7051206: JSR 292 method name SwitchPoint.isValid is misleading to unwary users; should be hasBeenInvalidated
Reviewed-by: kvn, never, ysr
--- a/jdk/src/share/classes/java/lang/invoke/SwitchPoint.java Wed Jun 01 23:56:51 2011 -0700
+++ b/jdk/src/share/classes/java/lang/invoke/SwitchPoint.java Fri Jun 03 11:20:20 2011 -0700
@@ -59,14 +59,14 @@
MethodHandle MH_strcat = MethodHandles.lookup()
.findVirtual(String.class, "concat", MethodType.methodType(String.class, String.class));
SwitchPoint spt = new SwitchPoint();
-assert(spt.isValid());
+assert(!spt.hasBeenInvalidated());
// the following steps may be repeated to re-use the same switch point:
MethodHandle worker1 = MH_strcat;
MethodHandle worker2 = MethodHandles.permuteArguments(MH_strcat, MH_strcat.type(), 1, 0);
MethodHandle worker = spt.guardWithTest(worker1, worker2);
assertEquals("method", (String) worker.invokeExact("met", "hod"));
SwitchPoint.invalidateAll(new SwitchPoint[]{ spt });
-assert(!spt.isValid());
+assert(spt.hasBeenInvalidated());
assertEquals("hodmet", (String) worker.invokeExact("met", "hod"));
* </pre></blockquote>
* <p style="font-size:smaller;">
@@ -126,16 +126,30 @@
}
/**
- * Determines if this switch point is still valid.
- * <p>
+ * Determines if this switch point has been invalidated yet.
+ *
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * Because of the one-way nature of invalidation, once a switch point begins
+ * to return true for {@code hasBeenInvalidated},
+ * it will always do so in the future.
+ * On the other hand, a valid switch point visible to other threads may
+ * invalidated at any moment, due to a request by another thread.
+ * <p style="font-size:smaller;">
* Since invalidation is a global and immediate operation,
- * this query must be sequenced with any
- * other threads that could invalidate this switch point.
- * It may therefore be expensive.
- * @return true if this switch point has never been invalidated
+ * the execution of this query, on a valid switchpoint,
+ * must be internally sequenced with any
+ * other threads that could cause invalidation.
+ * This query may therefore be expensive.
+ * The recommended way to build a boolean-valued method handle
+ * which queries the invalidation state of a switch point {@code s} is
+ * to call {@code s.guardWithTest} on
+ * {@link MethodHandles#constant constant} true and false method handles.
+ *
+ * @return true if this switch point has been invalidated
*/
- public boolean isValid() {
- return (mcs.getTarget() == K_true);
+ public boolean hasBeenInvalidated() {
+ return (mcs.getTarget() != K_true);
}
/**
--- a/jdk/test/java/lang/invoke/JavaDocExamplesTest.java Wed Jun 01 23:56:51 2011 -0700
+++ b/jdk/test/java/lang/invoke/JavaDocExamplesTest.java Fri Jun 03 11:20:20 2011 -0700
@@ -477,14 +477,14 @@
MethodHandle MH_strcat = MethodHandles.lookup()
.findVirtual(String.class, "concat", MethodType.methodType(String.class, String.class));
SwitchPoint spt = new SwitchPoint();
-assert(spt.isValid());
+assert(!spt.hasBeenInvalidated());
// the following steps may be repeated to re-use the same switch point:
MethodHandle worker1 = MH_strcat;
MethodHandle worker2 = MethodHandles.permuteArguments(MH_strcat, MH_strcat.type(), 1, 0);
MethodHandle worker = spt.guardWithTest(worker1, worker2);
assertEquals("method", (String) worker.invokeExact("met", "hod"));
SwitchPoint.invalidateAll(new SwitchPoint[]{ spt });
-assert(!spt.isValid());
+assert(spt.hasBeenInvalidated());
assertEquals("hodmet", (String) worker.invokeExact("met", "hod"));
{}
}}