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/**
* @file lleventcoro.h
* @author Nat Goodspeed
* @date 2009-04-29
* @brief Utilities to interface between coroutines and events.
*
* $LicenseInfo:firstyear=2009&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#if ! defined(LL_LLEVENTCORO_H)
#define LL_LLEVENTCORO_H
#include <string>
#include "llevents.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 bool(mPump); }
bool operator!() const { return ! mPump; }
private:
boost::optional<LLEventPump&> mPump;
};
namespace llcoro
{
/**
* Yield control from a coroutine for one "mainloop" tick. If your coroutine
* runs without suspending for nontrivial time, sprinkle in calls to this
* function to avoid stalling the rest of the viewer processing.
*/
void suspend();
/**
* Yield control from a coroutine for at least the specified number of seconds
*/
void suspendUntilTimeout(float seconds);
/**
* Post specified LLSD event on the specified LLEventPump, then suspend 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 = suspendUntilEventOn(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 suspendUntilEventOn() is
* entered. Therefore, the coroutine completely misses an immediate reply
* event, making it suspend indefinitely.
*
* By contrast, postAndSuspend() listens on the @a replyPump @em before posting
* the specified LLSD event on the specified @a requestPump.
*
* @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 postAndSuspend() will listen for a
* reply. Pass either the LLEventPump& or its string name. The calling
* coroutine will suspend 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>.
*/
LLSD postAndSuspend(const LLSD& event, const LLEventPumpOrPumpName& requestPump,
const LLEventPumpOrPumpName& replyPump, const LLSD& replyPumpNamePath=LLSD());
/// Wait for the next event on the specified LLEventPump. Pass either the
/// LLEventPump& or its string name.
inline
LLSD suspendUntilEventOn(const LLEventPumpOrPumpName& pump)
{
// This is now a convenience wrapper for postAndSuspend().
return postAndSuspend(LLSD(), LLEventPumpOrPumpName(), pump);
}
/// Like postAndSuspend(), but if we wait longer than @a timeout seconds,
/// stop waiting and return @a timeoutResult instead.
LLSD postAndSuspendWithTimeout(const LLSD& event,
const LLEventPumpOrPumpName& requestPump,
const LLEventPumpOrPumpName& replyPump,
const LLSD& replyPumpNamePath,
F32 timeout, const LLSD& timeoutResult);
/// Suspend the coroutine until an event is fired on the identified pump
/// or the timeout duration has elapsed. If the timeout duration
/// elapses the specified LLSD is returned.
inline
LLSD suspendUntilEventOnWithTimeout(const LLEventPumpOrPumpName& suspendPumpOrName,
F32 timeoutin, const LLSD &timeoutResult)
{
return postAndSuspendWithTimeout(LLSD(), // event
LLEventPumpOrPumpName(), // requestPump
suspendPumpOrName, // replyPump
LLSD(), // replyPumpNamePath
timeoutin,
timeoutResult);
}
} // namespace llcoro
/**
* 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 suspend() method to suspend 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.
*/
LLSD suspend()
{
return llcoro::suspendUntilEventOn(mPump);
}
LLSD postAndSuspend(const LLSD& event, const LLEventPumpOrPumpName& requestPump,
const LLSD& replyPumpNamePath=LLSD())
{
return llcoro::postAndSuspend(event, requestPump, mPump, replyPumpNamePath);
}
private:
LLEventStream mPump;
};
#endif /* ! defined(LL_LLEVENTCORO_H) */
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