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Add fast path to Array.ConstrainedCopy for single-dimensional arrays #122530

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Merged
jkotas merged 4 commits into from
Dec 17, 2025
+15 −5
Merged

Add fast path to Array.ConstrainedCopy for single-dimensional arrays #122530

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826e080
Initial plan
Copilot Dec 14, 2025
872fdc5
Add fast path to Array.ConstrainedCopy for single-dimensional arrays
Copilot Dec 14, 2025
8762e82
Merge ConstrainedCopy into !MONO block and add Mono implementation
Copilot Dec 14, 2025
c7faa5f
Refactor to use shared Copy helper method with reliable parameter
Copilot Dec 15, 2025
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15 changes: 10 additions & 5 deletions src/libraries/System.Private.CoreLib/src/System/Array.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -352,18 +352,18 @@ public static void Copy(Array sourceArray, long sourceIndex, Array destinationAr
Copy(sourceArray, isourceIndex, destinationArray, idestinationIndex, ilength);
}

#if !MONO // implementation details of MethodTable

// Provides a strong exception guarantee - either it succeeds, or
// it throws an exception with no side effects. The arrays must be
// compatible array types based on the array element type - this
// method does not support casting, boxing, or primitive widening.
// It will up-cast, assuming the array types are correct.
public static void ConstrainedCopy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
{
CopyImpl(sourceArray, sourceIndex, destinationArray, destinationIndex, length, reliable: true);
Copy(sourceArray, sourceIndex, destinationArray, destinationIndex, length, reliable: true);
}

#if !MONO // implementation details of MethodTable

// Copies length elements from sourceArray, starting at index 0, to
// destinationArray, starting at index 0.
public static unsafe void Copy(Array sourceArray, Array destinationArray, int length)
Expand Down Expand Up @@ -396,7 +396,12 @@ public static unsafe void Copy(Array sourceArray, Array destinationArray, int le

// Copies length elements from sourceArray, starting at sourceIndex, to
// destinationArray, starting at destinationIndex.
public static unsafe void Copy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
public static void Copy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
{
Copy(sourceArray, sourceIndex, destinationArray, destinationIndex, length, reliable: false);
}

private static unsafe void Copy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length, bool reliable)
{
if (sourceArray != null && destinationArray != null)
{
Expand All @@ -423,7 +428,7 @@ public static unsafe void Copy(Array sourceArray, int sourceIndex, Array destina
}

// Less common
CopyImpl(sourceArray, sourceIndex, destinationArray, destinationIndex, length, reliable: false);
CopyImpl(sourceArray, sourceIndex, destinationArray, destinationIndex, length, reliable);
}

// Reliability-wise, this method will either possibly corrupt your
Expand Down
5 changes: 5 additions & 0 deletions src/mono/System.Private.CoreLib/src/System/Array.Mono.cs
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Expand Up @@ -106,6 +106,11 @@ public static void Copy(Array sourceArray, int sourceIndex, Array destinationArr
CopyImpl(sourceArray, sourceIndex, destinationArray, destinationIndex, length, false);
}

public static void ConstrainedCopy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
{
CopyImpl(sourceArray, sourceIndex, destinationArray, destinationIndex, length, true);
}

private static void CopyImpl(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length, bool reliable)
{
ArgumentNullException.ThrowIfNull(sourceArray);
Expand Down
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