SHA1Hash

java.lang.Object

net.i2p.data.SimpleDataStructure

net.i2p.crypto.SHA1Hash

All Implemented Interfaces:: DataStructure

Direct Known Subclasses:: InfoHash, NID, TokenKey

public class SHA1Hashextends SimpleDataStructure

I2P data structure for SHA-1 hash values.

This class provides a SimpleDataStructure wrapper for 20-byte SHA-1 hashes used throughout I2P for data integrity and identification purposes. It extends SimpleDataStructure to support I2P's serialization framework and provides efficient caching of hash codes.

Common uses include:

Router and destination identifiers
Message integrity verification
Data structure indexing and lookup

Field Summary
Modifier and Type
Field
Description
private int
_cachedHashCode
Hash of the data, computed on demand and then kept.
static final int
HASH_LENGTH
Number of bytes in a SHA-1 hash.
Fields inherited from class SimpleDataStructure
_data
Modifier and Type
Field
Description
protected byte[]
_data
The byte array data for this structure.
Constructor Summary
Constructors
Constructor
Description
SHA1Hash()
Create an empty SHA-1 hash (data is null).
SHA1Hash(byte[] data)
Create a SHA-1 hash from the given data.
Method Summary
All Methods
Modifier and Type
Method
Description
int
hashCode()
A Hash is a hash, so just use the first 4 bytes for speed.
int
length()
Length of a SHA-1 hash.
void
readBytes(InputStream in)
Read the hash data from a stream.
void
setData(byte[] data)
IllegalArgumentException if data is not 20 bytes (null is ok).
Methods inherited from class SimpleDataStructure
calculateHash, equals, fromBase64, fromByteArray, getData, read, toBase64, toByteArray, toString, writeBytes
Modifier and Type
Method
Description
Hash
calculateHash()
SHA256 hash of the byte array, or null if data is null.
boolean
equals(Object obj)
Compares the raw data only: two different SimpleDataStructure subclasses of the same length holding the same bytes are equal, e.g.
void
fromBase64(String data)
Data from the base64 string.
void
fromByteArray(byte[] data)
Does the same thing as SimpleDataStructure.setData(byte[]) but null not allowed.
byte[]
getData()
Data reference (not a copy).
protected int
read(InputStream in, byte[] target)
Repeated reads until the buffer is full or IOException is thrown.
String
toBase64()
Renders the structure into modified base 64 notation.
byte[]
toByteArray()
Same thing as getData().
String
toString()
Returns a string representation of this data structure.
void
writeBytes(OutputStream out)
Writes the data to the output stream.
Methods inherited from class Object
clone, getClass, notify, notifyAll, wait, wait, wait

Field Details
- _cachedHashCode
  private int _cachedHashCode
  Hash of the data, computed on demand and then kept.
- HASH_LENGTH
  public static final int HASH_LENGTH
  Number of bytes in a SHA-1 hash.
  See Also:
  Constant Field Values
Constructor Details
- SHA1Hash
  public SHA1Hash()
  Create an empty SHA-1 hash (data is null).
- SHA1Hash
  public SHA1Hash(byte[] data)
  Create a SHA-1 hash from the given data.
  Parameters:
  data - the 20-byte SHA-1 hash data
  Throws:
  IllegalArgumentException - if data is not 20 bytes (null is ok)
Method Details
- length
  public int length()
  Length of a SHA-1 hash.
  Specified by:
  length in class SimpleDataStructure
  Returns:
  20, the hash length in bytes
- setData
  public void setData(byte[] data)
  IllegalArgumentException if data is not 20 bytes (null is ok).
  Overrides:
  setData in class SimpleDataStructure
  Parameters:
  data - of correct length, or null
  Throws:
  IllegalArgumentException - if data is not 20 bytes (null is ok)
- readBytes
  public void readBytes(InputStream in) throws DataFormatException, IOException
  Read the hash data from a stream.
  Specified by:
  readBytes in interface DataStructure
  Overrides:
  readBytes in class SimpleDataStructure
  Parameters:
  in - the stream to read
  Throws:
  DataFormatException - if the data is improperly formatted
  IOException - if there was a problem reading the stream
- hashCode
  public int hashCode()
  A Hash is a hash, so just use the first 4 bytes for speed.
  Overrides:
  hashCode in class SimpleDataStructure
  Returns:
  the hash code

Field Summary

Fields inherited from class SimpleDataStructure

Constructor Summary

Method Summary

Methods inherited from class SimpleDataStructure

Methods inherited from class Object

Field Details

_cachedHashCode

HASH_LENGTH

Constructor Details

SHA1Hash

Method Details

length

setData

readBytes

hashCode