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Avoid temporary List allocation with HTTP/3 trailers #122677

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Merged
MihaZupan merged 2 commits into from
Jan 5, 2026
Merged

Avoid temporary List allocation with HTTP/3 trailers #122677

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afe4e0b
Avoid temporary List allocation with HTTP/3 trailers
MihaZupan Dec 20, 2025
483ca36
Merge branch 'main' into http-http3trailerlist
MihaZupan Jan 5, 2026
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14 changes: 5 additions & 9 deletions src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http3RequestStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ internal sealed class Http3RequestStream : IHttpStreamHeadersHandler, IAsyncDisp
private string[] _headerValues = Array.Empty<string>();

/// <summary>Any trailing headers.</summary>
private List<(HeaderDescriptor name, string value)>? _trailingHeaders;
private HttpResponseHeaders? _trailingHeaders;

// When reading response content, keep track of the number of bytes left in the current data frame.
private long _responseDataPayloadRemaining;
Expand Down Expand Up @@ -632,7 +632,7 @@ private async ValueTask DrainContentLength0Frames(CancellationToken cancellation

private async ValueTask ProcessTrailersAsync(long payloadLength, CancellationToken cancellationToken)
{
_trailingHeaders = new List<(HeaderDescriptor name, string value)>();
_trailingHeaders = new HttpResponseHeaders(containsTrailingHeaders: true);
await ReadHeadersAsync(payloadLength, cancellationToken).ConfigureAwait(false);

// In typical cases, there should be no more frames. Make sure to read the EOS.
Expand All @@ -651,13 +651,9 @@ private async ValueTask ProcessTrailersAsync(long payloadLength, CancellationTok

private void CopyTrailersToResponseMessage(HttpResponseMessage responseMessage)
{
if (_trailingHeaders?.Count > 0)
if (_trailingHeaders is not null)
{
foreach ((HeaderDescriptor name, string value) in _trailingHeaders)
{
responseMessage.TrailingHeaders.TryAddWithoutValidation(name, value);
}
_trailingHeaders.Clear();
responseMessage.StoreReceivedTrailingHeaders(_trailingHeaders);
}
}

Expand Down Expand Up @@ -1156,7 +1152,7 @@ int ParseStatusCode(int? index, string value)
_response!.Headers.TryAddWithoutValidation(descriptor.HeaderType.HasFlag(HttpHeaderType.Request) ? descriptor.AsCustomHeader() : descriptor, headerValue);
break;
case HeaderState.TrailingHeaders:
_trailingHeaders!.Add((descriptor.HeaderType.HasFlag(HttpHeaderType.Request) ? descriptor.AsCustomHeader() : descriptor, headerValue));
_trailingHeaders!.TryAddWithoutValidation(descriptor.HeaderType.HasFlag(HttpHeaderType.Request) ? descriptor.AsCustomHeader() : descriptor, headerValue);
break;
default:
Debug.Fail($"Unexpected {nameof(Http3RequestStream)}.{nameof(_headerState)} '{_headerState}'.");
Expand Down
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