tmf: Bug 581427: handle BIG_BANG/BIG_CRUNCH in TmfTimestamp#getDelta

TmfTimestamp.BIG_CRUNCH.getDelta(TmfTimestamp.BIG_BANG) leads to an
invalid result due to an overflow.

Time deltas involving any of those two special values are defined as:

  BIG_BANG   - BIG_BANG   == ZERO
  BIG_CRUNCH - BIG_CRUNCH == ZERO

  BIG_BANG   - <anything other than BIG_BANG>   == BIG_BANG
  BIG_CRUNCH - <anything other than BIG_CRUNCH> == BIG_CRUNCH

  <anything other than BIG_BANG> - BIG_BANG     == BIG_CRUNCH
  <anything other than BIG_CRUNCH> - BIG_CRUNCH == BIG_BANG

Also, add tests to cover this.

Bug 581427

Change-Id: Ibb71126af0fee338c74791ed0e4ac8bd5cb87de6
Signed-off-by: Christophe Bedard <bedard.christophe@gmail.com>
Signed-off-by: Christophe Bedard <christophe.bedard@apex.ai>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass/org.eclipse.tracecompass/+/199616
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>

tmf/org.eclipse.tracecompass.tmf.core.tests/src/org/eclipse/tracecompass/tmf/core/tests/event/TmfTimestampDeltaTest.java

@@ -117,4 +117,12 @@ public void testToStringFormat() {
         assertEquals("toString", "06:55:00.000 000 000", ts3.toString(format));
         assertEquals("toString", "-00:00:00.123 450 000", ts4.toString(format));
     }
+
+    @Test
+    public void testToStringBigBangBigCrunch() {
+        ITmfTimestamp bang = new TmfTimestampDelta(TmfTimestamp.BIG_BANG);
+        ITmfTimestamp crunch = new TmfTimestampDelta(TmfTimestamp.BIG_CRUNCH);
+        assertEquals("toString", "-9223372036.854 775 808", bang.toString());
+        assertEquals("toString", "9223372036.854 775 807", crunch.toString());
+    }
 }

tmf/org.eclipse.tracecompass.tmf.core.tests/src/org/eclipse/tracecompass/tmf/core/tests/event/TmfTimestampTest.java

@@ -234,6 +234,14 @@ public void testToStringInterval() {
         assertEquals("toString", "-000.000 012 345", ts9.toString(TmfTimestampFormat.getDefaulIntervalFormat()));
     }
 
+    @Test
+    public void testToStringBigBangBigCrunch() {
+        ITmfTimestamp bang = TmfTimestamp.BIG_BANG;
+        ITmfTimestamp crunch = TmfTimestamp.BIG_CRUNCH;
+        assertEquals("toString", "-9223372036.854 775 808", bang.toString(TmfTimestampFormat.getDefaulIntervalFormat()));
+        assertEquals("toString", "9223372036.854 775 807", crunch.toString(TmfTimestampFormat.getDefaulIntervalFormat()));
+    }
+
     // ------------------------------------------------------------------------
     // normalize
     // ------------------------------------------------------------------------
@@ -694,6 +702,25 @@ public void testDelta() {
         exp = TmfTimestamp.create(4, 9);
         delta = t0.getDelta(t1);
         assertEquals("getDelta", 0, delta.compareTo(exp));
+
+        // Delta for BIG_CRUNCH and BIG_BANG
+        ITmfTimestamp bang = TmfTimestamp.BIG_BANG;
+        ITmfTimestamp crunch = TmfTimestamp.BIG_CRUNCH;
+        ITmfTimestamp zero = TmfTimestamp.ZERO;
+        ITmfTimestamp anyT = TmfTimestamp.create(1, 10);
+        ITmfTimestamp anyTN = TmfTimestamp.create(-2, 10);
+        assertEquals(bang.getDelta(bang), zero);
+        assertEquals(crunch.getDelta(crunch), zero);
+        assertEquals(crunch.getDelta(bang), crunch);
+        assertEquals(bang.getDelta(crunch), bang);
+        assertEquals(bang.getDelta(anyT), bang);
+        assertEquals(crunch.getDelta(anyT), crunch);
+        assertEquals(bang.getDelta(anyTN), bang);
+        assertEquals(crunch.getDelta(anyTN), crunch);
+        assertEquals(anyT.getDelta(bang), crunch);
+        assertEquals(anyT.getDelta(crunch), bang);
+        assertEquals(anyTN.getDelta(bang), crunch);
+        assertEquals(anyTN.getDelta(crunch), bang);
     }
 
 }

tmf/org.eclipse.tracecompass.tmf.core/src/org/eclipse/tracecompass/tmf/core/timestamp/TmfTimestamp.java

@@ -358,6 +358,40 @@ public ITmfTimestamp normalize(final long offset, final int scale) {
 
     @Override
     public ITmfTimestamp getDelta(final ITmfTimestamp ts) {
+        /**
+         * Some of the special instances of TmfTimestamp have a special meaning,
+         * so the delta between them and other values can be defined as:
+         *
+         * <pre>
+         * BIG_BANG   - BIG_BANG   == ZERO
+         * BIG_CRUNCH - BIG_CRUNCH == ZERO
+         *
+         * BIG_BANG   - <anything other than BIG_BANG>   == BIG_BANG
+         * BIG_CRUNCH - <anything other than BIG_CRUNCH> == BIG_CRUNCH
+         *
+         * <anything other than BIG_BANG> - BIG_BANG     == BIG_CRUNCH
+         * <anything other than BIG_CRUNCH> - BIG_CRUNCH == BIG_BANG
+         * </pre>
+         */
+        if (equals(BIG_BANG)) {
+            if (ts.equals(BIG_BANG)) {
+                return ZERO;
+            }
+            return BIG_BANG;
+        }
+        if (equals(BIG_CRUNCH)) {
+            if (ts.equals(BIG_CRUNCH)) {
+                return ZERO;
+            }
+            return BIG_CRUNCH;
+        }
+        if (ts.equals(BIG_BANG)) {
+            return BIG_CRUNCH;
+        }
+        if (ts.equals(BIG_CRUNCH)) {
+            return BIG_BANG;
+        }
+
         final int scale = getScale();
         final ITmfTimestamp nts = ts.normalize(0, scale);
         final long value = getValue() - nts.getValue();

tmf/org.eclipse.tracecompass.tmf.core/src/org/eclipse/tracecompass/tmf/core/timestamp/TmfTimestampDelta.java

@@ -101,7 +101,7 @@ public String toString() {
 
     @Override
     public String toString(TmfTimestampFormat format) {
-        if (getValue() < 0) {
+        if (getValue() < 0 && !equals(BIG_BANG)) {
             TmfTimestampDelta tmpTs = new TmfTimestampDelta(-getValue(), getScale());
             return "-" + tmpTs.toString(format); //$NON-NLS-1$
         }