1 files changed, 37 insertions, 0 deletions
diff --git a/src/rocksdb/java/rocksjni/cplusplus_to_java_convert.h b/src/rocksdb/java/rocksjni/cplusplus_to_java_convert.h
new file mode 100644
index 000000000..0eea6fa2c
--- /dev/null
+++ b/src/rocksdb/java/rocksjni/cplusplus_to_java_convert.h
@@ -0,0 +1,37 @@
+// 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).
+
+#pragma once
+
+/*
+ * This macro is used for 32 bit OS. In 32 bit OS, the result number is a
+ negative number if we use reinterpret_cast<jlong>(pointer).
+ * For example, jlong ptr = reinterpret_cast<jlong>(pointer), ptr is a negative
+ number in 32 bit OS.
+ * If we check ptr using ptr > 0, it fails. For example, the following code is
+ not correct.
+ * if (jblock_cache_handle > 0) {
+      std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *pCache =
+          reinterpret_cast<std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *>(
+              jblock_cache_handle);
+      options.block_cache = *pCache;
+    }
+ * But the result number is positive number if we do
+ reinterpret_cast<size_t>(pointer) first and then cast it to jlong. size_t is 4
+ bytes long in 32 bit OS and 8 bytes long in 64 bit OS.
+ static_cast<jlong>(reinterpret_cast<size_t>(_pointer)) is also working in 64
+ bit OS.
+ *
+ * We don't need an opposite cast because it works from jlong to c++ pointer in
+ both 32 bit and 64 bit OS.
+ * For example, the following code is working in both 32 bit and 64 bit OS.
+ jblock_cache_handle is jlong.
+ *   std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *pCache =
+          reinterpret_cast<std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *>(
+              jblock_cache_handle);
+*/
+
+#define GET_CPLUSPLUS_POINTER(_pointer) \
+  static_cast<jlong>(reinterpret_cast<size_t>(_pointer))