Method SubBuf

util/buffer.go:190–192

(start int, length int)

	return cap(b)
}
func (b Buffer) SubBuf(start int, length int) Buffer {
	return b[start : start+length]
}

// Malloc 扩大原来的buffer的长度，返回新增的buffer
func (b *Buffer) Malloc(count int) Buffer {