buf := NewBuffer(make([]byte, n*utf8.UTFMax))
	for i := 0; i < b.N; i++ {
		buf.Reset()
		for i := 0; i < n; i++ {
			buf.WriteRune(r)
		}
	}
}

// From Issue 5154.
func BenchmarkBufferNotEmptyWriteRead(b *testing.B) {
	buf := make([]byte, 1024)
	for i := 0; i < b.N; i++ {
		var b Buffer
		b.Write(buf[0:1])
		for i := 0; i < 5<<10; i++ {
			b.Write(buf)
			b.Read(buf)
		}
	}
}