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Use Stream.CopyTo{Async} in NonCryptographicHashAlgorithm.Append{Async}#103669

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Merged

stephentoub merged 1 commit intodotnet:mainfromstephentoub:hashcopyto

Jun 19, 2024

Merged

Use Stream.CopyTo{Async} in NonCryptographicHashAlgorithm.Append{Async}#103669

stephentoub merged 1 commit intodotnet:mainfromstephentoub:hashcopyto

Jun 19, 2024

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stephentoub commentedJun 18, 2024•
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Rather than using a manual loop to copy data from a stream to a buffer, use theStream.CopyTo{Async} method. Downside is there's an extra 32 byte allocation for the temporary destination passthrough Stream object. Upside is it allows the source Stream's to optimize via its CopyTo{Async} override, e.g. MemoryStream.CopyTo just makes a single Write call with its buffer. The base Stream.CopyTo also uses a larger rented buffer size than these APIs were using.

Related to#103539

Before:

Method	Kind	Mean	Allocated
Hash	MemoryStream	79.76 us	568 B
Hash	FileStream	837.08 us	568 B

After:

Method	Kind	Mean	Allocated
Hash	MemoryStream	59.76 us	600 B
Hash	FileStream	131.51 us	600 B

usingBenchmarkDotNet.Attributes;usingBenchmarkDotNet.Running;usingSystem.IO.Hashing;usingSystem.Security.Cryptography;BenchmarkSwitcher.FromAssembly(typeof(Tests).Assembly).Run(args);[MemoryDiagnoser][HideColumns("Job","Error","StdDev","Median","RatioSD")]publicclassTests{privateStream_stream;privatebyte[]_bytes=RandomNumberGenerator.GetBytes(1024*1024);[Params("MemoryStream","FileStream")]publicstringKind{get;set;}[GlobalSetup]publicvoidSetup(){switch(Kind){case"MemoryStream":_stream=newMemoryStream(_bytes);break;case"FileStream":stringpath=Path.GetRandomFileName();File.WriteAllBytes(path,_bytes);_stream=newFileStream(path,FileMode.Open,FileAccess.Read,FileShare.Read,0,FileOptions.DeleteOnClose);break;}}[GlobalCleanup]publicvoidCleanup()=>_stream.Dispose();[Benchmark]publiculongHash(){_stream.Position=0;varhash=newXxHash3();hash.Append(_stream);returnhash.GetCurrentHashAsUInt64();}}