connectivity/source/inc/java/LocalRef.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
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  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #pragma once
  21
  22 #if defined __clang__
  23 #pragma clang diagnostic push
  24 #pragma clang diagnostic ignored "-Wunknown-attributes"
  25 #endif
  26 #include <jni.h>
  27 #if defined __clang__
  28 #pragma clang diagnostic pop
  29 #endif
  30
  31 namespace connectivity::jdbc
  32 {
  33
  34     /** helper class to hold a local ref to a JNI object
  35
  36         Note that this class never actually calls NewLocalRef. It is assumed that all objects
  37         passed are already acquired with a local ref (as it usually is the case if you obtain
  38         the object from a JNI method).
  39     */
  40     template< typename T >
  41     class LocalRef final
  42     {
  43     public:
  44         explicit LocalRef( JNIEnv& environment )
  45             :m_environment( environment )
  46             ,m_object( nullptr )
  47         {
  48         }
  49
  50         LocalRef( JNIEnv& environment, T object )
  51             :m_environment( environment )
  52             ,m_object( object )
  53         {
  54         }
  55
  56         ~LocalRef()
  57         {
  58             reset();
  59         }
  60
  61         T release()
  62         {
  63             T t = m_object;
  64             m_object = nullptr;
  65             return t;
  66         }
  67
  68         void set( T object ) { reset(); m_object = object; }
  69
  70         void reset()
  71         {
  72             if ( m_object != nullptr )
  73             {
  74                 m_environment.DeleteLocalRef( m_object );
  75                 m_object = nullptr;
  76             }
  77         }
  78
  79         JNIEnv& env() const { return m_environment; }
  80         T       get() const { return m_object; }
  81         bool    is()  const { return m_object != nullptr; }
  82
  83     private:
  84         LocalRef(LocalRef const &) = delete;
  85         LocalRef& operator =(LocalRef const &) = delete;
  86
  87         JNIEnv& m_environment;
  88         T       m_object;
  89     };
  90
  91
  92 } // namespace connectivity::jdbc
  93
  94
  95 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */