new stream Copy benchmark

Author: lainio

try/copy_test.go

@@ -3,6 +3,7 @@ package try_test
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"io"
 	"os"
 	"testing"
@@ -13,6 +14,19 @@ import (
 
 const dataFile = "./try.go"
 
+func Benchmark_CopyBufferMy(b *testing.B) {
+	all, err := os.ReadFile(dataFile)
+	test.Requiref(b, err == nil, "error: %v", err)
+	test.Require(b, all != nil)
+
+	buf := make([]byte, 4)
+	dst := bufio.NewWriter(bytes.NewBuffer(make([]byte, 0, len(all))))
+	src := bytes.NewReader(all)
+	for n := 0; n < b.N; n++ {
+		try.To1(myCopyBuffer(dst, src, buf))
+	}
+}
+
 func Benchmark_CopyBufferStd(b *testing.B) {
 	all, err := os.ReadFile(dataFile)
 	test.Requiref(b, err == nil, "error: %v", err)
@@ -40,3 +54,36 @@ func Benchmark_CopyBufferOur(b *testing.B) {
 		}
 	}
 }
+
+// myCopyBuffer is copy/paste from Go std lib to remove noice and measure only a
+// loop
+func myCopyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error) {
+	for {
+		nr, er := src.Read(buf)
+		if nr > 0 {
+			nw, ew := dst.Write(buf[0:nr])
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = errors.New("invalid write result")
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				err = er
+			}
+			break
+		}
+	}
+	return written, err
+}