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tuned to avoid expensive biginteger operation (well, not "expensive", but a lot more expensive than a few shifts)

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when we need to debug, essentially assert the validity of the new tuned op, losing the performance benefit by duplicating the effort (to verify)
This commit is contained in:
jrandom
2004-05-18 18:33:37 +00:00
committed by zzz
parent 1a65d7061d
commit 9f17654052
1 changed files with 32 additions and 2 deletions
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34
core/java/src/net/i2p/data/UnsignedInteger.java
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@ -74,8 +74,36 @@ public class UnsignedInteger {
_log.error("Null data to be calculating for", new Exception("Argh"));
return 0;
} else if (data.length == 0) { return 0; }
BigInteger bi = new BigInteger(1, data);
return bi.longValue();
long rv = 0;
for (int i = 0; i < data.length; i++) {
long cur = (long)(data[i]&0xFF);
if (cur < 0) cur = cur+256;
cur = (cur << (8*(data.length-i-1)));
rv += cur;
}
// only fire up this expensive assert if we're worried about it
if (_log.shouldLog(Log.DEBUG)) {
BigInteger bi = new BigInteger(1, data);
long biVal = bi.longValue();
if (biVal != rv) {
_log.log(Log.CRIT, "ERR: " + bi.toString(2) + " /\t" + bi.toString(16) + " /\t" + bi.toString()
+ " != \n " + Long.toBinaryString(rv) + " /\t" + Long.toHexString(rv)
+ " /\t" + rv);
for (int i = 0; i < data.length; i++) {
long cur = (long)(data[i]&0xFF);
if (cur < 0) cur = cur+256;
long shiftBy = (8*(data.length-i-1));
long old = cur;
cur = (cur << shiftBy);
_log.log(Log.CRIT, "cur["+ i+"]=" + Long.toHexString(cur) + " data = "
+ Long.toHexString((data[i]&0xFF)) + " shiftBy: " + shiftBy
+ " old: " + Long.toHexString(old));
}
throw new RuntimeException("b0rked on " + bi.toString() + " / " + rv);
}
}
return rv;
}
/**
@ -196,6 +224,7 @@ public class UnsignedInteger {
}
public static void main(String args[]) {
try {
_log.debug("Testing 1024");
testNum(1024L);
_log.debug("Testing 1025");
@ -210,6 +239,7 @@ public class UnsignedInteger {
testNum(1024 * 1024 * 1024 * 4L + 1L);
_log.debug("Testing MaxLong");
testNum(Long.MAX_VALUE);
} catch (Throwable t) { t.printStackTrace(); }
try {
Thread.sleep(1000);
} catch (Throwable t) {