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LUCENE-6989: Make casting to Runnable interface in cleaner hack easier to understand

This commit is contained in:
Uwe Schindler 2016-02-20 01:05:45 +01:00
parent 9418369b46
commit 0f29b3ec7f
1 changed files with 12 additions and 9 deletions
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21
lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java
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@ -343,8 +343,8 @@ public class MMapDirectory extends FSDirectory {
final Method m = directBufferClass.getMethod("cleaner");
m.setAccessible(true);
final MethodHandle directBufferCleanerMethod = lookup.unreflect(m);
final Class<?> cleanerClass = directBufferCleanerMethod.type().returnType();
MethodHandle directBufferCleanerMethod = lookup.unreflect(m);
Class<?> cleanerClass = directBufferCleanerMethod.type().returnType();
final MethodHandle cleanMethod;
if (Runnable.class.isAssignableFrom(cleanerClass)) {
@ -353,19 +353,22 @@ public class MMapDirectory extends FSDirectory {
if (sm != null) {
sm.checkPackageAccess("jdk.internal.ref");
}
cleanMethod = explicitCastArguments(lookup.findVirtual(Runnable.class, "run", methodType(void.class)),
methodType(void.class, cleanerClass));
// cast return value of cleaner() to Runnable:
directBufferCleanerMethod = directBufferCleanerMethod.asType(directBufferCleanerMethod.type().changeReturnType(Runnable.class));
cleanerClass = Runnable.class;
// lookup run() method on the interface instead of Cleaner:
cleanMethod = lookup.findVirtual(cleanerClass, "run", methodType(void.class));
} else {
// can be either the old internal "sun.misc.Cleaner" or
// the new Java 9 "java.lang.ref.Cleaner$Cleanable":
cleanMethod = lookup.findVirtual(cleanerClass, "clean", methodType(void.class));
}
final MethodHandle nonNullTest = explicitCastArguments(lookup.findStatic(Objects.class, "nonNull", methodType(boolean.class, Object.class)),
methodType(boolean.class, cleanerClass));
final MethodHandle noop = dropArguments(explicitCastArguments(constant(Void.class, null), methodType(void.class)), 0, cleanerClass);
final MethodHandle unmapper = explicitCastArguments(filterReturnValue(directBufferCleanerMethod, guardWithTest(nonNullTest, cleanMethod, noop)),
methodType(void.class, ByteBuffer.class));
final MethodHandle nonNullTest = lookup.findStatic(Objects.class, "nonNull", methodType(boolean.class, Object.class))
.asType(methodType(boolean.class, cleanerClass));
final MethodHandle noop = dropArguments(constant(Void.class, null).asType(methodType(void.class)), 0, cleanerClass);
final MethodHandle unmapper = filterReturnValue(directBufferCleanerMethod, guardWithTest(nonNullTest, cleanMethod, noop))
.asType(methodType(void.class, ByteBuffer.class));
return (BufferCleaner) (ByteBufferIndexInput parent, ByteBuffer buffer) -> {
if (directBufferClass.isInstance(buffer)) {