## net.i2p.data
Class Hash

    java.lang.Object
      net.i2p.data.DataStructureImpl
          net.i2p.data.Hash

All Implemented Interfaces:
  DataStructure

Direct Known Subclasses:
  LocalHash

    public class Hash

extends DataStructureImpl

Defines the hash as defined by the I2P data structure spec. A hash is the SHA-256 of some data, taking up 32 bytes.

Author:
  jrandom

Field Summary
`static Hash` `FAKE_HASH`
`static int` `HASH_LENGTH`

Constructor Summary
`Hash()`
`Hash(byte[] data)`

Method Summary
`boolean` `equals(Object obj)`
`byte[]` `getData()`
`int` `hashCode()` a Hash is a hash, so just use the first 4 bytes for speed
`void` `readBytes(InputStream in)` Load up the current object with data from the given stream.
`void` `setData(byte[] data)`
`String` `toBase64()` render the structure into modified base 64 notation
`String` `toString()`
`void` `writeBytes(OutputStream out)` Write out the data structure to the stream, using the format defined in the I2P data structure specification.

Methods inherited from class net.i2p.data.DataStructureImpl
`calculateHash, fromBase64, fromByteArray, read, toByteArray`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### HASH_LENGTH

    public static final int HASH_LENGTH

See Also:
  Constant Field Values

### FAKE_HASH

    public static final Hash FAKE_HASH

Constructor Detail

### Hash

    public Hash()

### Hash

    public Hash(byte[] data)

Throws:
  `IllegalArgumentException` - if data is not 32 bytes (null is ok)

Method Detail

### getData

    public byte[] getData()

### setData

    public void setData(byte[] data)

  Throws:
    `IllegalArgumentException` - if data is not 32 bytes (null is ok)

### readBytes

    public void readBytes(InputStream in)
                   throws DataFormatException,
                          IOException

  Description copied from interface: `DataStructure`
  Load up the current object with data from the given stream. Data loaded this way must match the I2P data structure specification.

  Parameters:
    `in` - stream to read from
  Throws:
    `DataFormatException` - if the data is improperly formatted
    `IOException` - if there was a problem reading the stream

### writeBytes

    public void writeBytes(OutputStream out)
                    throws DataFormatException,
                           IOException

  Description copied from interface: `DataStructure`
  Write out the data structure to the stream, using the format defined in the I2P data structure specification.

  Parameters:
    `out` - stream to write to
  Throws:
    `DataFormatException` - if the data was incomplete or not yet ready to be written
    `IOException` - if there was a problem writing to the stream

### equals

    public boolean equals(Object obj)

  Overrides:
    `equals` in class `Object`

### hashCode

    public int hashCode()

  a Hash is a hash, so just use the first 4 bytes for speed

  Overrides:
    `hashCode` in class `Object`

### toString

    public String toString()

  Overrides:
    `toString` in class `Object`

### toBase64

    public String toBase64()

  Description copied from interface: `DataStructure`
  render the structure into modified base 64 notation

  Specified by:
    `toBase64` in interface `DataStructure`
  Overrides:
    `toBase64` in class `DataStructureImpl`
  Returns:
    null on error