diff options
Diffstat (limited to 'src/mscorlib/src/System/Threading/AsyncLocal.cs')
| -rw-r--r-- | src/mscorlib/src/System/Threading/AsyncLocal.cs | 487 |
1 files changed, 0 insertions, 487 deletions
diff --git a/src/mscorlib/src/System/Threading/AsyncLocal.cs b/src/mscorlib/src/System/Threading/AsyncLocal.cs deleted file mode 100644 index 8c4319bd2c..0000000000 --- a/src/mscorlib/src/System/Threading/AsyncLocal.cs +++ /dev/null @@ -1,487 +0,0 @@ -// Licensed to the .NET Foundation under one or more agreements. -// The .NET Foundation licenses this file to you under the MIT license. -// See the LICENSE file in the project root for more information. - -using System; -using System.Collections.Generic; -using System.Diagnostics; -using System.Diagnostics.Contracts; -using System.Security; - -namespace System.Threading -{ - // - // AsyncLocal<T> represents "ambient" data that is local to a given asynchronous control flow, such as an - // async method. For example, say you want to associate a culture with a given async flow: - // - // static AsyncLocal<Culture> s_currentCulture = new AsyncLocal<Culture>(); - // - // static async Task SomeOperationAsync(Culture culture) - // { - // s_currentCulture.Value = culture; - // - // await FooAsync(); - // } - // - // static async Task FooAsync() - // { - // PrintStringWithCulture(s_currentCulture.Value); - // } - // - // AsyncLocal<T> also provides optional notifications when the value associated with the current thread - // changes, either because it was explicitly changed by setting the Value property, or implicitly changed - // when the thread encountered an "await" or other context transition. For example, we might want our - // current culture to be communicated to the OS as well: - // - // static AsyncLocal<Culture> s_currentCulture = new AsyncLocal<Culture>( - // args => - // { - // NativeMethods.SetThreadCulture(args.CurrentValue.LCID); - // }); - // - public sealed class AsyncLocal<T> : IAsyncLocal - { - private readonly Action<AsyncLocalValueChangedArgs<T>> m_valueChangedHandler; - - // - // Constructs an AsyncLocal<T> that does not receive change notifications. - // - public AsyncLocal() - { - } - - // - // Constructs an AsyncLocal<T> with a delegate that is called whenever the current value changes - // on any thread. - // - public AsyncLocal(Action<AsyncLocalValueChangedArgs<T>> valueChangedHandler) - { - m_valueChangedHandler = valueChangedHandler; - } - - public T Value - { - get - { - object obj = ExecutionContext.GetLocalValue(this); - return (obj == null) ? default(T) : (T)obj; - } - set - { - ExecutionContext.SetLocalValue(this, value, m_valueChangedHandler != null); - } - } - - void IAsyncLocal.OnValueChanged(object previousValueObj, object currentValueObj, bool contextChanged) - { - Debug.Assert(m_valueChangedHandler != null); - T previousValue = previousValueObj == null ? default(T) : (T)previousValueObj; - T currentValue = currentValueObj == null ? default(T) : (T)currentValueObj; - m_valueChangedHandler(new AsyncLocalValueChangedArgs<T>(previousValue, currentValue, contextChanged)); - } - } - - // - // Interface to allow non-generic code in ExecutionContext to call into the generic AsyncLocal<T> type. - // - internal interface IAsyncLocal - { - void OnValueChanged(object previousValue, object currentValue, bool contextChanged); - } - - public struct AsyncLocalValueChangedArgs<T> - { - public T PreviousValue { get; private set; } - public T CurrentValue { get; private set; } - - // - // If the value changed because we changed to a different ExecutionContext, this is true. If it changed - // because someone set the Value property, this is false. - // - public bool ThreadContextChanged { get; private set; } - - internal AsyncLocalValueChangedArgs(T previousValue, T currentValue, bool contextChanged) - : this() - { - PreviousValue = previousValue; - CurrentValue = currentValue; - ThreadContextChanged = contextChanged; - } - } - - // - // Interface used to store an IAsyncLocal => object mapping in ExecutionContext. - // Implementations are specialized based on the number of elements in the immutable - // map in order to minimize memory consumption and look-up times. - // - interface IAsyncLocalValueMap - { - bool TryGetValue(IAsyncLocal key, out object value); - IAsyncLocalValueMap Set(IAsyncLocal key, object value); - } - - // - // Utility functions for getting/creating instances of IAsyncLocalValueMap - // - internal static class AsyncLocalValueMap - { - public static IAsyncLocalValueMap Empty { get; } = new EmptyAsyncLocalValueMap(); - - // Instance without any key/value pairs. Used as a singleton/ - private sealed class EmptyAsyncLocalValueMap : IAsyncLocalValueMap - { - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - // If the value isn't null, then create a new one-element map to store - // the key/value pair. If it is null, then we're still empty. - return value != null ? - new OneElementAsyncLocalValueMap(key, value) : - (IAsyncLocalValueMap)this; - } - - public bool TryGetValue(IAsyncLocal key, out object value) - { - value = null; - return false; - } - } - - // Instance with one key/value pair. - private sealed class OneElementAsyncLocalValueMap : IAsyncLocalValueMap - { - private readonly IAsyncLocal _key1; - private readonly object _value1; - - public OneElementAsyncLocalValueMap(IAsyncLocal key, object value) - { - _key1 = key; _value1 = value; - } - - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - if (value != null) - { - // The value is non-null. If the key matches one already contained in this map, - // then create a new one-element map with the updated value, otherwise create - // a two-element map with the additional key/value. - return ReferenceEquals(key, _key1) ? - new OneElementAsyncLocalValueMap(key, value) : - (IAsyncLocalValueMap)new TwoElementAsyncLocalValueMap(_key1, _value1, key, value); - } - else - { - // The value is null. If the key exists in this map, remove it by downgrading to an empty map. - // Otherwise, there's nothing to add or remove, so just return this map. - return ReferenceEquals(key, _key1) ? - Empty : - (IAsyncLocalValueMap)this; - } - } - - public bool TryGetValue(IAsyncLocal key, out object value) - { - if (ReferenceEquals(key, _key1)) - { - value = _value1; - return true; - } - else - { - value = null; - return false; - } - } - } - - // Instance with two key/value pairs. - private sealed class TwoElementAsyncLocalValueMap : IAsyncLocalValueMap - { - private readonly IAsyncLocal _key1, _key2; - private readonly object _value1, _value2; - - public TwoElementAsyncLocalValueMap(IAsyncLocal key1, object value1, IAsyncLocal key2, object value2) - { - _key1 = key1; _value1 = value1; - _key2 = key2; _value2 = value2; - } - - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - if (value != null) - { - // The value is non-null. If the key matches one already contained in this map, - // then create a new two-element map with the updated value, otherwise create - // a three-element map with the additional key/value. - return - ReferenceEquals(key, _key1) ? new TwoElementAsyncLocalValueMap(key, value, _key2, _value2) : - ReferenceEquals(key, _key2) ? new TwoElementAsyncLocalValueMap(_key1, _value1, key, value) : - (IAsyncLocalValueMap)new ThreeElementAsyncLocalValueMap(_key1, _value1, _key2, _value2, key, value); - } - else - { - // The value is null. If the key exists in this map, remove it by downgrading to a one-element map - // without the key. Otherwise, there's nothing to add or remove, so just return this map. - return - ReferenceEquals(key, _key1) ? new OneElementAsyncLocalValueMap(_key2, _value2) : - ReferenceEquals(key, _key2) ? new OneElementAsyncLocalValueMap(_key1, _value1) : - (IAsyncLocalValueMap)this; - } - } - - public bool TryGetValue(IAsyncLocal key, out object value) - { - if (ReferenceEquals(key, _key1)) - { - value = _value1; - return true; - } - else if (ReferenceEquals(key, _key2)) - { - value = _value2; - return true; - } - else - { - value = null; - return false; - } - } - } - - // Instance with three key/value pairs. - private sealed class ThreeElementAsyncLocalValueMap : IAsyncLocalValueMap - { - private readonly IAsyncLocal _key1, _key2, _key3; - private readonly object _value1, _value2, _value3; - - public ThreeElementAsyncLocalValueMap(IAsyncLocal key1, object value1, IAsyncLocal key2, object value2, IAsyncLocal key3, object value3) - { - _key1 = key1; _value1 = value1; - _key2 = key2; _value2 = value2; - _key3 = key3; _value3 = value3; - } - - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - if (value != null) - { - // The value is non-null. If the key matches one already contained in this map, - // then create a new three-element map with the updated value. - if (ReferenceEquals(key, _key1)) return new ThreeElementAsyncLocalValueMap(key, value, _key2, _value2, _key3, _value3); - if (ReferenceEquals(key, _key2)) return new ThreeElementAsyncLocalValueMap(_key1, _value1, key, value, _key3, _value3); - if (ReferenceEquals(key, _key3)) return new ThreeElementAsyncLocalValueMap(_key1, _value1, _key2, _value2, key, value); - - // The key doesn't exist in this map, so upgrade to a multi map that contains - // the additional key/value pair. - var multi = new MultiElementAsyncLocalValueMap(4); - multi.UnsafeStore(0, _key1, _value1); - multi.UnsafeStore(1, _key2, _value2); - multi.UnsafeStore(2, _key3, _value3); - multi.UnsafeStore(3, key, value); - return multi; - } - else - { - // The value is null. If the key exists in this map, remove it by downgrading to a two-element map - // without the key. Otherwise, there's nothing to add or remove, so just return this map. - return - ReferenceEquals(key, _key1) ? new TwoElementAsyncLocalValueMap(_key2, _value2, _key3, _value3) : - ReferenceEquals(key, _key2) ? new TwoElementAsyncLocalValueMap(_key1, _value1, _key3, _value3) : - ReferenceEquals(key, _key3) ? new TwoElementAsyncLocalValueMap(_key1, _value1, _key2, _value2) : - (IAsyncLocalValueMap)this; - } - } - - public bool TryGetValue(IAsyncLocal key, out object value) - { - if (ReferenceEquals(key, _key1)) - { - value = _value1; - return true; - } - else if (ReferenceEquals(key, _key2)) - { - value = _value2; - return true; - } - else if (ReferenceEquals(key, _key3)) - { - value = _value3; - return true; - } - else - { - value = null; - return false; - } - } - } - - // Instance with up to 16 key/value pairs. - private sealed class MultiElementAsyncLocalValueMap : IAsyncLocalValueMap - { - internal const int MaxMultiElements = 16; - private readonly KeyValuePair<IAsyncLocal, object>[] _keyValues; - - internal MultiElementAsyncLocalValueMap(int count) - { - Debug.Assert(count <= MaxMultiElements); - _keyValues = new KeyValuePair<IAsyncLocal, object>[count]; - } - - internal void UnsafeStore(int index, IAsyncLocal key, object value) - { - Debug.Assert(index < _keyValues.Length); - _keyValues[index] = new KeyValuePair<IAsyncLocal, object>(key, value); - } - - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - // Find the key in this map. - for (int i = 0; i < _keyValues.Length; i++) - { - if (ReferenceEquals(key, _keyValues[i].Key)) - { - // The key is in the map. If the value isn't null, then create a new map of the same - // size that has all of the same pairs, with this new key/value pair overwriting the old. - if (value != null) - { - var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length); - Array.Copy(_keyValues, 0, multi._keyValues, 0, _keyValues.Length); - multi._keyValues[i] = new KeyValuePair<IAsyncLocal, object>(key, value); - return multi; - } - else if (_keyValues.Length == 4) - { - // The value is null, and we only have four elements, one of which we're removing, - // so downgrade to a three-element map, without the matching element. - return - i == 0 ? new ThreeElementAsyncLocalValueMap(_keyValues[1].Key, _keyValues[1].Value, _keyValues[2].Key, _keyValues[2].Value, _keyValues[3].Key, _keyValues[3].Value) : - i == 1 ? new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[2].Key, _keyValues[2].Value, _keyValues[3].Key, _keyValues[3].Value) : - i == 2 ? new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[1].Key, _keyValues[1].Value, _keyValues[3].Key, _keyValues[3].Value) : - (IAsyncLocalValueMap)new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[1].Key, _keyValues[1].Value, _keyValues[2].Key, _keyValues[2].Value); - } - else - { - // The value is null, and we have enough elements remaining to warrant a multi map. - // Create a new one and copy all of the elements from this one, except the one to be removed. - var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length - 1); - if (i != 0) Array.Copy(_keyValues, 0, multi._keyValues, 0, i); - if (i != _keyValues.Length - 1) Array.Copy(_keyValues, i + 1, multi._keyValues, i, _keyValues.Length - i - 1); - return multi; - } - } - } - - // The key does not already exist in this map. - - // If the value is null, then we can simply return this same map, as there's nothing to add or remove. - if (value == null) - { - return this; - } - - // We need to create a new map that has the additional key/value pair. - // If with the addition we can still fit in a multi map, create one. - if (_keyValues.Length < MaxMultiElements) - { - var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length + 1); - Array.Copy(_keyValues, 0, multi._keyValues, 0, _keyValues.Length); - multi._keyValues[_keyValues.Length] = new KeyValuePair<IAsyncLocal, object>(key, value); - return multi; - } - - // Otherwise, upgrade to a many map. - var many = new ManyElementAsyncLocalValueMap(MaxMultiElements + 1); - foreach (KeyValuePair<IAsyncLocal, object> pair in _keyValues) - { - many[pair.Key] = pair.Value; - } - many[key] = value; - return many; - } - - public bool TryGetValue(IAsyncLocal key, out object value) - { - foreach (KeyValuePair<IAsyncLocal, object> pair in _keyValues) - { - if (ReferenceEquals(key, pair.Key)) - { - value = pair.Value; - return true; - } - } - value = null; - return false; - } - } - - // Instance with any number of key/value pairs. - private sealed class ManyElementAsyncLocalValueMap : Dictionary<IAsyncLocal, object>, IAsyncLocalValueMap - { - public ManyElementAsyncLocalValueMap(int capacity) : base(capacity) { } - - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) - { - int count = Count; - bool containsKey = ContainsKey(key); - - // If the value being set exists, create a new many map, copy all of the elements from this one, - // and then store the new key/value pair into it. This is the most common case. - if (value != null) - { - var map = new ManyElementAsyncLocalValueMap(count + (containsKey ? 0 : 1)); - foreach (KeyValuePair<IAsyncLocal, object> pair in this) - { - map[pair.Key] = pair.Value; - } - map[key] = value; - return map; - } - - // Otherwise, the value is null, which means null is being stored into an AsyncLocal.Value. - // Since there's no observable difference at the API level between storing null and the key - // not existing at all, we can downgrade to a smaller map rather than storing null. - - // If the key is contained in this map, we're going to create a new map that's one pair smaller. - if (containsKey) - { - // If the new count would be within range of a multi map instead of a many map, - // downgrade to the many map, which uses less memory and is faster to access. - // Otherwise, just create a new many map that's missing this key. - if (count == MultiElementAsyncLocalValueMap.MaxMultiElements + 1) - { - var multi = new MultiElementAsyncLocalValueMap(MultiElementAsyncLocalValueMap.MaxMultiElements); - int index = 0; - foreach (KeyValuePair<IAsyncLocal, object> pair in this) - { - if (!ReferenceEquals(key, pair.Key)) - { - multi.UnsafeStore(index++, pair.Key, pair.Value); - } - } - Debug.Assert(index == MultiElementAsyncLocalValueMap.MaxMultiElements); - return multi; - } - else - { - var map = new ManyElementAsyncLocalValueMap(count - 1); - foreach (KeyValuePair<IAsyncLocal, object> pair in this) - { - if (!ReferenceEquals(key, pair.Key)) - { - map[pair.Key] = pair.Value; - } - } - Debug.Assert(map.Count == count - 1); - return map; - } - } - - // We were storing null, but the key wasn't in the map, so there's nothing to change. - // Just return this instance. - return this; - } - } - } -} |