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

Optimize large buffer allocations with ArrayPool #78

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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
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17 changes: 13 additions & 4 deletions PolyShim/Net100/Random.cs
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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;

Expand All @@ -17,11 +18,19 @@ internal static class MemberPolyfills_Net100_Random
// https://learn.microsoft.com/dotnet/api/system.random.gethexstring#system-random-gethexstring(system-int32-system-boolean)
public string GetHexString(int stringLength, bool lowercase = false)
{
var bytes = new byte[(stringLength + 1) / 2];
random.NextBytes(bytes);
var byteCount = (stringLength + 1) / 2;

@Tyrrrz Tyrrrz Feb 17, 2026

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This can be inlined?

var bytes = ArrayPool<byte>.Shared.Rent(byteCount);
try
{
random.NextBytes(bytes);

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

// https://learn.microsoft.com/dotnet/api/system.random.getstring
Expand Down
23 changes: 15 additions & 8 deletions PolyShim/Net50/Convert.cs
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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

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Let's rename this to var chars

Copilot AI Feb 17, 2026

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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
37 changes: 26 additions & 11 deletions PolyShim/Net60/Random.cs
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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;

file static class RandomEx
Expand All @@ -32,15 +33,22 @@ public long NextInt64(long minValue, long maxValue)

var range = (ulong)(maxValue - minValue);

ulong ulongRand;
do
var buffer = ArrayPool<byte>.Shared.Rent(8);
try
{
var buffer = new byte[8];
random.NextBytes(buffer);
ulongRand = BitConverter.ToUInt64(buffer, 0);
} while (ulongRand > ulong.MaxValue - (ulong.MaxValue % range + 1) % range);
ulong ulongRand;
do
{
random.NextBytes(buffer);
ulongRand = BitConverter.ToUInt64(buffer, 0);
} while (ulongRand > ulong.MaxValue - (ulong.MaxValue % range + 1) % range);

return (long)(ulongRand % range) + minValue;
return (long)(ulongRand % range) + minValue;
}
finally
{
ArrayPool<byte>.Shared.Return(buffer);
}
}

// https://learn.microsoft.com/dotnet/api/system.random.nextint64#system-random-nextint64(system-int64)
Expand All @@ -52,11 +60,18 @@ public long NextInt64(long minValue, long maxValue)
// https://learn.microsoft.com/dotnet/api/system.random.nextsingle
public float NextSingle()
{
var buffer = new byte[4];
random.NextBytes(buffer);
var uintValue = BitConverter.ToUInt32(buffer, 0);
var buffer = ArrayPool<byte>.Shared.Rent(4);
try
{
random.NextBytes(buffer);
var uintValue = BitConverter.ToUInt32(buffer, 0);

return (uintValue >> 8) * (1.0f / (1u << 24));
return (uintValue >> 8) * (1.0f / (1u << 24));
}
finally
{
ArrayPool<byte>.Shared.Return(buffer);
}
}

// https://learn.microsoft.com/dotnet/api/system.random.shared
Expand Down
29 changes: 18 additions & 11 deletions PolyShim/Net70/TextReader.cs
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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

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

Copilot AI Feb 17, 2026

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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
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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

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Can be inlined?

Copilot AI Feb 17, 2026

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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);

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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);

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}
}

// https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.getstring
Expand Down
20 changes: 14 additions & 6 deletions PolyShim/NetCore10/Stream.cs
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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

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Read up to buffer.Length

Copilot AI Feb 17, 2026

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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
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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

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

Copilot AI Feb 17, 2026

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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

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

Copilot AI Feb 17, 2026

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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
14 changes: 11 additions & 3 deletions PolyShim/NetCore20/RandomNumberGenerator.cs
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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;
using System.Security.Cryptography;

Expand All @@ -20,9 +21,16 @@ public void GetBytes(byte[] data, int offset, int count)
if (count == 0)
return;

var buffer = new byte[count];
rng.GetBytes(buffer);
Array.Copy(buffer, 0, data, offset, count);
var buffer = ArrayPool<byte>.Shared.Rent(count);
try
{
rng.GetBytes(buffer);
Array.Copy(buffer, 0, data, offset, count);
}
finally
{
ArrayPool<byte>.Shared.Return(buffer);
}
}

// https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.getnonzerobytes#system-security-cryptography-randomnumbergenerator-getnonzerobytes(system-byte())
Expand Down
14 changes: 11 additions & 3 deletions PolyShim/NetCore21/RandomNumberGenerator.cs
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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;
using System.Security.Cryptography;

Expand All @@ -20,9 +21,16 @@ public void GetBytes(Span<byte> data)
if (data.Length == 0)
return;

var buffer = new byte[data.Length];
rng.GetBytes(buffer);
buffer.CopyTo(data);
var buffer = ArrayPool<byte>.Shared.Rent(data.Length);
try
{
rng.GetBytes(buffer);
buffer.AsSpan(0, data.Length).CopyTo(data);
}
finally
{
ArrayPool<byte>.Shared.Return(buffer);
}
}

// https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.getnonzerobytes#system-security-cryptography-randomnumbergenerator-getnonzerobytes(system-span((system-byte)))
Expand Down
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