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7051206: JSR 292 method name SwitchPoint.isValid is misleading to unwary users; should be hasBeenInvalidated

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Reviewed-by: kvn, never, ysr
This commit is contained in:
John R Rose 2011-06-03 11:20:20 -07:00
parent c0d9c39aa2
commit ad33af1a1c
2 changed files with 26 additions and 12 deletions
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34
jdk/src/share/classes/java/lang/invoke/SwitchPoint.java
View File

@ -59,14 +59,14 @@ package java.lang.invoke;
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 @@ public class SwitchPoint {
}
/**
* 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);
}
/**

4
jdk/test/java/lang/invoke/JavaDocExamplesTest.java
View File

@ -477,14 +477,14 @@ assertEquals("Wilma, dear?", (String) worker2.invokeExact());
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"));
{}
}}