Michael Davidsaver
ec0b21d27c
previously, ~SingleSourceSubscriptionCtx would ~MonitorControlOp before the base class ~SubscriptionCtx would db_cancel_event() leading to a use-after-free.
83 lines
2.2 KiB
C++
83 lines
2.2 KiB
C++
/*
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* Copyright - See the COPYRIGHT that is included with this distribution.
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* pvxs is distributed subject to a Software License Agreement found
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* in file LICENSE that is included with this distribution.
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*
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* Author George S. McIntyre <george@level-n.com>, 2023
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*
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*/
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#ifndef PVXS_SUBSCRIPTIONCTX_H
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#define PVXS_SUBSCRIPTIONCTX_H
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#include <memory>
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#include <stdexcept>
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#include <type_traits>
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#include <dbEvent.h>
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#include "channel.h"
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#include "dbeventcontextdeleter.h"
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namespace pvxs {
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namespace ioc {
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class Subscription {
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std::shared_ptr<std::remove_pointer<dbEventSubscription>::type> sub; // holds void* returned by db_add_event()
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public:
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/* Add a subscription event by calling db_add_event using the given subscriptionCtx
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* and selecting the correct elements based on the given type of event being added.
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* You need to specify the correct options that correspond to the event type.
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* Adds a deleter to clean up the subscription by calling db_cancel_event.
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*/
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void subscribe(dbEventCtx context,
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const Channel& pChan,
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EVENTFUNC *user_sub, void *user_arg, unsigned select)
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{
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auto chan(pChan); // bind by value
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sub.reset(db_add_event(context, chan,
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user_sub, user_arg, select),
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[chan](dbEventSubscription sub) mutable
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{
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db_cancel_event(sub);
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chan = Channel(); // dbChannel* must outlive subscription
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});
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if(!sub)
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throw std::runtime_error("Failed to create db subscription");
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}
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void cancel() {
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sub.reset();
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}
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void enable() {
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if(sub) {
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db_event_enable(sub.get());
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db_post_single_event(sub.get());
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}
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}
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void disable() {
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if(sub)
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db_event_disable(sub.get());
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}
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};
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/**
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* A subscription context
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*/
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class SubscriptionCtx {
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public:
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// For locking access to subscription context
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Subscription pValueEventSubscription;
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Subscription pPropertiesEventSubscription;
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bool hadValueEvent = false;
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bool hadPropertyEvent = false;
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void cancel() {
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pValueEventSubscription.cancel();
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pPropertiesEventSubscription.cancel();
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}
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};
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} // ioc
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} // pvxs
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#endif //PVXS_SUBSCRIPTIONCTX_H
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