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25 
26 package javax.crypto;
27 
28 import java.security.*;
29 import java.security.spec.*;
30 
31 import java.nio.ByteBuffer;
32 
33 /**
34  * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
35  * for the <code>Mac</code> class.
36  * All the abstract methods in this class must be implemented by each
37  * cryptographic service provider who wishes to supply the implementation
38  * of a particular MAC algorithm.
39  *
40  * <p> Implementations are free to implement the Cloneable interface.
41  *
42  * @author Jan Luehe
43  *
44  * @since 1.4
45  */
46 
47 public abstract class MacSpi {
48 
49     /**
50      * Returns the length of the MAC in bytes.
51      *
52      * @return the MAC length in bytes.
53      */
engineGetMacLength()54     protected abstract int engineGetMacLength();
55 
56     /**
57      * Initializes the MAC with the given (secret) key and algorithm
58      * parameters.
59      *
60      * @param key the (secret) key.
61      * @param params the algorithm parameters.
62      *
63      * @exception InvalidKeyException if the given key is inappropriate for
64      * initializing this MAC.
65      * @exception InvalidAlgorithmParameterException if the given algorithm
66      * parameters are inappropriate for this MAC.
67      */
engineInit(Key key, AlgorithmParameterSpec params)68     protected abstract void engineInit(Key key,
69                                        AlgorithmParameterSpec params)
70         throws InvalidKeyException, InvalidAlgorithmParameterException ;
71 
72     /**
73      * Processes the given byte.
74      *
75      * @param input the input byte to be processed.
76      */
engineUpdate(byte input)77     protected abstract void engineUpdate(byte input);
78 
79     /**
80      * Processes the first <code>len</code> bytes in <code>input</code>,
81      * starting at <code>offset</code> inclusive.
82      *
83      * @param input the input buffer.
84      * @param offset the offset in <code>input</code> where the input starts.
85      * @param len the number of bytes to process.
86      */
engineUpdate(byte[] input, int offset, int len)87     protected abstract void engineUpdate(byte[] input, int offset, int len);
88 
89     /**
90      * Processes <code>input.remaining()</code> bytes in the ByteBuffer
91      * <code>input</code>, starting at <code>input.position()</code>.
92      * Upon return, the buffer's position will be equal to its limit;
93      * its limit will not have changed.
94      *
95      * <p>Subclasses should consider overriding this method if they can
96      * process ByteBuffers more efficiently than byte arrays.
97      *
98      * @param input the ByteBuffer
99      * @since 1.5
100      */
engineUpdate(ByteBuffer input)101     protected void engineUpdate(ByteBuffer input) {
102         if (input.hasRemaining() == false) {
103             return;
104         }
105         if (input.hasArray()) {
106             byte[] b = input.array();
107             int ofs = input.arrayOffset();
108             int pos = input.position();
109             int lim = input.limit();
110             engineUpdate(b, ofs + pos, lim - pos);
111             input.position(lim);
112         } else {
113             int len = input.remaining();
114             byte[] b = new byte[CipherSpi.getTempArraySize(len)];
115             while (len > 0) {
116                 int chunk = Math.min(len, b.length);
117                 input.get(b, 0, chunk);
118                 engineUpdate(b, 0, chunk);
119                 len -= chunk;
120             }
121         }
122     }
123 
124     /**
125      * Completes the MAC computation and resets the MAC for further use,
126      * maintaining the secret key that the MAC was initialized with.
127      *
128      * @return the MAC result.
129      */
engineDoFinal()130     protected abstract byte[] engineDoFinal();
131 
132     /**
133      * Resets the MAC for further use, maintaining the secret key that the
134      * MAC was initialized with.
135      */
engineReset()136     protected abstract void engineReset();
137 
138     /**
139      * Returns a clone if the implementation is cloneable.
140      *
141      * @return a clone if the implementation is cloneable.
142      *
143      * @exception CloneNotSupportedException if this is called
144      * on an implementation that does not support <code>Cloneable</code>.
145      */
clone()146     public Object clone() throws CloneNotSupportedException {
147         if (this instanceof Cloneable) {
148             return super.clone();
149         } else {
150             throw new CloneNotSupportedException();
151         }
152     }
153 }
154