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106 lines
2.2 KiB
C++
106 lines
2.2 KiB
C++
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#pragma once
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#include <list>
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#include <mutex>
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#include <condition_variable>
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#include <Common/Exception.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int LOGICAL_ERROR;
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}
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struct RWLockFIFO;
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using RWLockFIFOPtr = std::shared_ptr<RWLockFIFO>;
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/// Implements shared lock with FIFO service
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class RWLockFIFO : public std::enable_shared_from_this<RWLockFIFO>
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{
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public:
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static RWLockFIFOPtr create()
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{
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return RWLockFIFOPtr(new RWLockFIFO);
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}
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enum Type
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{
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Read,
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Write
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};
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/// Client is that who wants to acquire the lock.
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struct Client
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{
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explicit Client(const std::string & info = "Anonymous client") : info{info} {}
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std::string info;
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};
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class LockHandlerImpl;
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using LockHandler = std::unique_ptr<LockHandlerImpl>;
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/// Waits in the queue and returns appropriate lock
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LockHandler getLock(Type type, Client client);
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LockHandler getLock(Type type, const std::string & who)
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{
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return getLock(type, Client(who));
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}
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private:
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RWLockFIFO() = default;
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struct Group;
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using GroupsContainer = std::list<Group>;
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using ClientsContainer = std::list<Client>;
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/// Group of clients that should be executed concurrently
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/// i.e. a group could contain several readers, but only one writer
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struct Group
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{
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const Type type;
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ClientsContainer clients;
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std::condition_variable cv; /// all clients of the group wait group condvar
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bool awakened{false}; /// just only to handle spurious wake ups
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explicit Group(Type type) : type{type} {}
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};
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public:
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class LockHandlerImpl
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{
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RWLockFIFOPtr parent;
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GroupsContainer::iterator it_group;
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ClientsContainer::iterator it_client;
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public:
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LockHandlerImpl(RWLockFIFOPtr && parent, GroupsContainer::iterator it_group, ClientsContainer::iterator it_client)
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: parent{std::move(parent)}, it_group{it_group}, it_client{it_client} {}
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LockHandlerImpl(const LockHandlerImpl & other) = delete;
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void unlock();
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~LockHandlerImpl();
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friend class RWLockFIFO;
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};
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private:
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std::mutex mutex;
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GroupsContainer queue;
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};
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}
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