95 lines
3.2 KiB
C++
95 lines
3.2 KiB
C++
// 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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//
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// This file implements the callback "bridge" between Java and C++ for
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// rocksdb::Comparator and rocksdb::DirectComparator.
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#ifndef JAVA_ROCKSJNI_COMPARATORJNICALLBACK_H_
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#define JAVA_ROCKSJNI_COMPARATORJNICALLBACK_H_
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#include <jni.h>
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#include <string>
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#include "rocksdb/comparator.h"
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#include "rocksdb/slice.h"
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#include "port/port.h"
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namespace rocksdb {
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struct ComparatorJniCallbackOptions {
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// Use adaptive mutex, which spins in the user space before resorting
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// to kernel. This could reduce context switch when the mutex is not
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// heavily contended. However, if the mutex is hot, we could end up
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// wasting spin time.
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// Default: false
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bool use_adaptive_mutex;
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ComparatorJniCallbackOptions() : use_adaptive_mutex(false) {
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}
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};
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/**
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* This class acts as a bridge between C++
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* and Java. The methods in this class will be
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* called back from the RocksDB storage engine (C++)
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* we then callback to the appropriate Java method
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* this enables Comparators to be implemented in Java.
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*
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* The design of this Comparator caches the Java Slice
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* objects that are used in the compare and findShortestSeparator
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* method callbacks. Instead of creating new objects for each callback
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* of those functions, by reuse via setHandle we are a lot
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* faster; Unfortunately this means that we have to
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* introduce independent locking in regions of each of those methods
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* via the mutexs mtx_compare and mtx_findShortestSeparator respectively
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*/
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class BaseComparatorJniCallback : public Comparator {
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public:
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BaseComparatorJniCallback(
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JNIEnv* env, jobject jComparator,
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const ComparatorJniCallbackOptions* copt);
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virtual ~BaseComparatorJniCallback();
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virtual const char* Name() const;
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virtual int Compare(const Slice& a, const Slice& b) const;
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virtual void FindShortestSeparator(
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std::string* start, const Slice& limit) const;
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virtual void FindShortSuccessor(std::string* key) const;
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private:
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// used for synchronisation in compare method
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port::Mutex* mtx_compare;
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// used for synchronisation in findShortestSeparator method
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port::Mutex* mtx_findShortestSeparator;
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jobject m_jComparator;
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std::string m_name;
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jmethodID m_jCompareMethodId;
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jmethodID m_jFindShortestSeparatorMethodId;
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jmethodID m_jFindShortSuccessorMethodId;
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protected:
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JavaVM* m_jvm;
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jobject m_jSliceA;
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jobject m_jSliceB;
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jobject m_jSliceLimit;
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};
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class ComparatorJniCallback : public BaseComparatorJniCallback {
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public:
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ComparatorJniCallback(
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JNIEnv* env, jobject jComparator,
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const ComparatorJniCallbackOptions* copt);
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~ComparatorJniCallback();
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};
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class DirectComparatorJniCallback : public BaseComparatorJniCallback {
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public:
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DirectComparatorJniCallback(
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JNIEnv* env, jobject jComparator,
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const ComparatorJniCallbackOptions* copt);
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~DirectComparatorJniCallback();
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};
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} // namespace rocksdb
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#endif // JAVA_ROCKSJNI_COMPARATORJNICALLBACK_H_
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