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Copy in blocks in StringBuilder.CopyTo(int, Span<char>, int) #694

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Merged
SimonCropp merged 1 commit into from
Oct 12, 2026
Merged

Copy in blocks in StringBuilder.CopyTo(int, Span<char>, int) #694

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23 changes: 21 additions & 2 deletions src/Polyfill/Polyfill_StringBuilder_CopyTo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
namespace Polyfills;

using System;
using System.Buffers;
using System.Text;

static partial class Polyfill
Expand Down Expand Up @@ -37,9 +38,27 @@ public static void CopyTo(
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}

for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}

// The indexer walks the chunk list on every call, so copy in blocks through the array overload instead.
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net461/Polyfill_StringBuilder_CopyTo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net462/Polyfill_StringBuilder_CopyTo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net47/Polyfill_StringBuilder_CopyTo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net471/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net472/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net48/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/net481/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/netcoreapp2.0/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/netstandard2.0/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
21 changes: 19 additions & 2 deletions src/Split/uap10.0/Polyfill_StringBuilder_CopyTo.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#if FeatureMemory
namespace Polyfills;
using System;
using System.Buffers;
using System.Text;
static partial class Polyfill
{
Expand Down Expand Up @@ -31,9 +32,25 @@ public static void CopyTo(
{
throw new ArgumentException("The destination span is too short to hold the requested characters.", nameof(destination));
}
for (var index = 0; index < count; index++)
if (count == 0)
{
destination[index] = target[sourceIndex + index];
return;
}
var buffer = ArrayPool<char>.Shared.Rent(Math.Min(count, 16384));
try
{
var copied = 0;
while (copied < count)
{
var length = Math.Min(count - copied, buffer.Length);
target.CopyTo(sourceIndex + copied, buffer, 0, length);
buffer.AsSpan(0, length).CopyTo(destination.Slice(copied));
copied += length;
}
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
}
Expand Down
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