1 files changed, 54 insertions, 0 deletions
diff --git a/src/rocksdb/java/rocksjni/jnicallback.cc b/src/rocksdb/java/rocksjni/jnicallback.cc
new file mode 100644
index 000000000..f2742cd88
--- /dev/null
+++ b/src/rocksdb/java/rocksjni/jnicallback.cc
@@ -0,0 +1,54 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// This file implements the callback "bridge" between Java and C++ for
+// JNI Callbacks from C++ to sub-classes or org.rocksdb.RocksCallbackObject
+
+#include "rocksjni/jnicallback.h"
+
+#include <assert.h>
+
+#include "rocksjni/portal.h"
+
+namespace ROCKSDB_NAMESPACE {
+JniCallback::JniCallback(JNIEnv* env, jobject jcallback_obj) {
+  // Note: jcallback_obj may be accessed by multiple threads,
+  // so we ref the jvm not the env
+  const jint rs = env->GetJavaVM(&m_jvm);
+  if (rs != JNI_OK) {
+    // exception thrown
+    return;
+  }
+
+  // Note: we may want to access the Java callback object instance
+  // across multiple method calls, so we create a global ref
+  assert(jcallback_obj != nullptr);
+  m_jcallback_obj = env->NewGlobalRef(jcallback_obj);
+  if (jcallback_obj == nullptr) {
+    // exception thrown: OutOfMemoryError
+    return;
+  }
+}
+
+JNIEnv* JniCallback::getJniEnv(jboolean* attached) const {
+  return JniUtil::getJniEnv(m_jvm, attached);
+}
+
+void JniCallback::releaseJniEnv(jboolean& attached) const {
+  JniUtil::releaseJniEnv(m_jvm, attached);
+}
+
+JniCallback::~JniCallback() {
+  jboolean attached_thread = JNI_FALSE;
+  JNIEnv* env = getJniEnv(&attached_thread);
+  assert(env != nullptr);
+
+  if (m_jcallback_obj != nullptr) {
+    env->DeleteGlobalRef(m_jcallback_obj);
+  }
+
+  releaseJniEnv(attached_thread);
+}
+}  // namespace ROCKSDB_NAMESPACE