388 lines
15 KiB
C++
388 lines
15 KiB
C++
/**
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* @file lleventcoro.h
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* @author Nat Goodspeed
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* @date 2009-04-29
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* @brief Utilities to interface between coroutines and events.
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*
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* $LicenseInfo:firstyear=2009&license=viewerlgpl$
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* Second Life Viewer Source Code
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* Copyright (C) 2010, Linden Research, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation;
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* version 2.1 of the License only.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
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* $/LicenseInfo$
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*/
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#if ! defined(LL_LLEVENTCORO_H)
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#define LL_LLEVENTCORO_H
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#include <boost/optional.hpp>
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#include <string>
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#include <utility> // std::pair
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#include "llevents.h"
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#include "llerror.h"
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#include "llexception.h"
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/**
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* Like LLListenerOrPumpName, this is a class intended for parameter lists:
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* accept a <tt>const LLEventPumpOrPumpName&</tt> and you can accept either an
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* <tt>LLEventPump&</tt> or its string name. For a single parameter that could
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* be either, it's not hard to overload the function -- but as soon as you
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* want to accept two such parameters, this is cheaper than four overloads.
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*/
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class LLEventPumpOrPumpName
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{
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public:
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/// Pass an actual LLEventPump&
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LLEventPumpOrPumpName(LLEventPump& pump):
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mPump(pump)
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{}
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/// Pass the string name of an LLEventPump
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LLEventPumpOrPumpName(const std::string& pumpname):
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mPump(LLEventPumps::instance().obtain(pumpname))
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{}
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/// Pass string constant name of an LLEventPump. This override must be
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/// explicit, since otherwise passing <tt>const char*</tt> to a function
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/// accepting <tt>const LLEventPumpOrPumpName&</tt> would require two
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/// different implicit conversions: <tt>const char*</tt> -> <tt>const
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/// std::string&</tt> -> <tt>const LLEventPumpOrPumpName&</tt>.
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LLEventPumpOrPumpName(const char* pumpname):
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mPump(LLEventPumps::instance().obtain(pumpname))
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{}
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/// Unspecified: "I choose not to identify an LLEventPump."
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LLEventPumpOrPumpName() {}
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operator LLEventPump& () const { return *mPump; }
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LLEventPump& getPump() const { return *mPump; }
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operator bool() const { return bool(mPump); }
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bool operator!() const { return ! mPump; }
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private:
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boost::optional<LLEventPump&> mPump;
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};
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namespace llcoro
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{
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/**
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* Yield control from a coroutine for one "mainloop" tick. If your coroutine
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* runs without suspending for nontrivial time, sprinkle in calls to this
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* function to avoid stalling the rest of the viewer processing.
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*/
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void suspend();
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/**
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* Yield control from a coroutine for at least the specified number of seconds
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*/
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void suspendUntilTimeout(float seconds);
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/**
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* Post specified LLSD event on the specified LLEventPump, then suspend for a
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* response on specified other LLEventPump. This is more than mere
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* convenience: the difference between this function and the sequence
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* @code
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* requestPump.post(myEvent);
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* LLSD reply = suspendUntilEventOn(replyPump);
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* @endcode
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* is that the sequence above fails if the reply is posted immediately on
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* @a replyPump, that is, before <tt>requestPump.post()</tt> returns. In the
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* sequence above, the running coroutine isn't even listening on @a replyPump
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* until <tt>requestPump.post()</tt> returns and @c suspendUntilEventOn() is
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* entered. Therefore, the coroutine completely misses an immediate reply
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* event, making it suspend indefinitely.
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*
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* By contrast, postAndSuspend() listens on the @a replyPump @em before posting
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* the specified LLSD event on the specified @a requestPump.
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*
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* @param event LLSD data to be posted on @a requestPump
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* @param requestPump an LLEventPump on which to post @a event. Pass either
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* the LLEventPump& or its string name. However, if you pass a
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* default-constructed @c LLEventPumpOrPumpName, we skip the post() call.
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* @param replyPump an LLEventPump on which postAndSuspend() will listen for a
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* reply. Pass either the LLEventPump& or its string name. The calling
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* coroutine will suspend until that reply arrives. (If you're concerned about a
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* reply that might not arrive, please see also LLEventTimeout.)
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* @param replyPumpNamePath specifies the location within @a event in which to
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* store <tt>replyPump.getName()</tt>. This is a strictly optional convenience
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* feature; obviously you can store the name in @a event "by hand" if desired.
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* @a replyPumpNamePath can be specified in any of four forms:
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* * @c isUndefined() (default-constructed LLSD object): do nothing. This is
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* the default behavior if you omit @a replyPumpNamePath.
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* * @c isInteger(): @a event is an array. Store <tt>replyPump.getName()</tt>
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* in <tt>event[replyPumpNamePath.asInteger()]</tt>.
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* * @c isString(): @a event is a map. Store <tt>replyPump.getName()</tt> in
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* <tt>event[replyPumpNamePath.asString()]</tt>.
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* * @c isArray(): @a event has several levels of structure, e.g. map of
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* maps, array of arrays, array of maps, map of arrays, ... Store
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* <tt>replyPump.getName()</tt> in
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* <tt>event[replyPumpNamePath[0]][replyPumpNamePath[1]]...</tt> In other
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* words, examine each array entry in @a replyPumpNamePath in turn. If it's an
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* <tt>LLSD::String</tt>, the current level of @a event is a map; step down to
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* that map entry. If it's an <tt>LLSD::Integer</tt>, the current level of @a
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* event is an array; step down to that array entry. The last array entry in
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* @a replyPumpNamePath specifies the entry in the lowest-level structure in
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* @a event into which to store <tt>replyPump.getName()</tt>.
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*/
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LLSD postAndSuspend(const LLSD& event, const LLEventPumpOrPumpName& requestPump,
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const LLEventPumpOrPumpName& replyPump, const LLSD& replyPumpNamePath=LLSD());
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/// Wait for the next event on the specified LLEventPump. Pass either the
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/// LLEventPump& or its string name.
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inline
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LLSD suspendUntilEventOn(const LLEventPumpOrPumpName& pump)
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{
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// This is now a convenience wrapper for postAndSuspend().
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return postAndSuspend(LLSD(), LLEventPumpOrPumpName(), pump);
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}
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/// Suspend the coroutine until an event is fired on the identified pump
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/// or the timeout duration has elapsed. If the timeout duration
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/// elapses the specified LLSD is returned.
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LLSD suspendUntilEventOnWithTimeout(const LLEventPumpOrPumpName& suspendPumpOrName, F32 timeoutin, const LLSD &timeoutResult);
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} // namespace llcoro
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/// return type for two-pump variant of suspendUntilEventOn()
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typedef std::pair<LLSD, int> LLEventWithID;
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namespace llcoro
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{
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/**
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* This function waits for a reply on either of two specified LLEventPumps.
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* Otherwise, it closely resembles postAndSuspend(); please see the documentation
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* for that function for detailed parameter info.
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*
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* While we could have implemented the single-pump variant in terms of this
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* one, there's enough added complexity here to make it worthwhile to give the
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* single-pump variant its own straightforward implementation. Conversely,
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* though we could use preprocessor logic to generate n-pump overloads up to
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* BOOST_COROUTINE_WAIT_MAX, we don't foresee a use case. This two-pump
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* overload exists because certain event APIs are defined in terms of a reply
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* LLEventPump and an error LLEventPump.
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*
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* The LLEventWithID return value provides not only the received event, but
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* the index of the pump on which it arrived (0 or 1).
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*
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* @note
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* I'd have preferred to overload the name postAndSuspend() for both signatures.
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* But consider the following ambiguous call:
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* @code
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* postAndSuspend(LLSD(), requestPump, replyPump, "someString");
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* @endcode
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* "someString" could be converted to either LLSD (@a replyPumpNamePath for
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* the single-pump function) or LLEventOrPumpName (@a replyPump1 for two-pump
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* function).
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*
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* It seems less burdensome to write postAndSuspend2() than to write either
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* LLSD("someString") or LLEventOrPumpName("someString").
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*/
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LLEventWithID postAndSuspend2(const LLSD& event,
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const LLEventPumpOrPumpName& requestPump,
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const LLEventPumpOrPumpName& replyPump0,
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const LLEventPumpOrPumpName& replyPump1,
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const LLSD& replyPump0NamePath=LLSD(),
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const LLSD& replyPump1NamePath=LLSD());
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/**
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* Wait for the next event on either of two specified LLEventPumps.
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*/
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inline
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LLEventWithID
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suspendUntilEventOn(const LLEventPumpOrPumpName& pump0, const LLEventPumpOrPumpName& pump1)
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{
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// This is now a convenience wrapper for postAndSuspend2().
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return postAndSuspend2(LLSD(), LLEventPumpOrPumpName(), pump0, pump1);
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}
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/**
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* Helper for the two-pump variant of suspendUntilEventOn(), e.g.:
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*
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* @code
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* LLSD reply = errorException(suspendUntilEventOn(replyPump, errorPump),
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* "error response from login.cgi");
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* @endcode
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*
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* Examines an LLEventWithID, assuming that the second pump (pump 1) is
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* listening for an error indication. If the incoming data arrived on pump 1,
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* throw an LLErrorEvent exception. If the incoming data arrived on pump 0,
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* just return it. Since a normal return can only be from pump 0, we no longer
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* need the LLEventWithID's discriminator int; we can just return the LLSD.
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*
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* @note I'm not worried about introducing the (fairly generic) name
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* errorException() into global namespace, because how many other overloads of
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* the same name are going to accept an LLEventWithID parameter?
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*/
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LLSD errorException(const LLEventWithID& result, const std::string& desc);
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} // namespace llcoro
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/**
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* Exception thrown by errorException(). We don't call this LLEventError
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* because it's not an error in event processing: rather, this exception
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* announces an event that bears error information (for some other API).
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*/
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class LL_COMMON_API LLErrorEvent: public LLException
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{
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public:
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LLErrorEvent(const std::string& what, const LLSD& data):
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LLException(what),
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mData(data)
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{}
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virtual ~LLErrorEvent() throw() {}
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LLSD getData() const { return mData; }
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private:
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LLSD mData;
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};
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namespace llcoro
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{
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/**
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* Like errorException(), save that this trips a fatal error using LL_ERRS
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* rather than throwing an exception.
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*/
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LL_COMMON_API LLSD errorLog(const LLEventWithID& result, const std::string& desc);
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} // namespace llcoro
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/**
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* Certain event APIs require the name of an LLEventPump on which they should
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* post results. While it works to invent a distinct name and let
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* LLEventPumps::obtain() instantiate the LLEventPump as a "named singleton,"
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* in a certain sense it's more robust to instantiate a local LLEventPump and
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* provide its name instead. This class packages the following idiom:
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*
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* 1. Instantiate a local LLCoroEventPump, with an optional name prefix.
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* 2. Provide its actual name to the event API in question as the name of the
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* reply LLEventPump.
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* 3. Initiate the request to the event API.
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* 4. Call your LLEventTempStream's suspend() method to suspend for the reply.
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* 5. Let the LLCoroEventPump go out of scope.
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*/
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class LL_COMMON_API LLCoroEventPump
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{
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public:
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LLCoroEventPump(const std::string& name="coro"):
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mPump(name, true) // allow tweaking the pump instance name
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{}
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/// It's typical to request the LLEventPump name to direct an event API to
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/// send its response to this pump.
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std::string getName() const { return mPump.getName(); }
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/// Less typically, we'd request the pump itself for some reason.
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LLEventPump& getPump() { return mPump; }
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/**
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* Wait for an event on this LLEventPump.
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*/
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LLSD suspend()
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{
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return llcoro::suspendUntilEventOn(mPump);
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}
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LLSD postAndSuspend(const LLSD& event, const LLEventPumpOrPumpName& requestPump,
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const LLSD& replyPumpNamePath=LLSD())
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{
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return llcoro::postAndSuspend(event, requestPump, mPump, replyPumpNamePath);
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}
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private:
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LLEventStream mPump;
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};
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/**
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* Other event APIs require the names of two different LLEventPumps: one for
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* success response, the other for error response. Extend LLCoroEventPump
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* for the two-pump use case.
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*/
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class LL_COMMON_API LLCoroEventPumps
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{
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public:
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LLCoroEventPumps(const std::string& name="coro",
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const std::string& suff0="Reply",
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const std::string& suff1="Error"):
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mPump0(name + suff0, true), // allow tweaking the pump instance name
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mPump1(name + suff1, true)
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{}
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/// request pump 0's name
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std::string getName0() const { return mPump0.getName(); }
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/// request pump 1's name
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std::string getName1() const { return mPump1.getName(); }
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/// request both names
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std::pair<std::string, std::string> getNames() const
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{
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return std::pair<std::string, std::string>(mPump0.getName(), mPump1.getName());
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}
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/// request pump 0
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LLEventPump& getPump0() { return mPump0; }
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/// request pump 1
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LLEventPump& getPump1() { return mPump1; }
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/// suspendUntilEventOn(either of our two LLEventPumps)
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LLEventWithID suspend()
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{
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return llcoro::suspendUntilEventOn(mPump0, mPump1);
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}
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/// errorException(suspend())
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LLSD suspendWithException()
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{
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return llcoro::errorException(suspend(), std::string("Error event on ") + getName1());
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}
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/// errorLog(suspend())
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LLSD suspendWithLog()
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{
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return llcoro::errorLog(suspend(), std::string("Error event on ") + getName1());
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}
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LLEventWithID postAndSuspend(const LLSD& event,
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const LLEventPumpOrPumpName& requestPump,
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const LLSD& replyPump0NamePath=LLSD(),
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const LLSD& replyPump1NamePath=LLSD())
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{
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return llcoro::postAndSuspend2(event, requestPump, mPump0, mPump1,
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replyPump0NamePath, replyPump1NamePath);
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}
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LLSD postAndSuspendWithException(const LLSD& event,
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const LLEventPumpOrPumpName& requestPump,
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const LLSD& replyPump0NamePath=LLSD(),
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const LLSD& replyPump1NamePath=LLSD())
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{
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return llcoro::errorException(postAndSuspend(event, requestPump,
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replyPump0NamePath, replyPump1NamePath),
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std::string("Error event on ") + getName1());
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}
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LLSD postAndSuspendWithLog(const LLSD& event,
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const LLEventPumpOrPumpName& requestPump,
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const LLSD& replyPump0NamePath=LLSD(),
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const LLSD& replyPump1NamePath=LLSD())
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{
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return llcoro::errorLog(postAndSuspend(event, requestPump,
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replyPump0NamePath, replyPump1NamePath),
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std::string("Error event on ") + getName1());
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}
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private:
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LLEventStream mPump0, mPump1;
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};
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#endif /* ! defined(LL_LLEVENTCORO_H) */
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