ctf: cache enums for non-overlapping values under 4096

Yields a major performance boost on wide enum systems.

Change-Id: Ic65433ee8f7165fc610312681553f355879f3e67
Signed-off-by: Matthew Khouzam <[email protected]>

Author: MatthewKhouzam

ctf/org.eclipse.tracecompass.ctf.core/src/org/eclipse/tracecompass/ctf/core/event/types/EnumDeclaration.java

@@ -46,6 +46,7 @@
  */
 public final class EnumDeclaration extends Declaration implements ISimpleDatatypeDeclaration {
 
+    private static final int CACHE_SIZE = 4096;
     /**
      * A pair of longs class
      *
@@ -111,6 +112,7 @@ public String toString() {
     private final Multimap<Pair, String> fEnumMap = LinkedHashMultimap.create();
     private final IntegerDeclaration fContainerType;
     private Pair fLastAdded = new Pair(-1, -1);
+    private @Nullable String[] fCache = new String[CACHE_SIZE];
 
     // ------------------------------------------------------------------------
     // Constructors
@@ -212,6 +214,18 @@ public boolean add(long low, long high, @Nullable String label) {
         if (high < low) {
             return false;
         }
+        if(low < 0 || low >= CACHE_SIZE-1 || high < 0 || high >= CACHE_SIZE-1) {
+            fCache = null;
+        }
+        for (int i = (int) low; i < high; i++) { // high is inclusive
+            if(fCache != null) {
+                if (fCache[i]== null) {
+                    fCache[i]= label;
+                } else {
+                    fCache = null;
+                }
+            }
+        }
         Pair key = new Pair(low, high);
         fEnumMap.put(key, label);
         fLastAdded = key;
@@ -241,6 +255,12 @@ public boolean add(@Nullable String label) {
      * @return the label of that value, can be null
      */
     public @Nullable String query(long value) {
+        if (fCache != null) {
+            if (value < 0 || value >= CACHE_SIZE) {
+                return null;
+            }
+            return fCache[(int) value];
+        }
         List<String> strValues = new ArrayList<>();
         fEnumMap.forEach((k, v) -> {
             if (value >= k.getFirst() && value <= k.getSecond()) {