null) throw new ArgumentNullException("key");
if (!(key is TKey)) throw new ArgumentException(GetResource("ConcurrentDictionary_TypeOfKeyIncorrect"));
TValue typedValue;
try
{
typedValue = (TValue)value;
}
catch (InvalidCastException)
{
throw new ArgumentException(GetResource("ConcurrentDictionary_TypeOfValueIncorrect"));
}
((IDictionary<tkey, tvalue="">)this).Add((TKey)key, typedValue);
}
/// <summary>
/// Gets whether the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> contains an
/// element with the specified key.
/// </see></summary>
/// <param name="key">The key to locate in the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.
/// <returns>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> contains
/// an element with the specified key; otherwise, false.</see></returns>
/// <exception cref="T:System.ArgumentNullException"> <paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
bool IDictionary.Contains(object key)
{
if (key == null) throw new ArgumentNullException("key");
return (key is TKey) && ((ConcurrentDictionary<tkey, tvalue="">)this).ContainsKey((TKey)key);
}
/// <summary>Provides an <see cref="T:System.Collections.Generics.IDictionaryEnumerator"> for the
/// <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.</see></see></summary>
/// <returns>An <see cref="T:System.Collections.Generics.IDictionaryEnumerator"> for the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.</see></see></returns>
IDictionaryEnumerator IDictionary.GetEnumerator()
{
return new DictionaryEnumerator(this);
}
/// <summary>
/// Gets a value indicating whether the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> has a fixed size.
/// </see></summary>
/// <value>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> has a
/// fixed size; otherwise, false. For <see cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}">, this property always
/// returns false.</see></see></value>
bool IDictionary.IsFixedSize
{
get { return false; }
}
/// <summary>
/// Gets a value indicating whether the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> is read-only.
/// </see></summary>
/// <value>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"> is
/// read-only; otherwise, false. For <see cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}">, this property always
/// returns false.</see></see></value>
bool IDictionary.IsReadOnly
{
get { return false; }
}
/// <summary>
/// Gets an <see cref="T:System.Collections.ICollection"> containing the keys of the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.
/// </see></see></summary>
/// <value>An <see cref="T:System.Collections.ICollection"> containing the keys of the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}">.</see></see></value>
ICollection IDictionary.Keys
{
get { return GetKeys(); }
}
/// <summary>
/// Removes the element with the specified key from the <see cref="T:System.Collections.IDictionary">.
/// </see></summary>
/// <param name="key">The key of the element to remove.
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
void IDictionary.Remove(object key)
{
if (key == null) throw new ArgumentNullException("key");
TValue throwAwayValue;
if (key is TKey)
{
this.TryRemove((TKey)key, out throwAwayValue);
}
}
/// <summary>
/// Gets an <see cref="T:System.Collections.ICollection"> containing the values in the <see cref="T:System.Collections.IDictionary">.
/// </see></see></summary>
/// <value>An <see cref="T:System.Collections.ICollection"> containing the values in the <see cref="T:System.Collections.IDictionary">.</see></see></value>
ICollection IDictionary.Values
{
get { return GetValues(); }
}
/// <summary>
/// Gets or sets the value associated with the specified key.
/// </summary>
/// <param name="key">The key of the value to get or set.
/// <value>The value associated with the specified key, or a null reference (Nothing in Visual Basic)
/// if <paramref name="key"> is not in the dictionary or <paramref name="key"> is of a type that is
/// not assignable to the key type <typeparamref name="TKey"> of the <see cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}">.</see></typeparamref></paramref></paramref></value>
/// <exception cref="T:System.ArgumentNullException"><paramref name="key"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentException">
/// A value is being assigned, and <paramref name="key"> is of a type that is not assignable to the
/// key type <typeparamref name="TKey"> of the <see cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}">. -or- A value is being
/// assigned, and <paramref name="key"> is of a type that is not assignable to the value type
/// <typeparamref name="TValue"> of the <see cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}">
/// </see></typeparamref></paramref></see></typeparamref></paramref></exception>
object IDictionary.this[object key]
{
get
{
if (key == null) throw new ArgumentNullException("key");
TValue value;
if (key is TKey && this.TryGetValue((TKey)key, out value))
{
return value;
}
return null;
}
set
{
if (key == null) throw new ArgumentNullException("key");
if (!(key is TKey)) throw new ArgumentException(GetResource("ConcurrentDictionary_TypeOfKeyIncorrect"));
if (!(value is TValue)) throw new ArgumentException(GetResource("ConcurrentDictionary_TypeOfValueIncorrect"));
((ConcurrentDictionary<tkey, tvalue="">)this)[(TKey)key] = (TValue)value;
}
}
#endregion
#region ICollection Members
/// <summary>
/// Copies the elements of the <see cref="T:System.Collections.ICollection"> to an array, starting
/// at the specified array index.
/// </see></summary>
/// <param name="array">The one-dimensional array that is the destination of the elements copied from
/// the <see cref="T:System.Collections.ICollection">. The array must have zero-based
/// indexing.
/// <param name="index">The zero-based index in <paramref name="array"> at which copying
/// begins.
/// <exception cref="T:System.ArgumentNullException"><paramref name="array"> is a null reference
/// (Nothing in Visual Basic).</paramref></exception>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"> is less than
/// 0.</paramref></exception>
/// <exception cref="T:System.ArgumentException"><paramref name="index"> is equal to or greater than
/// the length of the <paramref name="array">. -or- The number of elements in the source <see cref="T:System.Collections.ICollection">
/// is greater than the available space from <paramref name="index"> to the end of the destination
/// <paramref name="array">.</paramref></paramref></see></paramref></paramref></exception>
void ICollection.CopyTo(Array array, int index)
{
if (array == null) throw new ArgumentNullException("array");
if (index < 0) throw new ArgumentOutOfRangeException("index", GetResource("ConcurrentDictionary_IndexIsNegative"));
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
int count = 0;
for (int i = 0; i < m_locks.Length; i++)
{
count += m_countPerLock[i];
}
if (array.Length - count < index || count < 0) //"count" itself or "count + index" can overflow
{
throw new ArgumentException(GetResource("ConcurrentDictionary_ArrayNotLargeEnough"));
}
// To be consistent with the behavior of ICollection.CopyTo() in Dictionary<tkey,tvalue>,
// we recognize three types of target arrays:
// - an array of KeyValuePair<tkey, tvalue=""> structs
// - an array of DictionaryEntry structs
// - an array of objects
KeyValuePair<tkey, tvalue="">[] pairs = array as KeyValuePair<tkey, tvalue="">[];
if (pairs != null)
{
CopyToPairs(pairs, index);
return;
}
DictionaryEntry[] entries = array as DictionaryEntry[];
if (entries != null)
{
CopyToEntries(entries, index);
return;
}
object[] objects = array as object[];
if (objects != null)
{
CopyToObjects(objects, index);
return;
}
throw new ArgumentException(GetResource("ConcurrentDictionary_ArrayIncorrectType"), "array");
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Gets a value indicating whether access to the <see cref="T:System.Collections.ICollection"> is
/// synchronized with the SyncRoot.
/// </see></summary>
/// <value>true if access to the <see cref="T:System.Collections.ICollection"> is synchronized
/// (thread safe); otherwise, false. For <see cref="T:System.Collections.Concurrent.ConcurrentDictionary{TKey,TValue}">, this property always
/// returns false.</see></see></value>
bool ICollection.IsSynchronized
{
get { return false; }
}
/// <summary>
/// Gets an object that can be used to synchronize access to the <see cref="T:System.Collections.ICollection">. This property is not supported.
/// </see></summary>
/// <exception cref="T:System.NotSupportedException">The SyncRoot property is not supported.</exception>
object ICollection.SyncRoot
{
get
{
throw new NotSupportedException(Environment.GetResourceString("ConcurrentCollection_SyncRoot_NotSupported"));
}
}
#endregion
/// <summary>
/// Replaces the internal table with a larger one. To prevent multiple threads from resizing the
/// table as a result of ----s, the table of buckets that was deemed too small is passed in as
/// an argument to GrowTable(). GrowTable() obtains a lock, and then checks whether the bucket
/// table has been replaced in the meantime or not.
/// </summary>
/// <param name="buckets">Reference to the bucket table that was deemed too small.
private void GrowTable(Node[] buckets)
{
int locksAcquired = 0;
try
{
// The thread that first obtains m_locks[0] will be the one doing the resize operation
AcquireLocks(0, 1, ref locksAcquired);
// Make sure nobody resized the table while we were waiting for lock 0:
if (buckets != m_buckets)
{
// We assume that since the table reference is different, it was already resized. If we ever
// decide to do table shrinking, or replace the table for other reasons, we will have to revisit
// this logic.
return;
}
// Compute the new table size. We find the smallest integer larger than twice the previous table size, and not divisible by
// 2,3,5 or 7. We can consider a different table-sizing policy in the future.
int newLength;
try
{
checked
{
// Double the size of the buckets table and add one, so that we have an odd integer.
newLength = buckets.Length * 2 + 1;
// Now, we only need to check odd integers, and find the first that is not divisible
// by 3, 5 or 7.
while (newLength % 3 == 0 || newLength % 5 == 0 || newLength % 7 == 0)
{
newLength += 2;
}
Assert(newLength % 2 != 0);
}
}
catch (OverflowException)
{
// If we were to resize the table, its new size will not fit into a 32-bit signed int. Just return.
return;
}
Node[] newBuckets = new Node[newLength];
int[] newCountPerLock = new int[m_locks.Length];
// Now acquire all other locks for the table
AcquireLocks(1, m_locks.Length, ref locksAcquired);
// Copy all data into a new table, creating new nodes for all elements
for (int i = 0; i < buckets.Length; i++)
{
Node current = buckets[i];
while (current != null)
{
Node next = current.m_next;
int newBucketNo, newLockNo;
GetBucketAndLockNo(current.m_hashcode, out newBucketNo, out newLockNo, newBuckets.Length);
newBuckets[newBucketNo] = new Node(current.m_key, current.m_value, current.m_hashcode, newBuckets[newBucketNo]);
checked
{
newCountPerLock[newLockNo]++;
}
current = next;
}
}
// And finally adjust m_buckets and m_countPerLock to point to data for the new table
m_buckets = newBuckets;
m_countPerLock = newCountPerLock;
}
finally
{
// Release all locks that we took earlier
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Computes the bucket and lock number for a particular key.
/// </summary>
private void GetBucketAndLockNo(
int hashcode, out int bucketNo, out int lockNo, int bucketCount)
{
bucketNo = (hashcode & 0x7fffffff) % bucketCount;
lockNo = bucketNo % m_locks.Length;
Assert(bucketNo >= 0 && bucketNo < bucketCount);
Assert(lockNo >= 0 && lockNo < m_locks.Length);
}
/// <summary>
/// The number of concurrent writes for which to optimize by default.
/// </summary>
private static int DefaultConcurrencyLevel
{
get { return DEFAULT_CONCURRENCY_MULTIPLIER * Environment.ProcessorCount; }
}
/// <summary>
/// Acquires all locks for this hash table, and increments locksAcquired by the number
/// of locks that were successfully acquired. The locks are acquired in an increasing
/// order.
/// </summary>
private void AcquireAllLocks(ref int locksAcquired)
{
#if !FEATURE_PAL
if (CDSCollectionETWBCLProvider.Log.IsEnabled())
{
CDSCollectionETWBCLProvider.Log.ConcurrentDictionary_AcquiringAllLocks(m_buckets.Length);
}
#endif //!FEATURE_PAL
AcquireLocks(0, m_locks.Length, ref locksAcquired);
Assert(locksAcquired == m_locks.Length);
}
/// <summary>
/// Acquires a contiguous range of locks for this hash table, and increments locksAcquired
/// by the number of locks that were successfully acquired. The locks are acquired in an
/// increasing order.
/// </summary>
private void AcquireLocks(int fromInclusive, int toExclusive, ref int locksAcquired)
{
Assert(fromInclusive <= toExclusive);
for (int i = fromInclusive; i < toExclusive; i++)
{
bool lockTaken = false;
try
{
#if CDS_COMPILE_JUST_THIS
Monitor.Enter(m_locks[i]);
lockTaken = true;
#else
Monitor.Enter(m_locks[i], ref lockTaken);
#endif
}
finally
{
if (lockTaken)
{
locksAcquired++;
}
}
}
}
/// <summary>
/// Releases a contiguous range of locks.
/// </summary>
private void ReleaseLocks(int fromInclusive, int toExclusive)
{
Assert(fromInclusive <= toExclusive);
for (int i = fromInclusive; i < toExclusive; i++)
{
Monitor.Exit(m_locks[i]);
}
}
/// <summary>
/// Gets a collection containing the keys in the dictionary.
/// </summary>
private ReadOnlyCollection<tkey> GetKeys()
{
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
List<tkey> keys = new List<tkey>();
for (int i = 0; i < m_buckets.Length; i++)
{
Node current = m_buckets[i];
while (current != null)
{
keys.Add(current.m_key);
current = current.m_next;
}
}
return new ReadOnlyCollection<tkey>(keys);
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// Gets a collection containing the values in the dictionary.
/// </summary>
private ReadOnlyCollection<tvalue> GetValues()
{
int locksAcquired = 0;
try
{
AcquireAllLocks(ref locksAcquired);
List<tvalue> values = new List<tvalue>();
for (int i = 0; i < m_buckets.Length; i++)
{
Node current = m_buckets[i];
while (current != null)
{
values.Add(current.m_value);
current = current.m_next;
}
}
return new ReadOnlyCollection<tvalue>(values);
}
finally
{
ReleaseLocks(0, locksAcquired);
}
}
/// <summary>
/// A helper method for asserts.
/// </summary>
[Conditional("DEBUG")]
private void Assert(bool condition)
{
#if CDS_COMPILE_JUST_THIS
if (!condition)
{
throw new Exception("Assertion failed.");
}
#else
Contract.Assert(condition);
#endif
}
/// <summary>
/// A helper function to obtain the string for a particular resource key.
/// </summary>
/// <param name="key">
/// <returns></returns>
private string GetResource(string key)
{
Assert(key != null);
#if CDS_COMPILE_JUST_THIS
return key;
#else
return Environment.GetResourceString(key);
#endif
}
/// <summary>
/// A node in a singly-linked list representing a particular hash table bucket.
/// </summary>
private class Node
{
internal TKey m_key;
internal TValue m_value;
internal volatile Node m_next;
internal int m_hashcode;
internal Node(TKey key, TValue value, int hashcode)
: this(key, value, hashcode, null)
{
}
internal Node(TKey key, TValue value, int hashcode, Node next)
{
m_key = key;
m_value = value;
m_next = next;
m_hashcode = hashcode;
}
}
/// <summary>
/// A private class to represent enumeration over the dictionary that implements the
/// IDictionaryEnumerator interface.
/// </summary>
private class DictionaryEnumerator : IDictionaryEnumerator
{
IEnumerator<keyvaluepair<tkey, tvalue="">> m_enumerator; // Enumerator over the dictionary.
internal DictionaryEnumerator(ConcurrentDictionary<tkey, tvalue=""> dictionary)
{
m_enumerator = dictionary.GetEnumerator();
}
public DictionaryEntry Entry
{
get { return new DictionaryEntry(m_enumerator.Current.Key, m_enumerator.Current.Value); }
}
public object Key
{
get { return m_enumerator.Current.Key; }
}
public object Value
{
get { return m_enumerator.Current.Value; }
}
public object Current
{
get { return this.Entry; }
}
public bool MoveNext()
{
return m_enumerator.MoveNext();
}
public void Reset()
{
m_enumerator.Reset();
}
}
/// <summary>
/// Get the data array to be serialized
/// </summary>
[OnSerializing]
private void OnSerializing(StreamingContext context)
{
// save the data into the serialization array to be saved
m_serializationArray = ToArray();
m_serializationConcurrencyLevel = m_locks.Length;
m_serializationCapacity = m_buckets.Length;
}
/// <summary>
/// Construct the dictionary from a previously seiralized one
/// </summary>
[OnDeserialized]
private void OnDeserialized(StreamingContext context)
{
KeyValuePair<tkey, tvalue="">[] array = m_serializationArray;
m_buckets = new Node[m_serializationCapacity];
m_countPerLock = new int[m_serializationConcurrencyLevel];
m_locks = new object[m_serializationConcurrencyLevel];
for (int i = 0; i < m_locks.Length; i++)
{
m_locks[i] = new object();
}
InitializeFromCollection(array);
m_serializationArray = null;
}
}
}
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