Update Cursively benchmark code. (#1)

* Update Cursively benchmark code.
- VisitPartialFieldContents is required for correctness
- Use the original byte array, since we have one, instead of forcing a stream around it
- Set iteration time to 1 second, to work around dotnet/BenchmarkDotNet#837 while we wait for a version of this package that includes dotnet/BenchmarkDotNet#1573

* Change the order of this check

Whether or not this is the optimal order is almost certain to depend on the data: data sets that would almost never use the pool would likely hurt more by doing it this way, especially if this were a real-world application since this would likely push a line out of the CPU cache for no reason.

Then again, a real-world application probably wouldn't use the pool conditionally like this, so there's not much of a reason NOT to either.

Author: airbreather

benchmark.cmd

@@ -1,2 +1,2 @@
 dotnet build -c Release source/CsvBenchmark.sln
-bin\release\net5.0\CsvBenchmark.exe
+bin\release\net5.0\CsvBenchmark.exe --iterationTime 1000

source/CsvBenchmark/CsvReaderBenchmarks.cs

@@ -201,12 +201,29 @@ public void MgholamFastCSV()
 
 		class CursivelyStringVisitor : CsvReaderVisitorBase
 		{
+			readonly bool doPooling;
+			readonly byte[] bytes = new byte[1024];
+			int bytesUsed = 0;
+
 			// in any realistic scenario we'd need to at least know the column oridnal to do anything with the record
 			int ordinal = 0;
 
+			public CursivelyStringVisitor(bool doPooling)
+			{
+				this.doPooling = doPooling;
+			}
+
 			public override void VisitEndOfField(System.ReadOnlySpan<byte> chunk)
 			{
-				var str = Encoding.UTF8.GetString(chunk);
+				if (bytesUsed != 0)
+				{
+					chunk.CopyTo(bytes.AsSpan(bytesUsed, chunk.Length));
+					chunk = new ReadOnlySpan<byte>(bytes, 0, bytesUsed + chunk.Length);
+					bytesUsed = 0;
+				}
+				var str = doPooling && chunk.Length == 1 && chunk[0] < 128
+					? pool[chunk[0]]
+					: Encoding.UTF8.GetString(chunk);
 				ordinal++;
 			}
 
@@ -217,17 +234,20 @@ public override void VisitEndOfRecord()
 
 			public override void VisitPartialFieldContents(System.ReadOnlySpan<byte> chunk)
 			{
+				chunk.CopyTo(bytes.AsSpan(bytesUsed, chunk.Length));
+				bytesUsed += chunk.Length;
 			}
 		}
 
 		[Benchmark]
-		public void CursivelyCsv()
+		[Arguments(false)]
+		[Arguments(true)]
+		public void CursivelyCsv(bool doPooling)
 		{
-			var s = TestData.GetUtf8Stream();
-			var proc = new CursivelyStringVisitor();
+			var d = TestData.GetUtf8Array();
+			var proc = new CursivelyStringVisitor(doPooling);
 			CsvSyncInput
-				.ForStream(s)
-				.WithMinReadBufferByteCount(BufferSize)
+				.ForMemory(d)
 				.Process(proc);
 		}
 
@@ -352,6 +372,9 @@ public void NRecoSelect()
 
 		class CursivelySelectVisitor : CsvReaderVisitorBase
 		{
+			readonly byte[] bytes = new byte[1024];
+			int bytesUsed = 0;
+
 			int ordinal = 0;
 			int row = 0;
 
@@ -361,6 +384,12 @@ class CursivelySelectVisitor : CsvReaderVisitorBase
 
 			public override void VisitEndOfField(ReadOnlySpan<byte> chunk)
 			{
+				if (bytesUsed != 0)
+				{
+					chunk.CopyTo(bytes.AsSpan(bytesUsed, chunk.Length));
+					chunk = new ReadOnlySpan<byte>(bytes, 0, bytesUsed + chunk.Length);
+					bytesUsed = 0;
+				}
 				if (row != 0) // skip the header row
 				{
 					switch (ordinal)
@@ -398,17 +427,21 @@ public override void VisitEndOfRecord()
 
 			public override void VisitPartialFieldContents(System.ReadOnlySpan<byte> chunk)
 			{
+				if (row > 0)
+				{
+					chunk.CopyTo(bytes.AsSpan(bytesUsed, chunk.Length));
+					bytesUsed += chunk.Length;
+				}
 			}
 		}
 
 		[Benchmark]
 		public void CursivelyCsvSelect()
 		{
-			var s = TestData.GetUtf8Stream();
+			var d = TestData.GetUtf8Array();
 			var proc = new CursivelySelectVisitor();
 			CsvSyncInput
-				.ForStream(s)
-				.WithMinReadBufferByteCount(BufferSize)
+				.ForMemory(d)
 				.Process(proc);
 		}
 

source/CsvBenchmark/TestData.cs

@@ -112,6 +112,11 @@ public static Stream GetUtf8Stream()
 			return new MemoryStream(CachedUtfData);
 		}
 
+		public static ReadOnlyMemory<byte> GetUtf8Array()
+		{
+			return CachedUtfData;
+		}
+
 		public static DbDataReader GetData()
 		{