storage [streamBufferSize]byte // array backing buffer slice
}

// NewCTR returns a Stream which encrypts/decrypts using the AES block
// cipher in counter mode. The length of iv must be the same as [BlockSize].
func (c *aesCipherAsm) NewCTR(iv []byte) cipher.Stream {
	if len(iv) != BlockSize {
		panic("cipher.NewCTR: IV length must equal block size")
	}
	var ac aesctr
	ac.block = c