io.go

// Copyright 2024 Rahim Afful-Brown. All Rights Reserved.
//
// Distributed under MIT license.
// See file LICENSE for detail or copy at https://opensource.org/licenses/MIT

package copy_test

import (
	"bufio"
	"io"
	"os"
	"testing"
)

func Benchmark_Copy(b *testing.B) {
	f := createFile(b)
	b.Run("CopyBuffer", func(b *testing.B) {
		for n := 0; n < b.N; n++ {
			b.StopTimer()
			f.Seek(0, io.SeekStart)
			src := &noopReader{f}
			dst := &noopWriter{io.Discard}
			buf := make([]byte, 5*1024*1024)
			b.StartTimer()
			io.CopyBuffer(dst, src, buf)
		}
	})
	b.Run("BufioWriter", func(b *testing.B) {
		for n := 0; n < b.N; n++ {
			b.StopTimer()
			f.Seek(0, io.SeekStart)
			src := &noopReader{f}
			dst := bufio.NewWriterSize(io.Discard, 5*1024*1024) // ReadFrom
			b.StartTimer()
			io.Copy(dst, src)
		}

	})
	b.Run("BufioReader", func(b *testing.B) {
		for n := 0; n < b.N; n++ {
			b.StopTimer()
			f.Seek(0, io.SeekStart)
			src := bufio.NewReaderSize(f, 5*1024*1024) // WriteTo
			dst := &noopWriter{io.Discard}
			b.StartTimer()
			io.Copy(dst, src)
		}
	})
}

func createFile(tb testing.TB) *os.File {
	tb.Helper()
	f, _ := os.CreateTemp(tb.TempDir(), "file-*.txt")
	for i := 0; i < 20*(1024*1024); i++ {
		f.Write([]byte("A"))
	}
	return f
}

type noopReader struct {
	w io.Reader
}

func (w *noopReader) Read(b []byte) (n int, err error) {
	return w.w.Read(b)
}

type noopWriter struct {
	w io.Writer
}

func (w *noopWriter) Write(b []byte) (n int, err error) {
	return w.w.Write(b)
}