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java/rocksjni/cplusplus_to_java_convert.h
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Fix pointer to jlong conversion in 32 bit OS (#9396)
01 мар 2022, 20:02
01 мар 2022, 20:02
06c8afe
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// 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))