jvmHeap.h

/*
 * Copyright 2023 Datadog, Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

 #ifndef _JVMHEAP_H
 #define _JVMHEAP_H

#include <cstddef>

 /**
  * This class only defines a layout compatible with the JDKs VirtualSpaceSummary class and particularly its subclasses
  */
 class VirtualSpaceSummary {
   private:
     void* _start;
     void* _committed_end;
     void* _reserved_end;
   public:
     long maxSize() {
         return (long)_reserved_end - (long)_start;
     }
 };

 /**
  * This class only defines a layout compatible with the JDKs GCHeapSummary class and particularly its subclasses
  */
 class GCHeapSummary {
   private:
     void* vptr; // only 1-st level subclasses are used so we need to define the 'synthetic' vptr field here
     VirtualSpaceSummary _heap;
     size_t _used;
   public:
     long used() {
         return (long)_used;
     }

     long maxSize() {
         return _heap.maxSize();
     }
 };

 /**
  * This class only defines a layout compatible with the JDKs CompatibleHeap class and particularly its subclasses
  */
 class CollectedHeap {
   private:
     void* vptr; // only 1-st level subclasses are used so we need to define the 'synthetic' vptr field here
     void* _gc_heap_log; // ignored
   public:
     // Historic gc information
     size_t _capacity_at_last_gc;
     size_t _used_at_last_gc;
 };

 #endif // _JVMHEAP_H