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https://github.com/facebook/rocksdb.git
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38 lines
1.6 KiB
C
38 lines
1.6 KiB
C
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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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/*
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* This macro is used for 32 bit OS. In 32 bit OS, the result number is a
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negative number if we use reinterpret_cast<jlong>(pointer).
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* For example, jlong ptr = reinterpret_cast<jlong>(pointer), ptr is a negative
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number in 32 bit OS.
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* If we check ptr using ptr > 0, it fails. For example, the following code is
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not correct.
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* if (jblock_cache_handle > 0) {
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std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *pCache =
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reinterpret_cast<std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *>(
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jblock_cache_handle);
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options.block_cache = *pCache;
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}
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* But the result number is positive number if we do
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reinterpret_cast<size_t>(pointer) first and then cast it to jlong. size_t is 4
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bytes long in 32 bit OS and 8 bytes long in 64 bit OS.
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static_cast<jlong>(reinterpret_cast<size_t>(_pointer)) is also working in 64
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bit OS.
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*
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* We don't need an opposite cast because it works from jlong to c++ pointer in
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both 32 bit and 64 bit OS.
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* For example, the following code is working in both 32 bit and 64 bit OS.
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jblock_cache_handle is jlong.
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* std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *pCache =
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reinterpret_cast<std::shared_ptr<ROCKSDB_NAMESPACE::Cache> *>(
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jblock_cache_handle);
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*/
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#define GET_CPLUSPLUS_POINTER(_pointer) \
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static_cast<jlong>(reinterpret_cast<size_t>(_pointer))
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