include/nativehelper/JniInvocation.h

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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 JNI_INVOCATION_H_included
#define JNI_INVOCATION_H_included

#include <jni.h>
#include "module_api.h"

struct JniInvocationImpl;

MODULE_API struct JniInvocationImpl* JniInvocationCreate();
MODULE_API void JniInvocationDestroy(struct JniInvocationImpl* instance);
MODULE_API int JniInvocationInit(struct JniInvocationImpl* instance, const char* library);
MODULE_API const char* JniInvocationGetLibrary(const char* library, char* buffer);

#ifdef __cplusplus

// JniInvocation adds a layer of indirection for applications using
// the JNI invocation API to allow the JNI implementation to be
// selected dynamically. Apps can specify a specific implementation to
// be used by calling InitJniInvocation. If this is not done, the
// library will chosen based on the value of Android system property
// persist.sys.dalvik.vm.lib on the device, and otherwise fall back to
// a hard-coded default implementation.
class JniInvocation final {
 public:
  JniInvocation() {
    impl_ = JniInvocationCreate();
  }

  ~JniInvocation() {
    JniInvocationDestroy(impl_);
  }

  // Initialize JNI invocation API. library should specifiy a valid
  // shared library for opening via dlopen providing a JNI invocation
  // implementation, or null to allow defaulting via
  // persist.sys.dalvik.vm.lib.
  bool Init(const char* library) {
    return JniInvocationInit(impl_, library) != 0;
  }

  // Exposes which library is actually loaded from the given name. The
  // buffer of size PROPERTY_VALUE_MAX will be used to load the system
  // property for the default library, if necessary. If no buffer is
  // provided, the fallback value will be used.
  static const char* GetLibrary(const char* library, char* buffer) {
    return JniInvocationGetLibrary(library, buffer);
  }

 private:
  JniInvocation(const JniInvocation&) = delete;
  JniInvocation& operator=(const JniInvocation&) = delete;

  static const char* GetLibrary(const char* library, char* buffer, bool (*is_debuggable)(),
                                int (*get_library_system_property)(char* buffer));

  JniInvocationImpl* impl_;

  friend class JNIInvocation_Debuggable_Test;
  friend class JNIInvocation_NonDebuggable_Test;
};

#endif  // __cplusplus

#endif  // JNI_INVOCATION_H_included