1 /*
   2  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_RUNTIME_JNIHANDLES_INLINE_HPP
  26 #define SHARE_RUNTIME_JNIHANDLES_INLINE_HPP
  27 
  28 #include "oops/oop.hpp"
  29 #include "runtime/jniHandles.hpp"
  30 #include "utilities/debug.hpp"
  31 #include "utilities/globalDefinitions.hpp"
  32 
  33 inline bool JNIHandles::is_jweak(jobject handle) {
  34   STATIC_ASSERT(weak_tag_size == 1);
  35   STATIC_ASSERT(weak_tag_value == 1);
  36   return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0;
  37 }
  38 
  39 inline oop& JNIHandles::jobject_ref(jobject handle) {
  40   assert(!is_jweak(handle), "precondition");
  41   return *reinterpret_cast<oop*>(handle);
  42 }
  43 
  44 inline oop& JNIHandles::jweak_ref(jobject handle) {
  45   assert(is_jweak(handle), "precondition");
  46   char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value;
  47   return *reinterpret_cast<oop*>(ptr);
  48 }
  49 
  50 // external_guard is true if called from resolve_external_guard.
  51 template<bool external_guard>
  52 inline oop JNIHandles::resolve_impl(jobject handle) {
  53   assert(handle != NULL, "precondition");
  54   assert(!current_thread_in_native(), "must not be in native");
  55   oop result;
  56   if (is_jweak(handle)) {       // Unlikely
  57     result = resolve_jweak(handle);
  58   } else {
  59     result = jobject_ref(handle);
  60     // Construction of jobjects canonicalize a null value into a null
  61     // jobject, so for non-jweak the pointee should never be null.
  62     assert(external_guard || result != NULL, "Invalid JNI handle");
  63   }
  64   return result;
  65 }
  66 
  67 inline oop JNIHandles::resolve(jobject handle) {
  68   oop result = NULL;
  69   if (handle != NULL) {
  70     result = resolve_impl<false /* external_guard */ >(handle);
  71   }
  72   return result;
  73 }
  74 
  75 inline oop JNIHandles::resolve_non_null(jobject handle) {
  76   assert(handle != NULL, "JNI handle should not be null");
  77   oop result = resolve_impl<false /* external_guard */ >(handle);
  78   assert(result != NULL, "NULL read from jni handle");
  79   return result;
  80 }
  81 
  82 inline void JNIHandles::destroy_local(jobject handle) {
  83   if (handle != NULL) {
  84     assert(!is_jweak(handle), "Invalid JNI local handle");
  85     jobject_ref(handle) = NULL;
  86   }
  87 }
  88 
  89 #endif // SHARE_RUNTIME_JNIHANDLES_INLINE_HPP
  90