Skip to content

Optimize large buffer allocations with ArrayPool #78

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Tyrrrz merged 9 commits into from
Feb 17, 2026
Merged

Optimize large buffer allocations with ArrayPool #78

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
9 commits
Select commit Hold shift + click to select a range
375f042
Initial plan
Copilot Feb 17, 2026
81a3dd6
Replace array allocations with ArrayPool for memory optimization
Copilot Feb 17, 2026
b9e4bd0
Revert ArrayPool changes for small buffers - not beneficial
Copilot Feb 17, 2026
fbe7c1d
Fix TextReader.ReadAsync to correctly slice pooled buffer
Copilot Feb 17, 2026
c0c62e9
Add buffer size constants for clarity and consistency
Copilot Feb 17, 2026
a132bff
Address PR feedback: rename variable, inline expressions, use MemoryP…
Copilot Feb 17, 2026
d57680f
Address feedback: rename to buffer, append char-by-char, simplify sli…
Copilot Feb 17, 2026
65c8a88
Inline span variable access in char-by-char append loops
Copilot Feb 17, 2026
f2b8c03
Incorporate review feedback: use ArrayPool with array-based ReadAsync…
Copilot Feb 17, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 15 additions & 8 deletions PolyShim/Net50/Convert.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.Buffers;
using System.Diagnostics.CodeAnalysis;

[ExcludeFromCodeCoverage]
Expand Down Expand Up @@ -48,17 +49,23 @@ static int GetHexValue(char c)
// https://learn.microsoft.com/dotnet/api/system.convert.tohexstring#system-convert-tohexstring(system-byte()-system-int32-system-int32)
public static string ToHexString(byte[] value, int startIndex, int length)
{
var c = new char[length * 2];
var c = ArrayPool<char>.Shared.Rent(length * 2);

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Let's rename this to var chars

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in a132bff - renamed c to chars

try
{
for (var i = 0; i < length; i++)
{
var b = value[startIndex + i] >> 4;
c[i * 2] = (char)(55 + b + (((b - 10) >> 31) & -7));
b = value[startIndex + i] & 0xF;
c[i * 2 + 1] = (char)(55 + b + (((b - 10) >> 31) & -7));
}

for (var i = 0; i < length; i++)
return new string(c, 0, length * 2);
}
finally
{
var b = value[startIndex + i] >> 4;
c[i * 2] = (char)(55 + b + (((b - 10) >> 31) & -7));
b = value[startIndex + i] & 0xF;
c[i * 2 + 1] = (char)(55 + b + (((b - 10) >> 31) & -7));
ArrayPool<char>.Shared.Return(c);
}

return new string(c);
}

// https://learn.microsoft.com/dotnet/api/system.convert.tohexstring#system-convert-tohexstring(system-byte())
Expand Down
29 changes: 18 additions & 11 deletions PolyShim/Net70/TextReader.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.Buffers;
using System.IO;
using System.Text;
using System.Threading;
Expand All @@ -30,21 +31,27 @@ internal static class MemberPolyfills_Net70_TextReader
public async Task<string> ReadToEndAsync(CancellationToken cancellationToken)
{
var result = new StringBuilder();
var buffer = new char[4096];

while (true)
var buffer = ArrayPool<char>.Shared.Rent(4096);

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Maybe can use MemoryPool here, no? And in other places where async methods that support Memory are used.

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in a132bff - switched to MemoryPool for cleaner disposal pattern. Note: StringBuilder doesn't support Span/Memory append in older frameworks, so we convert the Memory slice to string (which allocates, but is necessary for compatibility).

try
{
var charsRead = await reader
.ReadAsync(buffer, cancellationToken)
.ConfigureAwait(false);
while (true)
{
var charsRead = await reader
.ReadAsync(buffer, cancellationToken)
.ConfigureAwait(false);

if (charsRead <= 0)
break;
if (charsRead <= 0)
break;

result.Append(buffer, 0, charsRead);
}
result.Append(buffer, 0, charsRead);
}

return result.ToString();
return result.ToString();
}
finally
{
ArrayPool<char>.Shared.Return(buffer);
}
}
#endif
}
Expand Down
19 changes: 15 additions & 4 deletions PolyShim/Net80/RandomNumberGenerator.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.Buffers;
using System.Text;
using System.Diagnostics.CodeAnalysis;
using System.Security.Cryptography;
Expand Down Expand Up @@ -46,11 +47,21 @@ public static void Shuffle<T>(Span<T> items)
// https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.gethexstring#system-security-cryptography-randomnumbergenerator-gethexstring(system-int32-system-boolean)
public static string GetHexString(int stringLength, bool lowercase = false)
{
var bytes = new byte[(stringLength + 1) / 2];
RandomNumberGenerator.Fill(bytes);
var byteCount = (stringLength + 1) / 2;

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can be inlined?

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in a132bff - inlined byteCount calculation

var bytes = ArrayPool<byte>.Shared.Rent(byteCount);
try
{
RandomNumberGenerator.Fill(bytes.AsSpan(0, byteCount));

var hex = lowercase ? Convert.ToHexStringLower(bytes) : Convert.ToHexString(bytes);
return hex.Substring(0, stringLength);
var hex = lowercase
? Convert.ToHexStringLower(bytes, 0, byteCount)
: Convert.ToHexString(bytes, 0, byteCount);
return hex.Substring(0, stringLength);
}
finally
{
ArrayPool<byte>.Shared.Return(bytes);

Copilot AI Feb 17, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Consider returning the rented byte[] with clearArray: true. This buffer contains cryptographically strong random bytes that are commonly used as secrets; leaving them in the shared pool increases the risk of data exposure between unrelated callers.

Suggested change
ArrayPool<byte>.Shared.Return(bytes);
ArrayPool<byte>.Shared.Return(bytes, clearArray: true);

Copilot uses AI. Check for mistakes.
}
}

// https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.getstring
Expand Down
20 changes: 14 additions & 6 deletions PolyShim/NetCore10/Stream.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
// ReSharper disable InconsistentNaming
// ReSharper disable PartialTypeWithSinglePart

using System.Buffers;
using System.IO;
using System.Diagnostics.CodeAnalysis;

Expand All @@ -16,14 +17,21 @@ internal static class MemberPolyfills_NetCore10_Stream
// https://learn.microsoft.com/dotnet/api/system.io.stream.copyto#system-io-stream-copyto(system-io-stream-system-int32)
public void CopyTo(Stream destination, int bufferSize)
{
var buffer = new byte[bufferSize];
while (true)
var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
try
{
var bytesRead = source.Read(buffer, 0, buffer.Length);
if (bytesRead <= 0)
break;
while (true)
{
var bytesRead = source.Read(buffer, 0, bufferSize);

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Read up to buffer.Length

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in d57680f - changed to read up to buffer.Length

if (bytesRead <= 0)
break;

destination.Write(buffer, 0, bytesRead);
destination.Write(buffer, 0, bytesRead);
}
}
finally
{
ArrayPool<byte>.Shared.Return(buffer);
}
}

Expand Down
45 changes: 29 additions & 16 deletions PolyShim/NetCore20/File.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
// ReSharper disable InconsistentNaming
// ReSharper disable PartialTypeWithSinglePart

using System.Buffers;
using System.Collections.Generic;
using System.IO;
using System.Text;
Expand Down Expand Up @@ -134,18 +135,24 @@ public static async Task<string> ReadAllTextAsync(string path, CancellationToken
using var reader = new StreamReader(stream);

var content = new StringBuilder();
var buffer = new char[4096];
var buffer = ArrayPool<char>.Shared.Rent(4096);
try
{
cancellationToken.ThrowIfCancellationRequested();

cancellationToken.ThrowIfCancellationRequested();
int charsRead;
while ((charsRead = await reader.ReadAsync(buffer, 0, 4096).ConfigureAwait(false)) > 0)

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can read into entire buffer, it's okay if there's more bytes

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in a132bff - changed to read into full buffer (buffer.Length) instead of limiting to bufferSize

{
cancellationToken.ThrowIfCancellationRequested();
content.Append(buffer, 0, charsRead);
}

int charsRead;
while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
return content.ToString();
}
finally
{
cancellationToken.ThrowIfCancellationRequested();
content.Append(buffer, 0, charsRead);
ArrayPool<char>.Shared.Return(buffer);
}

return content.ToString();
}

// https://learn.microsoft.com/dotnet/api/system.io.file.readalltextasync#system-io-file-readalltextasync(system-string-system-text-encoding-system-threading-cancellationtoken)
Expand All @@ -155,18 +162,24 @@ public static async Task<string> ReadAllTextAsync(string path, Encoding encoding
using var reader = new StreamReader(stream, encoding);

var content = new StringBuilder();
var buffer = new char[4096];
var buffer = ArrayPool<char>.Shared.Rent(4096);
try
{
cancellationToken.ThrowIfCancellationRequested();

cancellationToken.ThrowIfCancellationRequested();
int charsRead;
while ((charsRead = await reader.ReadAsync(buffer, 0, 4096).ConfigureAwait(false)) > 0)

@Tyrrrz Tyrrrz Feb 17, 2026

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Same here, it's okay if we read more bytes. Apply this logic in other relevant places

Copilot AI Feb 17, 2026

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done in a132bff - applied the same change to both ReadAllTextAsync overloads

{
cancellationToken.ThrowIfCancellationRequested();
content.Append(buffer, 0, charsRead);
}

int charsRead;
while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
return content.ToString();
}
finally
{
cancellationToken.ThrowIfCancellationRequested();
content.Append(buffer, 0, charsRead);
ArrayPool<char>.Shared.Return(buffer);
}

return content.ToString();
}

// https://learn.microsoft.com/dotnet/api/system.io.file.writeallbytesasync#system-io-file-writeallbytesasync(system-string-system-byte()-system-threading-cancellationtoken)
Expand Down