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/access.inline.hpp"
  29 #include "oops/oop.hpp"
  30 #include "runtime/jniHandles.hpp"
  31 #include "utilities/debug.hpp"
  32 #include "utilities/globalDefinitions.hpp"
  33 
  34 inline bool JNIHandles::is_jweak(jobject handle) {
  35   STATIC_ASSERT(weak_tag_size == 1);
  36   STATIC_ASSERT(weak_tag_value == 1);
  37   return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0;
  38 }
  39 
  40 inline oop* JNIHandles::jobject_ptr(jobject handle) {
  41   assert(!is_jweak(handle), "precondition");
  42   return reinterpret_cast<oop*>(handle);
  43 }
  44 
  45 inline oop* JNIHandles::jweak_ptr(jobject handle) {
  46   assert(is_jweak(handle), "precondition");
  47   char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value;
  48   return reinterpret_cast<oop*>(ptr);
  49 }
  50 
  51 // external_guard is true if called from resolve_external_guard.
  52 template<bool external_guard>
  53 inline oop JNIHandles::resolve_impl(jobject handle) {
  54   assert(handle != NULL, "precondition");
  55   assert(!current_thread_in_native(), "must not be in native");
  56   oop result;
  57   if (is_jweak(handle)) {       // Unlikely
  58     result = resolve_jweak(handle);
  59   } else {
  60     result = RootAccess<IN_CONCURRENT_ROOT>::oop_load(jobject_ptr(handle));
  61     // Construction of jobjects canonicalize a null value into a null
  62     // jobject, so for non-jweak the pointee should never be null.
  63     assert(external_guard || result != NULL, "Invalid JNI handle");
  64   }
  65   return result;
  66 }
  67 
  68 inline oop JNIHandles::resolve(jobject handle) {
  69   oop result = NULL;
  70   if (handle != NULL) {
  71     result = resolve_impl<false /* external_guard */ >(handle);
  72   }
  73   return result;
  74 }
  75 
  76 inline oop JNIHandles::resolve_non_null(jobject handle) {
  77   assert(handle != NULL, "JNI handle should not be null");
  78   oop result = resolve_impl<false /* external_guard */ >(handle);
  79   assert(result != NULL, "NULL read from jni handle");
  80   return result;
  81 }
  82 
  83 inline void JNIHandles::destroy_local(jobject handle) {
  84   if (handle != NULL) {
  85     assert(!is_jweak(handle), "Invalid JNI local handle");
  86     RootAccess<>::oop_store(jobject_ptr(handle), (oop)NULL);
  87   }
  88 }
  89 
  90 #endif // SHARE_RUNTIME_JNIHANDLES_INLINE_HPP
  91