Ecosyste.ms: Awesome
An open API service indexing awesome lists of open source software.
https://github.com/bemobolo/bem.collections.weakdictionary
WeakDictionary using weak keys with the ability to use custom IEqualityComparer on them
https://github.com/bemobolo/bem.collections.weakdictionary
Last synced: about 2 months ago
JSON representation
WeakDictionary using weak keys with the ability to use custom IEqualityComparer on them
- Host: GitHub
- URL: https://github.com/bemobolo/bem.collections.weakdictionary
- Owner: bemobolo
- License: gpl-3.0
- Created: 2022-11-17T08:28:49.000Z (about 2 years ago)
- Default Branch: main
- Last Pushed: 2023-11-03T19:43:50.000Z (about 1 year ago)
- Last Synced: 2024-11-01T23:05:36.378Z (3 months ago)
- Language: C#
- Homepage:
- Size: 42 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Bem.Collections.WeakDictionary
# Overview
A thread-safe dictionary implementation that stores values with weekly referenced keys. See [`WeakReference`](https://learn.microsoft.com/en-us/dotnet/api/system.weakreference-1).
Once a key is not strong-referenced anymore the entry will be removed automatically from `WeakDictionary`.
This collection can be used for similar purposes as [`ConditionalWeakTable`](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.conditionalweaktable-2) except that `WeakDictionary` can accept custom [`IEqualityComparer`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.iequalitycomparer-1) instance for key comparison. [`ConditionalWeakTable`](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.conditionalweaktable-2) can only compare keys by reference no matter if [`GetHashCode()`](https://learn.microsoft.com/en-us/dotnet/api/system.object.gethashcode) and [`Equals()`](https://learn.microsoft.com/en-us/dotnet/api/system.object.equals) methods are overridden or not.
Internally `WeakDictionary` uses a combination of [`Dictionary`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2) and [`ConditionalWeakTable`](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.conditionalweaktable-2) types to manage entries.
# Usage
Use the same way as a generic [`Dictionary`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2).
```csharp
var dictionary = new WeakDictionary(optionalEqualityComparer);
```
Note that `WeakDictionary` implements only [`IDictionary`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic), [`IEnumerable`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ienumerable-1) and [`IEnumerable`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.ienumerable) interfaces.
Note that `TKey` must be reference type, but `TValue` can be anything you want.
**Also note that `TValue` by default is not stored as a [`WeakReference`](https://learn.microsoft.com/en-us/dotnet/api/system.weakreference-1). Therefore if key and value reference the same object GC can not collect the instance!**
Consider this if you plan to use `WeakDictionary` as a [`HashSet`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.hashset-1) and avoid using the same instance for key and value.
## Use Cases
The single use case of this library is when you need to use a custom [`IEqualityComparer`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.iequalitycomparer-1) for the weakly referenced keys. If this is not a requirement use the [`ConditionalWeakTable`](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.conditionalweaktable-2) instead.
# Thread Safety
All public and protected members of `WeakDictionary` are thread-safe and may be used concurrently from multiple threads. However, members accessed through one of the interfaces the `WeakDictionary` implements, including extension methods, are not guaranteed to be thread safe and may need to be synchronized by the caller.
# Benchmarks
The below results show that `WeakDictionary` has some performance cost compared to the other data structures probably because of all the locks surrounding the logic of the internal data structure mutations.
## Runtime=.NET 7.0
### Populating
| Method | N | Mean | Error | StdDev | Ratio | RatioSD |
|------------------------- |------- |----------:|-----------:|---------:|------:|--------:|
| WeakDictionary_Add | 100000 | 217.97 ms | 117.891 ms | 6.462 ms | 4.56 | 1.12 |
| ConcurrentDictionary_Add | 100000 | 49.66 ms | 9.680 ms | 0.531 ms | 1.04 | 0.24 |
| Dictionary_Add | 100000 | 18.18 ms | 47.396 ms | 2.598 ms | 0.37 | 0.07 |
| ConditionalWeakTable_Add | 100000 | 49.44 ms | 177.786 ms | 9.745 ms | 1.00 | 0.00 |
### Getting items
| Method | N | Mean | Error | StdDev | Ratio | RatioSD |
|--------------------------------- |------- |---------:|---------:|---------:|------:|--------:|
| WeakDictionary_TryGetValue | 100000 | 71.26 ms | 48.43 ms | 2.655 ms | 2.09 | 0.27 |
| ConcurrentDictionary_TryGetValue | 100000 | 12.10 ms | 36.76 ms | 2.015 ms | 0.35 | 0.04 |
| Dictionary_TryGetValue | 100000 | 20.75 ms | 31.57 ms | 1.730 ms | 0.61 | 0.09 |
| ConditionalWeakTable_TryGetValue | 100000 | 34.57 ms | 89.00 ms | 4.879 ms | 1.00 | 0.00 |
### Updating items
| Method | N | Mean | Error | StdDev | Ratio | RatioSD |
|------------------------- |------- |----------:|----------:|----------:|------:|--------:|
| WeakDictionary_Set | 100000 | 378.94 ms | 746.94 ms | 40.942 ms | 18.87 | 0.79 |
| ConcurrentDictionary_Set | 100000 | 26.72 ms | 32.10 ms | 1.759 ms | 1.33 | 0.04 |
| Dictionary_Set | 100000 | 22.34 ms | 17.56 ms | 0.963 ms | 1.12 | 0.14 |
| ConditionalWeakTable_Set | 100000 | 20.07 ms | 33.44 ms | 1.833 ms | 1.00 | 0.00 |
### Removing items
| Method | N | Mean | Error | StdDev | Ratio | RatioSD |
|---------------------------- |------- |----------:|----------:|----------:|------:|--------:|
| WeakDictionary_Remove | 100000 | 130.70 ms | 262.21 ms | 14.373 ms | 8.85 | 3.03 |
| ConcurrentDictionary_Remove | 100000 | 23.11 ms | 38.31 ms | 2.100 ms | 1.53 | 0.26 |
| Dictionary_Remove | 100000 | 14.89 ms | 39.01 ms | 2.138 ms | 0.99 | 0.22 |
| ConditionalWeakTable_Remove | 100000 | 15.49 ms | 59.07 ms | 3.238 ms | 1.00 | 0.00 |