SimpleDataStructure (I2P Anonymous Network - Java Documentation

java.lang.Object
- net.i2p.data.DataStructureImpl
- - net.i2p.data.SimpleDataStructure

All Implemented Interfaces:

Serializable, DataStructure

Direct Known Subclasses:

EncryptedBuildRecord, Hash, Hash384, Hash512, NodeInfo, PrivateKey, PublicKey, SessionKey, SessionTag, SHA1Hash, Signature, SigningPrivateKey, SigningPublicKey
```
public abstract class SimpleDataStructure
extends DataStructureImpl
```
A SimpleDataStructure contains only a single fixed-length byte array. The main reason to do this is to override toByteArray() and fromByteArray(), which are used by toBase64(), fromBase64(), and calculateHash() in DataStructureImpl - otherwise these would go through a wasteful array-to-stream-to-array pass. It also centralizes a lot of common code. Implemented in 0.8.2 and retrofitted over several of the classes in this package. As of 0.8.3, SDS objects may be cached. An SDS may be instantiated with null data, and setData(null) is also OK. However, once non-null data is set, the data reference is immutable; subsequent attempts to set the data via setData(), readBytes(), fromByteArray(), or fromBase64() will throw a RuntimeException.

Since:

0.8.2

Author:

zzz

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

protected byte[] _data

Fields
Modifier and Type	Field	Description
`protected byte[]`	`_data`

Constructor Summary

Constructors
Constructor Description

SimpleDataStructure()
A new instance with the data set to null.

SimpleDataStructure(byte[] data)

Constructors
Constructor	Description
`SimpleDataStructure()`	A new instance with the data set to null.
`SimpleDataStructure(byte[] data)`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`Hash`	`calculateHash()`	Calculate the SHA256 value of this object (useful for a few scenarios)
`boolean`	`equals(Object obj)`	Warning - this returns true for two different classes with the same size and same data, e.g.
`void`	`fromBase64(String data)`	Sets the data.
`void`	`fromByteArray(byte[] data)`	Overridden for efficiency.
`byte[]`	`getData()`	Get the data reference (not a copy)
`int`	`hashCode()`	We assume the data has enough randomness in it, so use the first 4 bytes for speed.
`abstract int`	`length()`	The legal length of the byte array in this data structure
`void`	`readBytes(InputStream in)`	Sets the data.
`void`	`setData(byte[] data)`	Sets the data.
`String`	`toBase64()`	render the structure into modified base 64 notation
`byte[]`	`toByteArray()`	Overridden for efficiency.
`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
read

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

- Field Detail
  - _data
```
protected byte[] _data
```
- Constructor Detail
  - SimpleDataStructure
```
public SimpleDataStructure()
```
    A new instance with the data set to null. Call readBytes(), setData(), or fromByteArray() after this to set the data
  - SimpleDataStructure
```
public SimpleDataStructure(byte[] data)
```
    Throws:
    
    IllegalArgumentException - if data is not the legal number of bytes (but null is ok)
- Method Detail
  - length
```
public abstract int length()
```
    The legal length of the byte array in this data structure
    
    Since:
    
    0.8.2
  - getData
```
public byte[] getData()
```
    Get the data reference (not a copy)
    
    Returns:
    
    the byte array, or null if unset
  - setData
```
public void setData(byte[] data)
```
    Sets the data.
    
    Parameters:
    
    data - of correct length, or null
    
    Throws:
    
    IllegalArgumentException - if data is not the legal number of bytes (but null is ok)
    
    RuntimeException - if data already set.
  - readBytes
```
public void readBytes(InputStream in)
               throws DataFormatException,
                      IOException
```
    Sets the data.
    
    Parameters:
    
    in - the stream to read
    
    Throws:
    
    RuntimeException - if data already set.
    
    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
  - 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
  - fromBase64
```
public void fromBase64(String data)
                throws DataFormatException
```
    Sets the data.
    
    Specified by:
    
    fromBase64 in interface DataStructure
    
    Overrides:
    
    fromBase64 in class DataStructureImpl
    
    Throws:
    
    DataFormatException - if decoded data is not the legal number of bytes or on decoding error
    
    RuntimeException - if data already set.
  - calculateHash
```
public Hash calculateHash()
```
    Description copied from interface: DataStructure
    
    Calculate the SHA256 value of this object (useful for a few scenarios)
    
    Specified by:
    
    calculateHash in interface DataStructure
    
    Overrides:
    
    calculateHash in class DataStructureImpl
    
    Returns:
    
    the SHA256 hash of the byte array, or null if the data is null
  - toByteArray
```
public byte[] toByteArray()
```
    Overridden for efficiency.
    
    Specified by:
    
    toByteArray in interface DataStructure
    
    Overrides:
    
    toByteArray in class DataStructureImpl
    
    Returns:
    
    same thing as getData()
  - fromByteArray
```
public void fromByteArray(byte[] data)
                   throws DataFormatException
```
    Overridden for efficiency. Does the same thing as setData() but null not allowed.
    
    Specified by:
    
    fromByteArray in interface DataStructure
    
    Overrides:
    
    fromByteArray in class DataStructureImpl
    
    Parameters:
    
    data - non-null
    
    Throws:
    
    DataFormatException - if null or wrong length
    
    RuntimeException - if data already set.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - hashCode
```
public int hashCode()
```
    We assume the data has enough randomness in it, so use the first 4 bytes for speed. If this is not the case, override in the extending class.
    
    Overrides:
    
    hashCode in class Object
  - equals
```
public boolean equals(Object obj)
```
    Warning - this returns true for two different classes with the same size and same data, e.g. SessionKey and SessionTag, but you wouldn't put them in the same Set, would you?
    
    Overrides:
    
    equals in class Object

Class SimpleDataStructure

Field Summary

Constructor Summary

Method Summary

Methods inherited from class net.i2p.data.DataStructureImpl

Methods inherited from class java.lang.Object

Field Detail

_data

Constructor Detail

SimpleDataStructure

SimpleDataStructure

Method Detail

length

getData

setData

readBytes

writeBytes

toBase64

fromBase64

calculateHash

toByteArray

fromByteArray

toString

hashCode

equals