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speed up XORComparators

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zzz
2013-06-21 15:13:37 +00:00
parent 1444f1239f
commit 322e76d2a9
2 changed files with 26 additions and 12 deletions
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19
apps/i2psnark/java/src/net/i2p/kademlia/XORComparator.java
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@ -2,7 +2,6 @@ package net.i2p.kademlia;
import java.util.Comparator; import java.util.Comparator;
import net.i2p.data.DataHelper;
import net.i2p.data.SimpleDataStructure; import net.i2p.data.SimpleDataStructure;
/** /**
@ -21,8 +20,20 @@ class XORComparator<T extends SimpleDataStructure> implements Comparator<T> {
} }
public int compare(T lhs, T rhs) { public int compare(T lhs, T rhs) {
byte lhsDelta[] = DataHelper.xor(lhs.getData(), _base); // same as the following but byte-by-byte for efficiency
byte rhsDelta[] = DataHelper.xor(rhs.getData(), _base); //byte lhsDelta[] = DataHelper.xor(lhs.getData(), _base);
return DataHelper.compareTo(lhsDelta, rhsDelta); //byte rhsDelta[] = DataHelper.xor(rhs.getData(), _base);
//return DataHelper.compareTo(lhsDelta, rhsDelta);
byte lhsb[] = lhs.getData();
byte rhsb[] = rhs.getData();
for (int i = 0; i < _base.length; i++) {
int ld = (lhsb[i] ^ _base[i]) & 0xff;
int rd = (rhsb[i] ^ _base[i]) & 0xff;
if (ld < rd)
return -1;
if (ld > rd)
return 1;
}
return 0;
} }
} }

19
router/java/src/net/i2p/router/networkdb/kademlia/XORComparator.java
View File

@ -2,32 +2,35 @@ package net.i2p.router.networkdb.kademlia;
import java.util.Comparator; import java.util.Comparator;
import net.i2p.data.DataHelper;
import net.i2p.data.Hash; import net.i2p.data.Hash;
/** /**
* Help sort Hashes in relation to a base key using the XOR metric. * Help sort Hashes in relation to a base key using the XOR metric.
* Warning - not thread safe.
*/ */
class XORComparator implements Comparator<Hash> { class XORComparator implements Comparator<Hash> {
private final byte[] _base; private final byte[] _base;
private final byte[] _lx, _rx;
/** /**
* @param target key to compare distances with * @param target key to compare distances with
*/ */
public XORComparator(Hash target) { public XORComparator(Hash target) {
_base = target.getData(); _base = target.getData();
_lx = new byte[Hash.HASH_LENGTH];
_rx = new byte[Hash.HASH_LENGTH];
} }
/** /**
* getData() of args must be non-null * getData() of args must be non-null
*/ */
public int compare(Hash lhs, Hash rhs) { public int compare(Hash lhs, Hash rhs) {
DataHelper.xor(lhs.getData(), 0, _base, 0, _lx, 0, Hash.HASH_LENGTH); byte lhsb[] = lhs.getData();
DataHelper.xor(rhs.getData(), 0, _base, 0, _rx, 0, Hash.HASH_LENGTH); byte rhsb[] = rhs.getData();
return DataHelper.compareTo(_lx, _rx); for (int i = 0; i < _base.length; i++) {
int ld = (lhsb[i] ^ _base[i]) & 0xff;
int rd = (rhsb[i] ^ _base[i]) & 0xff;
if (ld < rd)
return -1;
if (ld > rd)
return 1;
}
return 0;
} }
} }