/** * @file lleventcoro.h * @author Nat Goodspeed * @date 2009-04-29 * @brief Utilities to interface between coroutines and events. * * $LicenseInfo:firstyear=2009&license=viewergpl$ * Copyright (c) 2009, Linden Research, Inc. * $/LicenseInfo$ */ #if ! defined(LL_LLEVENTCORO_H) #define LL_LLEVENTCORO_H #include <boost/coroutine/coroutine.hpp> #include <boost/coroutine/future.hpp> #include <boost/optional.hpp> #include <string> #include <stdexcept> #include "llevents.h" #include "llerror.h" /** * Like LLListenerOrPumpName, this is a class intended for parameter lists: * accept a <tt>const LLEventPumpOrPumpName&</tt> and you can accept either an * <tt>LLEventPump&</tt> or its string name. For a single parameter that could * be either, it's not hard to overload the function -- but as soon as you * want to accept two such parameters, this is cheaper than four overloads. */ class LLEventPumpOrPumpName { public: /// Pass an actual LLEventPump& LLEventPumpOrPumpName(LLEventPump& pump): mPump(pump) {} /// Pass the string name of an LLEventPump LLEventPumpOrPumpName(const std::string& pumpname): mPump(LLEventPumps::instance().obtain(pumpname)) {} /// Pass string constant name of an LLEventPump. This override must be /// explicit, since otherwise passing <tt>const char*</tt> to a function /// accepting <tt>const LLEventPumpOrPumpName&</tt> would require two /// different implicit conversions: <tt>const char*</tt> -> <tt>const /// std::string&</tt> -> <tt>const LLEventPumpOrPumpName&</tt>. LLEventPumpOrPumpName(const char* pumpname): mPump(LLEventPumps::instance().obtain(pumpname)) {} /// Unspecified: "I choose not to identify an LLEventPump." LLEventPumpOrPumpName() {} operator LLEventPump& () const { return *mPump; } LLEventPump& getPump() const { return *mPump; } operator bool() const { return mPump; } bool operator!() const { return ! mPump; } private: boost::optional<LLEventPump&> mPump; }; /// This is an adapter for a signature like void LISTENER(const LLSD&), which /// isn't a valid LLEventPump listener: such listeners should return bool. template <typename LISTENER> class LLVoidListener { public: LLVoidListener(const LISTENER& listener): mListener(listener) {} bool operator()(const LLSD& event) { mListener(event); // don't swallow the event, let other listeners see it return false; } private: LISTENER mListener; }; /// LLVoidListener helper function to infer the type of the LISTENER template <typename LISTENER> LLVoidListener<LISTENER> voidlistener(const LISTENER& listener) { return LLVoidListener<LISTENER>(listener); } namespace LLEventDetail { /** * waitForEventOn() permits a coroutine to temporarily listen on an * LLEventPump any number of times. We don't really want to have to ask * the caller to label each such call with a distinct string; the whole * point of waitForEventOn() is to present a nice sequential interface to * the underlying LLEventPump-with-named-listeners machinery. So we'll use * LLEventPump::inventName() to generate a distinct name for each * temporary listener. On the other hand, because a given coroutine might * call waitForEventOn() any number of times, we don't really want to * consume an arbitrary number of generated inventName()s: that namespace, * though large, is nonetheless finite. So we memoize an invented name for * each distinct coroutine instance (each different 'self' object). We * can't know the type of 'self', because it depends on the coroutine * body's signature. So we cast its address to void*, looking for distinct * pointer values. Yes, that means that an early coroutine could cache a * value here, then be destroyed, only to be supplanted by a later * coroutine (of the same or different type), and we'll end up * "recognizing" the second one and reusing the listener name -- but * that's okay, since it won't collide with any listener name used by the * earlier coroutine since that earlier coroutine no longer exists. */ template <typename COROUTINE_SELF> std::string listenerNameForCoro(COROUTINE_SELF& self) { return listenerNameForCoroImpl(self.get_id()); } /// Implementation for listenerNameForCoro() LL_COMMON_API std::string listenerNameForCoroImpl(const void* self_id); /** * Implement behavior described for postAndWait()'s @a replyPumpNamePath * parameter: * * * If <tt>path.isUndefined()</tt>, do nothing. * * If <tt>path.isString()</tt>, @a dest is an LLSD map: store @a value * into <tt>dest[path.asString()]</tt>. * * If <tt>path.isInteger()</tt>, @a dest is an LLSD array: store @a * value into <tt>dest[path.asInteger()]</tt>. * * If <tt>path.isArray()</tt>, iteratively apply the rules above to step * down through the structure of @a dest. The last array entry in @a * path specifies the entry in the lowest-level structure in @a dest * into which to store @a value. * * @note * In the degenerate case in which @a path is an empty array, @a dest will * @em become @a value rather than @em containing it. */ LL_COMMON_API void storeToLLSDPath(LLSD& dest, const LLSD& path, const LLSD& value); } // namespace LLEventDetail /** * Post specified LLSD event on the specified LLEventPump, then wait for a * response on specified other LLEventPump. This is more than mere * convenience: the difference between this function and the sequence * @code * requestPump.post(myEvent); * LLSD reply = waitForEventOn(self, replyPump); * @endcode * is that the sequence above fails if the reply is posted immediately on * @a replyPump, that is, before <tt>requestPump.post()</tt> returns. In the * sequence above, the running coroutine isn't even listening on @a replyPump * until <tt>requestPump.post()</tt> returns and @c waitForEventOn() is * entered. Therefore, the coroutine completely misses an immediate reply * event, making it wait indefinitely. * * By contrast, postAndWait() listens on the @a replyPump @em before posting * the specified LLSD event on the specified @a requestPump. * * @param self The @c self object passed into a coroutine * @param event LLSD data to be posted on @a requestPump * @param requestPump an LLEventPump on which to post @a event. Pass either * the LLEventPump& or its string name. However, if you pass a * default-constructed @c LLEventPumpOrPumpName, we skip the post() call. * @param replyPump an LLEventPump on which postAndWait() will listen for a * reply. Pass either the LLEventPump& or its string name. The calling * coroutine will wait until that reply arrives. (If you're concerned about a * reply that might not arrive, please see also LLEventTimeout.) * @param replyPumpNamePath specifies the location within @a event in which to * store <tt>replyPump.getName()</tt>. This is a strictly optional convenience * feature; obviously you can store the name in @a event "by hand" if desired. * @a replyPumpNamePath can be specified in any of four forms: * * @c isUndefined() (default-constructed LLSD object): do nothing. This is * the default behavior if you omit @a replyPumpNamePath. * * @c isInteger(): @a event is an array. Store <tt>replyPump.getName()</tt> * in <tt>event[replyPumpNamePath.asInteger()]</tt>. * * @c isString(): @a event is a map. Store <tt>replyPump.getName()</tt> in * <tt>event[replyPumpNamePath.asString()]</tt>. * * @c isArray(): @a event has several levels of structure, e.g. map of * maps, array of arrays, array of maps, map of arrays, ... Store * <tt>replyPump.getName()</tt> in * <tt>event[replyPumpNamePath[0]][replyPumpNamePath[1]]...</tt> In other * words, examine each array entry in @a replyPumpNamePath in turn. If it's an * <tt>LLSD::String</tt>, the current level of @a event is a map; step down to * that map entry. If it's an <tt>LLSD::Integer</tt>, the current level of @a * event is an array; step down to that array entry. The last array entry in * @a replyPumpNamePath specifies the entry in the lowest-level structure in * @a event into which to store <tt>replyPump.getName()</tt>. */ template <typename SELF> LLSD postAndWait(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLEventPumpOrPumpName& replyPump, const LLSD& replyPumpNamePath=LLSD()) { // declare the future boost::coroutines::future<LLSD> future(self); // make a callback that will assign a value to the future, and listen on // the specified LLEventPump with that callback std::string listenerName(LLEventDetail::listenerNameForCoro(self)); LLTempBoundListener connection( replyPump.getPump().listen(listenerName, voidlistener(boost::coroutines::make_callback(future)))); // skip the "post" part if requestPump is default-constructed if (requestPump) { // If replyPumpNamePath is non-empty, store the replyPump name in the // request event. LLSD modevent(event); LLEventDetail::storeToLLSDPath(modevent, replyPumpNamePath, replyPump.getPump().getName()); LL_DEBUGS("lleventcoro") << "postAndWait(): coroutine " << listenerName << " posting to " << requestPump.getPump().getName() << LL_ENDL; // *NOTE:Mani - Removed because modevent could contain user's hashed passwd. // << ": " << modevent << LL_ENDL; requestPump.getPump().post(modevent); } LL_DEBUGS("lleventcoro") << "postAndWait(): coroutine " << listenerName << " about to wait on LLEventPump " << replyPump.getPump().getName() << LL_ENDL; // trying to dereference ("resolve") the future makes us wait for it LLSD value(*future); LL_DEBUGS("lleventcoro") << "postAndWait(): coroutine " << listenerName << " resuming with " << value << LL_ENDL; // returning should disconnect the connection return value; } /// Wait for the next event on the specified LLEventPump. Pass either the /// LLEventPump& or its string name. template <typename SELF> LLSD waitForEventOn(SELF& self, const LLEventPumpOrPumpName& pump) { // This is now a convenience wrapper for postAndWait(). return postAndWait(self, LLSD(), LLEventPumpOrPumpName(), pump); } /// return type for two-pump variant of waitForEventOn() typedef std::pair<LLSD, int> LLEventWithID; namespace LLEventDetail { /** * This helper is specifically for the two-pump version of waitForEventOn(). * We use a single future object, but we want to listen on two pumps with it. * Since we must still adapt from (the callable constructed by) * boost::coroutines::make_callback() (void return) to provide an event * listener (bool return), we've adapted LLVoidListener for the purpose. The * basic idea is that we construct a distinct instance of WaitForEventOnHelper * -- binding different instance data -- for each of the pumps. Then, when a * pump delivers an LLSD value to either WaitForEventOnHelper, it can combine * that LLSD with its discriminator to feed the future object. */ template <typename LISTENER> class WaitForEventOnHelper { public: WaitForEventOnHelper(const LISTENER& listener, int discriminator): mListener(listener), mDiscrim(discriminator) {} // this signature is required for an LLEventPump listener bool operator()(const LLSD& event) { // our future object is defined to accept LLEventWithID mListener(LLEventWithID(event, mDiscrim)); // don't swallow the event, let other listeners see it return false; } private: LISTENER mListener; const int mDiscrim; }; /// WaitForEventOnHelper type-inference helper template <typename LISTENER> WaitForEventOnHelper<LISTENER> wfeoh(const LISTENER& listener, int discriminator) { return WaitForEventOnHelper<LISTENER>(listener, discriminator); } } // namespace LLEventDetail /** * This function waits for a reply on either of two specified LLEventPumps. * Otherwise, it closely resembles postAndWait(); please see the documentation * for that function for detailed parameter info. * * While we could have implemented the single-pump variant in terms of this * one, there's enough added complexity here to make it worthwhile to give the * single-pump variant its own straightforward implementation. Conversely, * though we could use preprocessor logic to generate n-pump overloads up to * BOOST_COROUTINE_WAIT_MAX, we don't foresee a use case. This two-pump * overload exists because certain event APIs are defined in terms of a reply * LLEventPump and an error LLEventPump. * * The LLEventWithID return value provides not only the received event, but * the index of the pump on which it arrived (0 or 1). * * @note * I'd have preferred to overload the name postAndWait() for both signatures. * But consider the following ambiguous call: * @code * postAndWait(self, LLSD(), requestPump, replyPump, "someString"); * @endcode * "someString" could be converted to either LLSD (@a replyPumpNamePath for * the single-pump function) or LLEventOrPumpName (@a replyPump1 for two-pump * function). * * It seems less burdensome to write postAndWait2() than to write either * LLSD("someString") or LLEventOrPumpName("someString"). */ template <typename SELF> LLEventWithID postAndWait2(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLEventPumpOrPumpName& replyPump0, const LLEventPumpOrPumpName& replyPump1, const LLSD& replyPump0NamePath=LLSD(), const LLSD& replyPump1NamePath=LLSD()) { // declare the future boost::coroutines::future<LLEventWithID> future(self); // either callback will assign a value to this future; listen on // each specified LLEventPump with a callback std::string name(LLEventDetail::listenerNameForCoro(self)); LLTempBoundListener connection0( replyPump0.getPump().listen(name + "a", LLEventDetail::wfeoh(boost::coroutines::make_callback(future), 0))); LLTempBoundListener connection1( replyPump1.getPump().listen(name + "b", LLEventDetail::wfeoh(boost::coroutines::make_callback(future), 1))); // skip the "post" part if requestPump is default-constructed if (requestPump) { // If either replyPumpNamePath is non-empty, store the corresponding // replyPump name in the request event. LLSD modevent(event); LLEventDetail::storeToLLSDPath(modevent, replyPump0NamePath, replyPump0.getPump().getName()); LLEventDetail::storeToLLSDPath(modevent, replyPump1NamePath, replyPump1.getPump().getName()); LL_DEBUGS("lleventcoro") << "postAndWait2(): coroutine " << name << " posting to " << requestPump.getPump().getName() << ": " << modevent << LL_ENDL; requestPump.getPump().post(modevent); } LL_DEBUGS("lleventcoro") << "postAndWait2(): coroutine " << name << " about to wait on LLEventPumps " << replyPump0.getPump().getName() << ", " << replyPump1.getPump().getName() << LL_ENDL; // trying to dereference ("resolve") the future makes us wait for it LLEventWithID value(*future); LL_DEBUGS("lleventcoro") << "postAndWait(): coroutine " << name << " resuming with (" << value.first << ", " << value.second << ")" << LL_ENDL; // returning should disconnect both connections return value; } /** * Wait for the next event on either of two specified LLEventPumps. */ template <typename SELF> LLEventWithID waitForEventOn(SELF& self, const LLEventPumpOrPumpName& pump0, const LLEventPumpOrPumpName& pump1) { // This is now a convenience wrapper for postAndWait2(). return postAndWait2(self, LLSD(), LLEventPumpOrPumpName(), pump0, pump1); } /** * Helper for the two-pump variant of waitForEventOn(), e.g.: * * @code * LLSD reply = errorException(waitForEventOn(self, replyPump, errorPump), * "error response from login.cgi"); * @endcode * * Examines an LLEventWithID, assuming that the second pump (pump 1) is * listening for an error indication. If the incoming data arrived on pump 1, * throw an LLErrorEvent exception. If the incoming data arrived on pump 0, * just return it. Since a normal return can only be from pump 0, we no longer * need the LLEventWithID's discriminator int; we can just return the LLSD. * * @note I'm not worried about introducing the (fairly generic) name * errorException() into global namespace, because how many other overloads of * the same name are going to accept an LLEventWithID parameter? */ LLSD errorException(const LLEventWithID& result, const std::string& desc); /** * Exception thrown by errorException(). We don't call this LLEventError * because it's not an error in event processing: rather, this exception * announces an event that bears error information (for some other API). */ class LL_COMMON_API LLErrorEvent: public std::runtime_error { public: LLErrorEvent(const std::string& what, const LLSD& data): std::runtime_error(what), mData(data) {} virtual ~LLErrorEvent() throw() {} LLSD getData() const { return mData; } private: LLSD mData; }; /** * Like errorException(), save that this trips a fatal error using LL_ERRS * rather than throwing an exception. */ LL_COMMON_API LLSD errorLog(const LLEventWithID& result, const std::string& desc); /** * Certain event APIs require the name of an LLEventPump on which they should * post results. While it works to invent a distinct name and let * LLEventPumps::obtain() instantiate the LLEventPump as a "named singleton," * in a certain sense it's more robust to instantiate a local LLEventPump and * provide its name instead. This class packages the following idiom: * * 1. Instantiate a local LLCoroEventPump, with an optional name prefix. * 2. Provide its actual name to the event API in question as the name of the * reply LLEventPump. * 3. Initiate the request to the event API. * 4. Call your LLEventTempStream's wait() method to wait for the reply. * 5. Let the LLCoroEventPump go out of scope. */ class LL_COMMON_API LLCoroEventPump { public: LLCoroEventPump(const std::string& name="coro"): mPump(name, true) // allow tweaking the pump instance name {} /// It's typical to request the LLEventPump name to direct an event API to /// send its response to this pump. std::string getName() const { return mPump.getName(); } /// Less typically, we'd request the pump itself for some reason. LLEventPump& getPump() { return mPump; } /** * Wait for an event on this LLEventPump. * * @note * The other major usage pattern we considered was to bind @c self at * LLCoroEventPump construction time, which would avoid passing the * parameter to each wait() call. But if we were going to bind @c self as * a class member, we'd need to specify a class template parameter * indicating its type. The big advantage of passing it to the wait() call * is that the type can be implicit. */ template <typename SELF> LLSD wait(SELF& self) { return waitForEventOn(self, mPump); } template <typename SELF> LLSD postAndWait(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLSD& replyPumpNamePath=LLSD()) { return ::postAndWait(self, event, requestPump, mPump, replyPumpNamePath); } private: LLEventStream mPump; }; /** * Other event APIs require the names of two different LLEventPumps: one for * success response, the other for error response. Extend LLCoroEventPump * for the two-pump use case. */ class LL_COMMON_API LLCoroEventPumps { public: LLCoroEventPumps(const std::string& name="coro", const std::string& suff0="Reply", const std::string& suff1="Error"): mPump0(name + suff0, true), // allow tweaking the pump instance name mPump1(name + suff1, true) {} /// request pump 0's name std::string getName0() const { return mPump0.getName(); } /// request pump 1's name std::string getName1() const { return mPump1.getName(); } /// request both names std::pair<std::string, std::string> getNames() const { return std::pair<std::string, std::string>(mPump0.getName(), mPump1.getName()); } /// request pump 0 LLEventPump& getPump0() { return mPump0; } /// request pump 1 LLEventPump& getPump1() { return mPump1; } /// waitForEventOn(self, either of our two LLEventPumps) template <typename SELF> LLEventWithID wait(SELF& self) { return waitForEventOn(self, mPump0, mPump1); } /// errorException(wait(self)) template <typename SELF> LLSD waitWithException(SELF& self) { return errorException(wait(self), std::string("Error event on ") + getName1()); } /// errorLog(wait(self)) template <typename SELF> LLSD waitWithLog(SELF& self) { return errorLog(wait(self), std::string("Error event on ") + getName1()); } template <typename SELF> LLEventWithID postAndWait(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLSD& replyPump0NamePath=LLSD(), const LLSD& replyPump1NamePath=LLSD()) { return postAndWait2(self, event, requestPump, mPump0, mPump1, replyPump0NamePath, replyPump1NamePath); } template <typename SELF> LLSD postAndWaitWithException(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLSD& replyPump0NamePath=LLSD(), const LLSD& replyPump1NamePath=LLSD()) { return errorException(postAndWait(self, event, requestPump, replyPump0NamePath, replyPump1NamePath), std::string("Error event on ") + getName1()); } template <typename SELF> LLSD postAndWaitWithLog(SELF& self, const LLSD& event, const LLEventPumpOrPumpName& requestPump, const LLSD& replyPump0NamePath=LLSD(), const LLSD& replyPump1NamePath=LLSD()) { return errorLog(postAndWait(self, event, requestPump, replyPump0NamePath, replyPump1NamePath), std::string("Error event on ") + getName1()); } private: LLEventStream mPump0, mPump1; }; #endif /* ! defined(LL_LLEVENTCORO_H) */