Fix: Address missing `sizeHint` in `BuffersExtensions` write logic by Plerx2493 · Pull Request #126776 · dotnet/runtime

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
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Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Plerx2493 · 2026-04-10T22:53:54Z

Refactor BuffersExtensions to improve memory allocation efficiency. This update ensures the IBufferWriter receives the correct sizeHint based on the provided span size during data write operations.

dotnet-policy-service · 2026-04-10T22:54:59Z

Tagging subscribers to this area: @dotnet/area-system-memory
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Refactors BuffersExtensions.Write to pass an explicit sizeHint to IBufferWriter<T>.GetSpan(...), improving allocation behavior by requesting spans sized to the data being written.

Changes:

Update initial Write path to call GetSpan(value.Length) instead of GetSpan().
Update multi-segment write loop to call GetSpan(input.Length) for remaining data rather than GetSpan().

Copilot · 2026-04-10T22:57:22Z

 public static void Write<T>(this IBufferWriter<T> writer, ReadOnlySpan<T> value)
 {
- Span<T> destination = writer.GetSpan();
+ Span<T> destination = writer.GetSpan(value.Length);

 // Fast path, try copying to the available memory directly


This change alters the observable behavior of Write for writers that allocate based on sizeHint (e.g., the existing TestBufferWriterMultiSegment in System.Memory tests). With GetSpan(value.Length) / GetSpan(input.Length), those tests will no longer write one byte per segment (they'll typically write the whole span in a single segment), so current assertions like Comitted.Count == 12 will fail. Please update/add tests to validate the new contract (that the sizeHint passed equals the remaining input length) rather than relying on the old sizeHint == 0 growth behavior.

Plerx2493 · 2026-04-10T23:31:55Z

As it seems i was confused by the naming of the parameter and this would be the wrong behaivior.

/// <param name="sizeHint">The minimum length of the returned <see cref="System.Span{T}" />. If 0, a non-empty buffer of arbitrary size is returned.</param>

Add sizeHint to GetSpan in BuffersExtensions
e3114ba

CopilotAI review requested due to automatic review settings April 10, 2026 22:53

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

CopilotAI review requested due to automatic review settings April 10, 2026 22:53

github-actionsBot added the area-System.Memory label Apr 10, 2026

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

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github-actionsBot added the area-System.Memory label Apr 10, 2026

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

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github-actionsBot added the area-System.Memory label Apr 10, 2026

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

CopilotAI review requested due to automatic review settings April 10, 2026 22:53

github-actionsBot added the area-System.Memory label Apr 10, 2026

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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Add sizeHint to GetSpan in BuffersExtensions
e3114ba

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WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706
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Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789
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