code: func NewLookAheadBufferUsing(src io.Reader, rawBuffer []byte) *LookAheadBuffer {
  	return &LookAheadBuffer{
  		src:           src,
  		buffer:        rawBuffer,
  		bytesBuffered: 0,
  	}
  }
docs: // NewLookAheadBufferUsing returns a new LookAheadBuffer which uses the
  // provided buffer as its raw buffer.  This allows buffer reuse, which reduces
  // unnecessary memory allocation.