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## javax.crypto
Class MacSpi

    java.lang.Object
      javax.crypto.MacSpi

    public abstract class MacSpi

extends Object

This class defines the Service Provider Interface (SPI) for the `Mac` class. All the abstract methods in this class must be implemented by each cryptographic service provider who wishes to supply the implementation of a particular MAC algorithm.

Implementations are free to implement the Cloneable interface.

Since:
  1.4

Constructor Summary
`MacSpi()`

Method Summary
`Object` | `clone()` Returns a clone if the implementation is cloneable.
`protected abstract byte[]` | `engineDoFinal()` Completes the MAC computation and resets the MAC for further use, maintaining the secret key that the MAC was initialized with.
`protected abstract int` | `engineGetMacLength()` Returns the length of the MAC in bytes.
`protected abstract void` | `engineInit(Key key, AlgorithmParameterSpec params)` Initializes the MAC with the given (secret) key and algorithm parameters.
`protected abstract void` | `engineReset()` Resets the MAC for further use, maintaining the secret key that the MAC was initialized with.
`protected abstract void` | `engineUpdate(byte input)` Processes the given byte.
`protected abstract void` | `engineUpdate(byte[] input, int offset, int len)` Processes the first `len` bytes in `input`, starting at `offset` inclusive.
`protected void` | `engineUpdate(java.nio.ByteBuffer input)` Processes `input.remaining()` bytes in the ByteBuffer `input`, starting at `input.position()`.

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### MacSpi

    public MacSpi()

Method Detail

### engineGetMacLength

    protected abstract int engineGetMacLength()

  Returns the length of the MAC in bytes.

  Returns:
    the MAC length in bytes.

### engineInit

    protected abstract void engineInit(Key key,
                                       AlgorithmParameterSpec params)
                                throws InvalidKeyException,
                                       InvalidAlgorithmParameterException

  Initializes the MAC with the given (secret) key and algorithm parameters.

  Parameters:
    `key` - the (secret) key.
    `params` - the algorithm parameters.
  Throws:
    `InvalidKeyException` - if the given key is inappropriate for initializing this MAC.
    `InvalidAlgorithmParameterException` - if the given algorithm parameters are inappropriate for this MAC.

### engineUpdate

    protected abstract void engineUpdate(byte input)

  Processes the given byte.

  Parameters:
    `input` - the input byte to be processed.

### engineUpdate

    protected abstract void engineUpdate(byte[] input,
                                         int offset,
                                         int len)

  Processes the first `len` bytes in `input`, starting at `offset` inclusive.

  Parameters:
    `input` - the input buffer.
    `offset` - the offset in `input` where the input starts.
    `len` - the number of bytes to process.

### engineUpdate

    protected void engineUpdate(java.nio.ByteBuffer input)

  Processes `input.remaining()` bytes in the ByteBuffer `input`, starting at `input.position()`. Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

  Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.

  Parameters:
    `input` - the ByteBuffer
  Since:
    1.5

### engineDoFinal

    protected abstract byte[] engineDoFinal()

  Completes the MAC computation and resets the MAC for further use, maintaining the secret key that the MAC was initialized with.

  Returns:
    the MAC result.

### engineReset

    protected abstract void engineReset()

  Resets the MAC for further use, maintaining the secret key that the MAC was initialized with.

### clone

    public Object clone()
                 throws CloneNotSupportedException

  Returns a clone if the implementation is cloneable.

  Overrides:
    `clone` in class `Object`
  Returns:
    a clone if the implementation is cloneable.
  Throws:
    `CloneNotSupportedException` - if this is called on an implementation that does not support `Cloneable`.

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