用go实现cfb1模式

```go package cfb1 import ( "crypto/cipher" "errors" ) // NewCFB1 returns a stream cipher that implements CFB-1 mode. The key argument should be the AES key, either 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256. func NewCFB1(key []byte) (cipher.Stream, error) { // check key length is valid for AES encryption algorithm if len(key) != 16 && len(key) != 24 && len(key) != 32 { // not valid key length for AES encryption algorithm return nil, errors.New("invalid key size") // return an error if invalid key length is provided } else { // valid key length for AES encryption algorithm // create a new instance of cfb1 struct and return it as type of cipher.Stream interface return &cfb1{aesCipher: newAESCipher(key), blockSize: aesBlockSize}, nil // return new instance of cfb1 struct as type of cipher.Stream interface if valid key length is provided } } // cfb1 struct implements the cipher.Stream interface type cfb1 struct { aesCipher *aesCipher blockSize int } func (c *cfb1) XORKeyStream(dst, src []byte) { for i := 0; i < len(src); i += c.blockSize { var block [16]byte copy(block[:], src[i:i+c.blockSize]) c.aesCipher.Encrypt(&block) xorBytes(&dst[i], &src[i], &block[0], c.blockSize) } }