diff options
Diffstat (limited to 'src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs')
| -rw-r--r-- | src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs | 120 |
1 files changed, 67 insertions, 53 deletions
diff --git a/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs b/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs index 3531265be..12d650243 100644 --- a/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs +++ b/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs @@ -61,7 +61,7 @@ namespace System.Threading get { object obj = ExecutionContext.GetLocalValue(this); - return (obj == null) ? default(T) : (T)obj; + return (obj == null) ? default : (T)obj; } set { @@ -72,8 +72,8 @@ namespace System.Threading 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; + T previousValue = previousValueObj == null ? default : (T)previousValueObj; + T currentValue = currentValueObj == null ? default : (T)currentValueObj; m_valueChangedHandler(new AsyncLocalValueChangedArgs<T>(previousValue, currentValue, contextChanged)); } } @@ -86,19 +86,18 @@ namespace System.Threading void OnValueChanged(object previousValue, object currentValue, bool contextChanged); } - public struct AsyncLocalValueChangedArgs<T> + public readonly struct AsyncLocalValueChangedArgs<T> { - public T PreviousValue { get; private set; } - public T CurrentValue { get; private set; } + public T PreviousValue { get; } + public T CurrentValue { get; } // // 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; } + public bool ThreadContextChanged { get; } internal AsyncLocalValueChangedArgs(T previousValue, T currentValue, bool contextChanged) - : this() { PreviousValue = previousValue; CurrentValue = currentValue; @@ -114,7 +113,7 @@ namespace System.Threading internal interface IAsyncLocalValueMap { bool TryGetValue(IAsyncLocal key, out object value); - IAsyncLocalValueMap Set(IAsyncLocal key, object value); + IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent); } // @@ -124,14 +123,31 @@ namespace System.Threading { public static IAsyncLocalValueMap Empty { get; } = new EmptyAsyncLocalValueMap(); + public static bool IsEmpty(IAsyncLocalValueMap asyncLocalValueMap) + { + Debug.Assert(asyncLocalValueMap != null); + Debug.Assert(asyncLocalValueMap == Empty || asyncLocalValueMap.GetType() != typeof(EmptyAsyncLocalValueMap)); + + return asyncLocalValueMap == Empty; + } + + public static IAsyncLocalValueMap Create(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) + { + // If the value isn't null or a null value may not be treated as nonexistent, then create a new one-element map + // to store the key/value pair. Otherwise, use the empty map. + return value != null || !treatNullValueAsNonexistent ? + new OneElementAsyncLocalValueMap(key, value) : + Empty; + } + // Instance without any key/value pairs. Used as a singleton/ - internal sealed class EmptyAsyncLocalValueMap : IAsyncLocalValueMap + private sealed class EmptyAsyncLocalValueMap : IAsyncLocalValueMap { - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { - // 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 ? + // If the value isn't null or a null value may not be treated as nonexistent, then create a new one-element map + // to store the key/value pair. Otherwise, use the empty map. + return value != null || !treatNullValueAsNonexistent ? new OneElementAsyncLocalValueMap(key, value) : (IAsyncLocalValueMap)this; } @@ -144,7 +160,7 @@ namespace System.Threading } // Instance with one key/value pair. - internal sealed class OneElementAsyncLocalValueMap : IAsyncLocalValueMap + private sealed class OneElementAsyncLocalValueMap : IAsyncLocalValueMap { private readonly IAsyncLocal _key1; private readonly object _value1; @@ -154,21 +170,20 @@ namespace System.Threading _key1 = key; _value1 = value; } - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { - if (value != null) + if (value != null || !treatNullValueAsNonexistent) { - // 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. + // 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. + // 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; @@ -202,13 +217,12 @@ namespace System.Threading _key2 = key2; _value2 = value2; } - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { - if (value != null) + if (value != null || !treatNullValueAsNonexistent) { - // 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. + // 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) : @@ -216,8 +230,8 @@ namespace System.Threading } 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. + // 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) : @@ -258,12 +272,12 @@ namespace System.Threading _key3 = key3; _value3 = value3; } - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { - if (value != null) + if (value != null || !treatNullValueAsNonexistent) { - // 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 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); @@ -279,8 +293,8 @@ namespace System.Threading } 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. + // 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) : @@ -332,17 +346,18 @@ namespace System.Threading _keyValues[index] = new KeyValuePair<IAsyncLocal, object>(key, value); } - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { // 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) + // The key is in the map. + if (value != null || !treatNullValueAsNonexistent) { + // Create a new map of the same size that has all of the same pairs, with this new key/value pair + // overwriting the old. var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length); Array.Copy(_keyValues, 0, multi._keyValues, 0, _keyValues.Length); multi._keyValues[i] = new KeyValuePair<IAsyncLocal, object>(key, value); @@ -350,8 +365,8 @@ namespace System.Threading } 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. + // 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) : @@ -360,8 +375,8 @@ namespace System.Threading } 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. + // 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); @@ -372,9 +387,9 @@ namespace System.Threading // 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) + if (value == null && treatNullValueAsNonexistent) { + // We can simply return this same map, as there's nothing to add or remove. return this; } @@ -418,14 +433,14 @@ namespace System.Threading { public ManyElementAsyncLocalValueMap(int capacity) : base(capacity) { } - public IAsyncLocalValueMap Set(IAsyncLocal key, object value) + public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent) { 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) + if (value != null || !treatNullValueAsNonexistent) { var map = new ManyElementAsyncLocalValueMap(count + (containsKey ? 0 : 1)); foreach (KeyValuePair<IAsyncLocal, object> pair in this) @@ -436,15 +451,14 @@ namespace System.Threading 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. + // Otherwise, the value is null and a null value may be treated as nonexistent. 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. + // downgrade to the multi 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) { @@ -475,8 +489,8 @@ namespace System.Threading } } - // We were storing null, but the key wasn't in the map, so there's nothing to change. - // Just return this instance. + // We were storing null and a null value may be treated as nonexistent, but the key wasn't in the map, so + // there's nothing to change. Just return this instance. return this; } } |