Add Random.Shuffle() (#192)

SimonCropp · Jul 1, 2024 · 6c1b1ff · 6c1b1ff
1 parent d99166a
commit 6c1b1ff
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Showing 5 changed files with 99 additions and 12 deletions.
diff --git a/apiCount.include.md b/apiCount.include.md
@@ -1 +1 @@
-**API count: 297**
+**API count: 299**
diff --git a/api_list.include.md b/api_list.include.md
@@ -196,6 +196,8 @@
 #### Random
 
  * `Void NextBytes(Span<Byte>)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.random.nextbytes#system-random-nextbytes(system-span((system-byte))))
+ * `Void Shuffle<T>(T[])` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.random.nextbytes#system-random-nextbytes(system-span((system-byte))))
+ * `Void Shuffle<T>(Span<T>)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.random.nextbytes#system-random-nextbytes(system-span((system-byte))))
 
 
 #### ReadOnlySpan<Char>

diff --git a/src/Consume/Consume.cs b/src/Consume/Consume.cs
@@ -460,16 +460,26 @@ void GetMemberWithSameMetadataDefinitionAs(MemberInfo info)
 #if FeatureMemory
     void RandomNextBytesSpan()
     {
-        // Create a new instance of Random
         var random = new Random();
-
-        // Create a span of bytes
         Span<byte> buffer = new byte[10];
-
-        // Fill the span with random bytes
         random.NextBytes(buffer);
     }
+
+    void RandomShuffleSpan()
+    {
+        var random = new Random();
+        Span<byte> span = new byte[10];
+        random.Shuffle(span);
+    }
 #endif
+
+    void RandomShuffle()
+    {
+        var random = new Random();
+        var buffer = new byte[10];
+        random.Shuffle(buffer);
+    }
+
     public void SortedList()
     {
         var list = new SortedList<int, char>();

diff --git a/src/Polyfill/Polyfill_Random.cs b/src/Polyfill/Polyfill_Random.cs
@@ -24,4 +24,67 @@ public static void NextBytes(
         array.CopyTo(buffer);
     }
 #endif
+
+#if !NET8_0_OR_GREATER
+
+    /// <summary>
+    /// Performs an in-place shuffle of an array.
+    /// </summary>
+    /// <param name="index">The array to shuffle.</param>
+    /// <typeparam name="T">The type of array.</typeparam>
+    /// <remarks>
+    ///   This method uses <see cref="Next(int, int)" /> to choose values for shuffling.
+    ///   This method is an O(n) operation.
+    /// </remarks>
+    [Link("https://learn.microsoft.com/en-us/dotnet/api/system.random.nextbytes#system-random-nextbytes(system-span((system-byte)))")]
+    public static void Shuffle<T>(
+        this Random target,
+        T[] values)
+    {
+        int n = values.Length;
+
+        for (int i = 0; i < n - 1; i++)
+        {
+            int j = target.Next(i, n);
+
+            if (j != i)
+            {
+                T temp = values[i];
+                values[i] = values[j];
+                values[j] = temp;
+            }
+        }
+    }
+#if FeatureMemory
+
+    /// <summary>
+    /// Performs an in-place shuffle of a span.
+    /// </summary>
+    /// <param name="index">The span to shuffle.</param>
+    /// <typeparam name="T">The type of span.</typeparam>
+    /// <remarks>
+    ///   This method uses <see cref="Next(int, int)" /> to choose values for shuffling.
+    ///   This method is an O(n) operation.
+    /// </remarks>
+    [Link("https://learn.microsoft.com/en-us/dotnet/api/system.random.nextbytes#system-random-nextbytes(system-span((system-byte)))")]
+    public static void Shuffle<T>(
+        this Random target,
+        Span<T> values)
+    {
+        int n = values.Length;
+
+        for (int i = 0; i < n - 1; i++)
+        {
+            int j = target.Next(i, n);
+
+            if (j != i)
+            {
+                T temp = values[i];
+                values[i] = values[j];
+                values[j] = temp;
+            }
+        }
+    }
+#endif
+#endif
 }
diff --git a/src/Tests/PolyfillTests_Random.cs b/src/Tests/PolyfillTests_Random.cs
@@ -4,17 +4,29 @@ partial class PolyfillTests
     [Test]
     public void RandomNextBytesSpan()
     {
-        // Create a new instance of Random
         var random = new Random();
-
-        // Create a span of bytes
         Span<byte> buffer = new byte[10];
-
-        // Fill the span with random bytes
         random.NextBytes(buffer);
+        Assert.IsTrue(buffer.ToArray().Any(b => b != 0));
+    }
 
-        // Assert that the span is filled with random bytes
+    [Test]
+    public void RandomShuffleSpan()
+    {
+        var random = new Random();
+        Span<byte> buffer = new byte[10];
+        random.NextBytes(buffer);
+        random.Shuffle(buffer);
         Assert.IsTrue(buffer.ToArray().Any(b => b != 0));
     }
 #endif
+    [Test]
+    public void RandomShuffleArray()
+    {
+        var random = new Random();
+        var buffer = new byte[10];
+        random.NextBytes(buffer);
+        random.Shuffle(buffer);
+        Assert.IsTrue(buffer.ToArray().Any(b => b != 0));
+    }
 }