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package net.i2p.data.i2np;
/*
* free (adj.): unencumbered; not under the control of others
* Written by jrandom in 2003 and released into the public domain
* with no warranty of any kind, either expressed or implied.
* It probably won't make your computer catch on fire, or eat
* your children, but it might. Use at your own risk.
*
*/
import java.io.IOException;
import net.i2p.I2PAppContext;
import net.i2p.data.Base64;
import net.i2p.data.DataFormatException;
import net.i2p.data.DataHelper;
import net.i2p.util.HexDump;
import net.i2p.util.Log;
import net.i2p.util.SimpleByteCache;
/**
* 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.
*
* @since 0.8.12
*/
public abstract class FastI2NPMessageImpl extends I2NPMessageImpl {
protected byte _checksum;
// We skip the fiction that CHECKSUM_LENGTH will ever be anything but 1
protected boolean _hasChecksum;
public FastI2NPMessageImpl(I2PAppContext context) {
super(context);
}
/**
* Ignore, but save, the checksum, to be used later if necessary.
*
* @param 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
* @throws IllegalStateException if called twice, to protect saved checksum
*/
@Override
public int readBytes(byte data[], int type, int offset, int maxLen) throws I2NPMessageException {
if (_hasChecksum)
throw new IllegalStateException(getClass().getSimpleName() + " read twice");
int headerSize = HEADER_LENGTH;
if (type >= 0)
headerSize--;
if (maxLen < headerSize)
throw new I2NPMessageException("Payload is too short " + maxLen);
int cur = offset;
if (type < 0) {
type = data[cur] & 0xff;
cur++;
}
setUniqueId(DataHelper.fromLong(data, cur, 4));
cur += 4;
_expiration = DataHelper.fromLong(data, cur, DataHelper.DATE_LENGTH);
cur += DataHelper.DATE_LENGTH;
int size = (int)DataHelper.fromLong(data, cur, 2);
cur += 2;
_checksum = data[cur];
cur++;
if (cur + size > data.length || headerSize + size > maxLen)
throw new I2NPMessageException("Payload is too short ["
+ "data.len=" + data.length
+ "maxLen=" + maxLen
+ " offset=" + offset
+ " cur=" + cur
+ " wanted=" + size + "]: " + getClass().getSimpleName());
int sz = Math.min(size, maxLen - headerSize);
readMessage(data, cur, sz, type);
cur += sz;
_hasChecksum = true;
if (VERIFY_TEST && _log.shouldLog(Log.INFO))
_log.info("Ignored c/s " + getClass().getSimpleName());
return cur - offset;
}
/**
* This tests the reuse-checksum feature.
* The results are that mostly UnknownI2NPMessages (from inside a TGM),
* with a lot of DeliveryStatusMessages,
* and a few DatabaseLookupMessages that get reused.
* The last two are tiny, but the savings at the gateway should help.
*/
private static final boolean VERIFY_TEST = false;
/**
* If available, use the previously-computed or previously-read checksum for speed
*/
@Override
public int toByteArray(byte buffer[]) {
if (_hasChecksum)
return toByteArrayWithSavedChecksum(buffer);
if (VERIFY_TEST && _log.shouldLog(Log.INFO))
_log.info("Generating new c/s " + getClass().getSimpleName());
return super.toByteArray(buffer);
}
/**
* Use a previously-computed checksum for speed
*/
protected int toByteArrayWithSavedChecksum(byte buffer[]) {
try {
int writtenLen = writeMessageBody(buffer, HEADER_LENGTH);
if (VERIFY_TEST) {
byte[] h = SimpleByteCache.acquire(32);
_context.sha().calculateHash(buffer, HEADER_LENGTH, writtenLen - HEADER_LENGTH, h, 0);
if (h[0] != _checksum) {
_log.log(Log.CRIT, "Please report " + getClass().getSimpleName() +
" size " + writtenLen +
" saved c/s " + Integer.toHexString(_checksum & 0xff) +
" calc " + Integer.toHexString(h[0] & 0xff), new Exception());
_log.log(Log.CRIT, "DUMP:\n" + HexDump.dump(buffer, HEADER_LENGTH, writtenLen - HEADER_LENGTH));
_log.log(Log.CRIT, "RAW:\n" + Base64.encode(buffer, HEADER_LENGTH, writtenLen - HEADER_LENGTH));
_checksum = h[0];
} else if (_log.shouldLog(Log.INFO)) {
_log.info("Using saved c/s " + getClass().getSimpleName() + ' ' + _checksum);
}
SimpleByteCache.release(h);
}
int payloadLen = writtenLen - HEADER_LENGTH;
int off = 0;
buffer[off++] = (byte) getType();
DataHelper.toLong(buffer, off, 4, getUniqueId());
off += 4;
DataHelper.toLong(buffer, off, DataHelper.DATE_LENGTH, _expiration);
off += DataHelper.DATE_LENGTH;
DataHelper.toLong(buffer, off, 2, payloadLen);
off += 2;
buffer[off] = _checksum;
return writtenLen;
} catch (I2NPMessageException ime) {
_context.logManager().getLog(getClass()).log(Log.CRIT, "Error writing", ime);
throw new IllegalStateException("Unable to serialize the message " + getClass().getSimpleName(), ime);
}
}
}
