buffer adapted from go/src/fmt/print.go
type Buffer []byte
func New() *Buffer
func (b *Buffer) Free()
func (b *Buffer) Len() int
func (b *Buffer) Reset()
func (b *Buffer) SetLen(n int)
func (b *Buffer) String() string
func (b *Buffer) Write(p []byte) (int, error)
func (b *Buffer) WriteByte(c byte) error
func (b *Buffer) WriteString(s string) (int, error)