You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
154 lines
8.2 KiB
154 lines
8.2 KiB
using System;
|
|
using System.Collections;
|
|
using System.Collections.Concurrent;
|
|
using System.Collections.Generic;
|
|
using System.Diagnostics;
|
|
using System.Linq;
|
|
using System.Reflection;
|
|
using System.Text;
|
|
using System.Threading;
|
|
using System.Threading.Tasks;
|
|
|
|
namespace IPA.Utilities.Async
|
|
{
|
|
/// <summary>
|
|
/// A dictionary-like type intended for thread-safe value caches whose values are created only once ever.
|
|
/// </summary>
|
|
/// <typeparam name="TKey">the key type of the cache</typeparam>
|
|
/// <typeparam name="TValue">the value type of the cache</typeparam>
|
|
/// <remarks>
|
|
/// This object basically wraps a <see cref="ConcurrentDictionary{TKey, TValue}"/> with some special handling
|
|
/// to ensure that values are only created once ever, without having multiple parallel constructions.
|
|
/// </remarks>
|
|
public class SingleCreationValueCache<TKey, TValue>
|
|
{
|
|
private readonly ConcurrentDictionary<TKey, (ManualResetEventSlim wh, TValue val)> dict;
|
|
|
|
private static KeyValuePair<TKey, (ManualResetEventSlim, TValue)> ExpandKeyValuePair(KeyValuePair<TKey, TValue> kvp)
|
|
=> new KeyValuePair<TKey, (ManualResetEventSlim, TValue)>(kvp.Key, (null, kvp.Value));
|
|
private static KeyValuePair<TKey, TValue> CompressKeyValuePair(KeyValuePair<TKey, (ManualResetEventSlim, TValue value)> kvp)
|
|
=> new KeyValuePair<TKey, TValue>(kvp.Key, kvp.Value.value);
|
|
|
|
#region Constructors
|
|
/// <summary>
|
|
/// Initializes a new instance of the <see cref="SingleCreationValueCache{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.
|
|
/// </summary>
|
|
public SingleCreationValueCache()
|
|
=> dict = new ConcurrentDictionary<TKey, (ManualResetEventSlim wh, TValue val)>();
|
|
/// <summary>
|
|
/// Initializes a new instance of the <see cref="SingleCreationValueCache{TKey, TValue}"/>
|
|
/// class that contains elements copied from the specified <see cref="IEnumerable{T}"/>,
|
|
/// has the default concurrency level, has the default initial capacity, and uses
|
|
/// the default comparer for the key type.
|
|
/// </summary>
|
|
/// <param name="collection">the <see cref="IEnumerable{T}"/> whose element are to be used for the new cache</param>
|
|
/// <exception cref="ArgumentNullException">when any arguments are null</exception>
|
|
/// <exception cref="ArgumentException"><paramref name="collection"/> contains duplicate keys</exception>
|
|
public SingleCreationValueCache(IEnumerable<KeyValuePair<TKey, TValue>> collection)
|
|
=> dict = new ConcurrentDictionary<TKey, (ManualResetEventSlim wh, TValue val)>(collection.Select(ExpandKeyValuePair));
|
|
/// <summary>
|
|
/// Initializes a new instance of the <see cref="SingleCreationValueCache{TKey, TValue}"/>
|
|
/// class that is empty, has the default concurrency level and capacity, and uses
|
|
/// the specified <see cref="IEqualityComparer{T}"/>.
|
|
/// </summary>
|
|
/// <param name="comparer">the equality comparer to use when comparing keys</param>
|
|
/// <exception cref="ArgumentNullException"><paramref name="comparer"/> is null</exception>
|
|
public SingleCreationValueCache(IEqualityComparer<TKey> comparer)
|
|
=> dict = new ConcurrentDictionary<TKey, (ManualResetEventSlim wh, TValue val)>(comparer);
|
|
/// <summary>
|
|
/// Initializes a new instance of the <see cref="SingleCreationValueCache{TKey, TValue}"/>
|
|
/// class that contains elements copied from the specified <see cref="IEnumerable{T}"/>
|
|
/// has the default concurrency level, has the default initial capacity, and uses
|
|
/// the specified <see cref="IEqualityComparer{T}"/>.
|
|
/// </summary>
|
|
/// <param name="collection">the <see cref="IEnumerable{T}"/> whose elements are to be used for the new cache</param>
|
|
/// <param name="comparer">the equality comparer to use when comparing keys</param>
|
|
/// <exception cref="ArgumentNullException"><paramref name="collection"/> or <paramref name="comparer"/> is null</exception>
|
|
public SingleCreationValueCache(IEnumerable<KeyValuePair<TKey, TValue>> collection, IEqualityComparer<TKey> comparer)
|
|
=> dict = new ConcurrentDictionary<TKey, (ManualResetEventSlim wh, TValue val)>(collection.Select(ExpandKeyValuePair), comparer);
|
|
#endregion
|
|
|
|
/// <summary>
|
|
/// Gets a value that indicates whether this cache is empty.
|
|
/// </summary>
|
|
public bool IsEmpty => dict.IsEmpty;
|
|
/// <summary>
|
|
/// Gets the number of elements that this cache contains.
|
|
/// </summary>
|
|
public int Count => dict.Count;
|
|
|
|
/// <summary>
|
|
/// Clears the cache.
|
|
/// </summary>
|
|
public void Clear() => dict.Clear();
|
|
/// <summary>
|
|
/// Gets a value indicating whether or not this cache contains <paramref name="key"/>.
|
|
/// </summary>
|
|
/// <param name="key">the key to search for</param>
|
|
/// <returns><see langword="true"/> if the cache contains the key, <see langword="false"/> otherwise</returns>
|
|
public bool ContainsKey(TKey key) => dict.ContainsKey(key);
|
|
/// <summary>
|
|
/// Copies the key-value pairs stored by the cache to a new array, filtering all elements that are currently being
|
|
/// created.
|
|
/// </summary>
|
|
/// <returns>an array containing a snapshot of the key-value pairs contained in this cache</returns>
|
|
public KeyValuePair<TKey, TValue>[] ToArray()
|
|
=> dict.ToArray().Where(k => k.Value.wh == null).Select(CompressKeyValuePair).ToArray();
|
|
|
|
/// <summary>
|
|
/// Attempts to get the value associated with the specified key from the cache.
|
|
/// </summary>
|
|
/// <param name="key">the key to search for</param>
|
|
/// <param name="value">the value retrieved, if any</param>
|
|
/// <returns><see langword="true"/> if the value was found, <see langword="false"/> otherwise</returns>
|
|
public bool TryGetValue(TKey key, out TValue value)
|
|
{
|
|
if (dict.TryGetValue(key, out var pair) && pair.wh == null)
|
|
{
|
|
value = pair.val;
|
|
return true;
|
|
}
|
|
value = default;
|
|
return false;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Gets the value associated with the specified key from the cache. If it does not exist, and
|
|
/// no creators are currently running for this key, then the creator is called to create the value
|
|
/// and the value is added to the cache. If there is a creator currently running for the key, then
|
|
/// this waits for the creator to finish and retrieves the value.
|
|
/// </summary>
|
|
/// <param name="key">the key to search for</param>
|
|
/// <param name="creator">the delegate to use to create the value if it does not exist</param>
|
|
/// <returns>the value that was found, or the result of <paramref name="creator"/></returns>
|
|
public TValue GetOrAdd(TKey key, Func<TKey, TValue> creator)
|
|
{
|
|
retry:
|
|
if (dict.TryGetValue(key, out var value))
|
|
{
|
|
if (value.wh != null)
|
|
{
|
|
value.wh.Wait();
|
|
goto retry; // this isn't really a good candidate for a loop
|
|
// the loop condition will never be hit, and this should only
|
|
// jump back to the beginning in exceptional situations
|
|
}
|
|
return value.val;
|
|
}
|
|
else
|
|
{
|
|
var wh = new ManualResetEventSlim(false);
|
|
var cmp = (wh, default(TValue));
|
|
if (!dict.TryAdd(key, cmp))
|
|
goto retry; // someone else beat us to the punch, retry getting their value and wait for them
|
|
var val = creator(key);
|
|
while (!dict.TryUpdate(key, (null, val), cmp))
|
|
throw new InvalidOperationException();
|
|
wh.Set();
|
|
return val;
|
|
}
|
|
}
|
|
}
|
|
}
|