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Fix operator precedence bug in datagram ACK timeout calculation #309

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Merged
dpharris merged 1 commit into from
Sep 25, 2026
+25 −2
Merged

Fix operator precedence bug in datagram ACK timeout calculation #309

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11 changes: 9 additions & 2 deletions src/org/openlcb/implementations/MemoryConfigurationService.java
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Original file line number Diff line number Diff line change
Expand Up @@ -527,6 +527,14 @@ public void run() {
retryTimer.schedule(tt, timeout);
}

static int computeTimeout(int flags) {
int timeoutExp = flags & 0x0F;
if (timeoutExp == 0) {
return 3000; // no timeout specified, 3 seconds is default
}
return (1 << timeoutExp) * 1000; // 2^N seconds to msec
}

// invoked when retryTimer times out
private void timeoutRetry(final McsRequestMemo memo) {
logger.log(Level.FINE, "timeoutRetry entry");
Expand Down Expand Up @@ -556,8 +564,7 @@ public void handleSuccess(int flags) {
((flags & DatagramService.FLAG_REPLY_PENDING) != 0)) {
// Leave the memo in the pending, will wait for reply datagram.
logger.fine("rcvd RequestWithReplyDatagram with flags "+flags);
int timeout = 1 << (flags & 0x0F) * 1000; // to msec
if ((flags & 0x0F) == 0) timeout = 3000; // no timeout specified, 3 seconds is default
int timeout = computeTimeout(flags);
logger.fine(" and timeout "+timeout+", restarting");
restartTimeout(memo, timeout);
return;
Expand Down
16 changes: 16 additions & 0 deletions test/org/openlcb/implementations/MemoryConfigurationServiceTest.java
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Expand Up @@ -702,4 +702,20 @@ public void handleAddrSpaceData(NodeID dest, int space, long hiAddress, long low

}

@Test
public void testComputeTimeout() {
// Exponent 0: default 3000 ms
Assert.assertEquals(3000, MemoryConfigurationService.computeTimeout(0));
Assert.assertEquals(3000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 0));

// Exponents 1..4: 2^N seconds in milliseconds
Assert.assertEquals(2000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 1));
Assert.assertEquals(4000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 2));
Assert.assertEquals(8000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 3));
Assert.assertEquals(16000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 4));

// Max exponent 15: 2^15 seconds in milliseconds
Assert.assertEquals(32768000, MemoryConfigurationService.computeTimeout(DatagramService.FLAG_REPLY_PENDING | 15));
}

}
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