src/share/vm/runtime/jniHandles.hpp

rev 12906 : [mq]: gc_interface

@@ -38,18 +38,80 @@
  private:
   static JNIHandleBlock* _global_handles;             // First global handle block
   static JNIHandleBlock* _weak_global_handles;        // First weak global handle block
   static oop _deleted_handle;                         // Sentinel marking deleted handles
 
+  inline static oop* oop_addr(jobject handle);
   inline static bool is_jweak(jobject handle);
-  inline static oop& jobject_ref(jobject handle); // NOT jweak!
-  inline static oop& jweak_ref(jobject handle);
 
   template<bool external_guard> inline static oop guard_value(oop value);
   template<bool external_guard> inline static oop resolve_impl(jobject handle);
   template<bool external_guard> static oop resolve_jweak(jweak handle);
 
+  static oop resolve_handle(jobject handle);
+
+  enum ResolveType {
+    DEFAULT,
+    EXTERNAL_GUARD,
+    NOT_NULL
+  };
+
+  template <ResolveType type>
+  class JNIHandleResolver: public StackObj {
+    oop _value;
+
+    bool is_not_null() const {
+      return type == NOT_NULL;
+    }
+
+    bool is_external_guard() const {
+      return type == EXTERNAL_GUARD;
+    }
+
+    bool is_default() const {
+      return type == DEFAULT;
+    }
+
+    bool is_dead(oop value) const {
+      return value == NULL || value == badJNIHandle || value == deleted_handle();
+    }
+
+    void assert_not_dead(oop value) const {
+      if (!is_external_guard()) {
+        assert(value != badJNIHandle, "Pointing to zapped jni handle area");
+        assert(value == NULL || value != deleted_handle(), "Used a deleted global handle");
+      }
+    }
+
+  public:
+    JNIHandleResolver(jobject handle) {
+      oop value;
+      assert(!is_not_null() || handle != NULL, "JNI handle should not be null");
+      if (!is_not_null() && handle == NULL) {
+        value = NULL;
+      } else {
+        value = *oop_addr(handle);
+        assert_not_dead(value);
+        if (is_external_guard() && is_dead(value)) {
+          value = NULL;
+        } else {
+          value = resolve_handle(handle);
+        }
+      }
+      _value = value;
+    }
+
+    oop value() const {
+      return _value;
+    }
+
+    ~JNIHandleResolver() {
+      assert_not_dead(_value);
+      assert(!is_not_null() || _value != NULL, "NULL read from jni handle");
+    }
+  };
+
  public:
   // Low tag bit in jobject used to distinguish a jweak.  jweak is
   // type equivalent to jobject, but there are places where we need to
   // be able to distinguish jweak values from other jobjects, and
   // is_weak_global_handle is unsuitable for performance reasons.  To

@@ -201,82 +263,32 @@
   STATIC_ASSERT(weak_tag_size == 1);
   STATIC_ASSERT(weak_tag_value == 1);
   return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0;
 }
 
-inline oop& JNIHandles::jobject_ref(jobject handle) {
-  assert(!is_jweak(handle), "precondition");
-  return *reinterpret_cast<oop*>(handle);
-}
-
-inline oop& JNIHandles::jweak_ref(jobject handle) {
-  assert(is_jweak(handle), "precondition");
-  char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value;
-  return *reinterpret_cast<oop*>(ptr);
-}
-
-// external_guard is true if called from resolve_external_guard.
-// Treat deleted (and possibly zapped) as NULL for external_guard,
-// else as (asserted) error.
-template<bool external_guard>
-inline oop JNIHandles::guard_value(oop value) {
-  if (!external_guard) {
-    assert(value != badJNIHandle, "Pointing to zapped jni handle area");
-    assert(value != deleted_handle(), "Used a deleted global handle");
-  } else if ((value == badJNIHandle) || (value == deleted_handle())) {
-    value = NULL;
-  }
-  return value;
-}
-
-// external_guard is true if called from resolve_external_guard.
-template<bool external_guard>
-inline oop JNIHandles::resolve_impl(jobject handle) {
-  assert(handle != NULL, "precondition");
-  oop result;
-  if (is_jweak(handle)) {       // Unlikely
-    result = resolve_jweak<external_guard>(handle);
-  } else {
-    result = jobject_ref(handle);
-    // Construction of jobjects canonicalize a null value into a null
-    // jobject, so for non-jweak the pointee should never be null.
-    assert(external_guard || result != NULL,
-           "Invalid value read from jni handle");
-    result = guard_value<external_guard>(result);
-  }
-  return result;
+inline oop* JNIHandles::oop_addr(jobject handle) {
+  return (oop*)(reinterpret_cast<uintptr_t>(handle) & ~(weak_tag_mask));
 }
 
 inline oop JNIHandles::resolve(jobject handle) {
-  oop result = NULL;
-  if (handle != NULL) {
-    result = resolve_impl<false /* external_guard */ >(handle);
-  }
-  return result;
+  return JNIHandleResolver<DEFAULT>(handle).value();
 }
 
 // Resolve some erroneous cases to NULL, rather than treating them as
 // possibly unchecked errors.  In particular, deleted handles are
 // treated as NULL (though a deleted and later reallocated handle
 // isn't detected).
 inline oop JNIHandles::resolve_external_guard(jobject handle) {
-  oop result = NULL;
-  if (handle != NULL) {
-    result = resolve_impl<true /* external_guard */ >(handle);
-  }
-  return result;
+  return JNIHandleResolver<EXTERNAL_GUARD>(handle).value();
 }
 
 inline oop JNIHandles::resolve_non_null(jobject handle) {
-  assert(handle != NULL, "JNI handle should not be null");
-  oop result = resolve_impl<false /* external_guard */ >(handle);
-  assert(result != NULL, "NULL read from jni handle");
-  return result;
+  return JNIHandleResolver<NOT_NULL>(handle).value();
 }
 
 inline void JNIHandles::destroy_local(jobject handle) {
   if (handle != NULL) {
-    jobject_ref(handle) = deleted_handle();
+    *oop_addr(handle) = deleted_handle();
   }
 }
 
 #endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP