FastI2NPMessageImpl

java.lang.Object

net.i2p.data.i2np.I2NPMessageImpl

net.i2p.data.i2np.FastI2NPMessageImpl

All Implemented Interfaces:: I2NPMessage

Direct Known Subclasses:: DatabaseLookupMessage, DatabaseSearchReplyMessage, DatabaseStoreMessage, DataMessage, DeliveryStatusMessage, GarlicMessage, TunnelDataMessage, TunnelGatewayMessage, UnknownI2NPMessage

public abstract class FastI2NPMessageImplextends I2NPMessageImpl

Ignore, but save, the SHA-256 checksum in the full 16-byte header when read in. Use the same checksum when writing out.

This is a savings for NTCP in, and for NTCP-in to NTCP-out for TunnelDataMessages. It's also a savings for messages embedded in other messages. Note that SSU does not use the SHA-256 checksum.

Subclasses must take care to set _hasChecksum to false to invalidate it if the message payload changes between reading and writing.

It isn't clear where, if anywhere, we actually need to send a checksum. For point-to-point messages over NTCP where we know the router version of the peer, we could add a method to skip checksum generation. For end-to-end I2NP messages embedded in a Garlic, TGM, etc... we would need a flag day.

Nested Class Summary
Nested classes/interfaces inherited from class I2NPMessageImpl
I2NPMessageImpl.Builder
Modifier and Type
Class
Description
static interface
I2NPMessageImpl.Builder
Interface for extending the types of messages handled - unused.
Field Summary
Fields
Modifier and Type
Field
Description
protected byte
_checksum
One-byte checksum.
protected boolean
_hasChecksum
Whether the message includes a checksum.
Fields inherited from class I2NPMessageImpl
_context, _expiration, _log, CHECKSUM_LENGTH, DEFAULT_EXPIRATION_MS, HEADER_LENGTH
Modifier and Type
Field
Description
protected final I2PAppContext
_context
Application context this message belongs to.
protected long
_expiration
Expiration time in milliseconds since the epoch, as an I2P Date.
protected final Log
_log
Log for the message class, taken from the context's log manager.
static final int
CHECKSUM_LENGTH
Number of checksum bytes the message header carries.
static final long
DEFAULT_EXPIRATION_MS
Default lifetime of an unsent message, one minute in milliseconds.
static final int
HEADER_LENGTH
I2NP message header size in bytes.
Fields inherited from interface I2NPMessage
MAX_ID_VALUE, MAX_SIZE
Modifier and Type
Field
Description
static final long
MAX_ID_VALUE
4 bytes unsigned.
static final int
MAX_SIZE
Nominal limit, actual max is much less.
Constructor Summary
Constructors
Constructor
Description
FastI2NPMessageImpl(I2PAppContext context)
Create a message that will carry the one-byte checksum of the fast (5 byte header) format.
Method Summary
Public Methods
Modifier and Type
Method
Description
int
readBytes(byte[] data, int type, int offset, int maxLen)
Ignore, but save, the checksum, to be used later if necessary.
int
toByteArray(byte[] buffer)
If available, use the previously-computed or previously-read checksum for speed.
protected int
toByteArrayWithSavedChecksum(byte[] buffer)
Use a previously-computed checksum for speed.
Methods inherited from class I2NPMessageImpl
calculateWrittenLength, createMessage, fromRawByteArray, fromRawByteArrayNTCP2, getMessageExpiration, getMessageSize, getRawMessageSize, getUniqueId, getUniqueId, readBytes, readMessage, setMessageExpiration, setUniqueId, toByteArray, toByteArray, toRawByteArray, toRawByteArrayNTCP2, writeMessageBody
Modifier and Type
Method
Description
protected abstract int
calculateWrittenLength()
Calculate the message body's length (not including the header and footer).
static I2NPMessage
createMessage(I2PAppContext context, int type)
Yes, this is fairly ugly, but its the only place it ever happens.
static I2NPMessage
fromRawByteArray(I2PAppContext ctx, byte[] buffer, int offset, int len, I2NPMessageHandler handler)
Read the message with a short 5-byte header.
static I2NPMessage
fromRawByteArrayNTCP2(I2PAppContext ctx, byte[] buffer, int offset, int len, I2NPMessageHandler handler)
Read the message with a short 9-byte header.
long
getMessageExpiration()
Date after which the message should be dropped (and the associated uniqueId forgotten).
int
getMessageSize()
Serialized message size, including the 16-byte header.
int
getRawMessageSize()
The raw header consists of a one-byte type and a 4-byte expiration in seconds only.
long
getUniqueId()
Unique id for this message, lazily initialized when negative.
long
getUniqueId(long msgIDBloomXor)
Replay resistant message Id.
int
readBytes(byte[] data, int type, int offset)
Read the header, then read the rest into buffer, then call readMessage in the implemented message type.
void
readMessage(byte[] data, int offset, int dataSize, int type, I2NPMessageHandler handler)
Read the message fields from the byte array, ignoring the handler.
void
setMessageExpiration(long exp)
The expiration is set to one minute from now in the constructor but it can be overridden here.
void
setUniqueId(long id)
The ID is set to a random value when written but it can be overridden here.
byte[]
toByteArray()
The message serialized into a new byte array.
int
toByteArray(byte[] buffer, int off)
Write the message to the buffer, returning the new offset (NOT the length).
int
toRawByteArray(byte[] buffer)
Write the message with a short 5-byte header.
int
toRawByteArrayNTCP2(byte[] buffer, int off)
Write the message to the buffer, returning the new offset (NOT the length).
protected abstract int
writeMessageBody(byte[] out, int curIndex)
Write the message body to the output array, starting at the given index.
Methods inherited from class Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface I2NPMessage
getType, readMessage
Modifier and Type
Method
Description
int
getType()
Return the unique identifier for this type of I2NP message, as defined in the I2NP spec.
void
readMessage(byte[] data, int offset, int dataSize, int type)
Read the body into the data structures, after the initial type byte and the uniqueId / expiration, using the current class's format as defined by the I2NP specification.

Field Details
- _checksum
  protected byte _checksum
  One-byte checksum.
- _hasChecksum
  protected boolean _hasChecksum
  Whether the message includes a checksum.
Constructor Details
- FastI2NPMessageImpl
  public FastI2NPMessageImpl(I2PAppContext context)
  Create a message that will carry the one-byte checksum of the fast (5 byte header) format.
  Parameters:
  context - the app context the parent uses for its RNG and properties
Method Details
- readBytes
  public int readBytes(byte[] data, int type, int offset, int maxLen) throws I2NPMessageException
  Ignore, but save, the checksum, to be used later if necessary.
  Specified by:
  readBytes in interface I2NPMessage
  Overrides:
  readBytes in class I2NPMessageImpl
  Parameters:
  data - the data, may or may not include the type
  type - the message type or -1 if we should read it here
  offset - where to start starting at type if type is < 0 (16 byte header) starting at ID if type is >= 0 (15 byte header)
  maxLen - read no more than this many bytes from data starting at offset, even if it is longer This includes the type byte only if type < 0
  Returns:
  total length of the message
  Throws:
  IllegalStateException - if called twice, to protect saved checksum
  I2NPMessageException - if there is no valid message
- toByteArray
  public int toByteArray(byte[] buffer)
  If available, use the previously-computed or previously-read checksum for speed.
  Specified by:
  toByteArray in interface I2NPMessage
  Overrides:
  toByteArray in class I2NPMessageImpl
  Parameters:
  buffer - the destination array, which must have room for I2NPMessage.getMessageSize() bytes
  Returns:
  the length written
- toByteArrayWithSavedChecksum
  protected int toByteArrayWithSavedChecksum(byte[] buffer)
  Use a previously-computed checksum for speed.
  Parameters:
  buffer - the destination array, must be at least I2NPMessageImpl.HEADER_LENGTH bytes long
  Returns:
  the number of bytes written into buffer

Nested Class Summary

Nested classes/interfaces inherited from class I2NPMessageImpl

Field Summary

Fields inherited from class I2NPMessageImpl

Fields inherited from interface I2NPMessage

Constructor Summary

Method Summary

Methods inherited from class I2NPMessageImpl

Methods inherited from class Object

Methods inherited from interface I2NPMessage

Field Details

_checksum

_hasChecksum

Constructor Details

Method Details

readBytes

toByteArray

toByteArrayWithSavedChecksum