Fastest way to make a *byte.Buffer from a string

bufferstringwriter_test.go

package main

import (
	"bytes"
	"math/rand"
	"testing"
)

// go test -v -bench=. -benchtime=10s
//
// Benchmark_NewBuffer20	     1000000000	        16.8 ns/op	       0 B/op	       0 allocs/op
// Benchmark_NewBuffer1000	     1000000000	        16.3 ns/op	       0 B/op	       0 allocs/op
// Benchmark_NewString20	     100000000	       157 ns/op	      32 B/op	       1 allocs/op
// Benchmark_NewString1000	     10000000	      2161 ns/op	    1024 B/op	       1 allocs/op
// Benchmark_Write20	             50000000	       344 ns/op	     112 B/op	       1 allocs/op
// Benchmark_Write1000	             5000000	      3106 ns/op	    1136 B/op	       2 allocs/op
// Benchmark_WriteString20	     50000000	       346 ns/op	     112 B/op	       1 allocs/op
// Benchmark_WriteString1000	     5000000	      3049 ns/op	    1136 B/op	       2 allocs/op

var seq20, seq1000 string

func init() {
	seq20 = randSeq(20)
	seq1000 = randSeq(1000)
}

func Benchmark_NewBuffer20(b *testing.B) {
	data := []byte(seq20)
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_ = bytes.NewBuffer(data)
	}
}

func Benchmark_NewBuffer1000(b *testing.B) {
	data := []byte(seq1000)
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_ = bytes.NewBuffer(data)
	}
}

func Benchmark_NewString20(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_ = bytes.NewBufferString(seq20)
	}
}

func Benchmark_NewString1000(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_ = bytes.NewBufferString(seq1000)
	}
}

func Benchmark_Write20(b *testing.B) {
	data := []byte(seq20)
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, _ = bytes.NewBuffer(nil).Write(data)
	}
}

func Benchmark_Write1000(b *testing.B) {
	data := []byte(seq1000)
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, _ = bytes.NewBuffer(nil).Write(data)
	}
}

func Benchmark_WriteString20(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, _ = bytes.NewBuffer(nil).WriteString(seq20)
	}
}

func Benchmark_WriteString1000(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, _ = bytes.NewBuffer(nil).WriteString(seq1000)
	}
}

var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

func randSeq(n int) string {
	b := make([]rune, n)
	for i := range b {
		b[i] = letters[rand.Intn(len(letters))]
	}
	return string(b)
}