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/**
* @file llcallbacklist.cpp
* @brief A simple list of callback functions to call.
*
* $LicenseInfo:firstyear=2001&license=viewerlgpl$
* 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
* $/LicenseInfo$
*/
#include "lazyeventapi.h"
#include "llcallbacklist.h"
#include "llerror.h"
#include "llexception.h"
#include "llsdutil.h"
#include <boost/container_hash/hash.hpp>
#include <iomanip>
#include <vector>
//
// Member functions
//
/*****************************************************************************
* LLCallbackList
*****************************************************************************/
LLCallbackList::LLCallbackList()
{
// nothing
}
LLCallbackList::~LLCallbackList()
{
}
LLCallbackList::handle_t LLCallbackList::addFunction( callback_t func, void *data)
{
if (!func)
{
return {};
}
// only add one callback per func/data pair
//
if (containsFunction(func, data))
{
return {};
}
auto handle = addFunction([func, data]{ func(data); });
mLookup.emplace(callback_pair_t(func, data), handle);
return handle;
}
LLCallbackList::handle_t LLCallbackList::addFunction( const callable_t& func )
{
return mCallbackList.connect(func);
}
bool LLCallbackList::containsFunction( callback_t func, void *data)
{
return mLookup.find(callback_pair_t(func, data)) != mLookup.end();
}
bool LLCallbackList::deleteFunction( callback_t func, void *data)
{
auto found = mLookup.find(callback_pair_t(func, data));
if (found != mLookup.end())
{
mLookup.erase(found);
deleteFunction(found->second);
return true;
}
else
{
return false;
}
}
void LLCallbackList::deleteFunction( const handle_t& handle )
{
handle.disconnect();
}
void LLCallbackList::deleteAllFunctions()
{
mCallbackList = {};
mLookup.clear();
}
void LLCallbackList::callFunctions()
{
mCallbackList();
}
LLCallbackList::handle_t LLCallbackList::doOnIdleOneTime( const callable_t& func )
{
// connect_extended() passes the connection to the callback
return mCallbackList.connect_extended(
[func](const handle_t& handle)
{
handle.disconnect();
func();
});
}
LLCallbackList::handle_t LLCallbackList::doOnIdleRepeating( const bool_func_t& func )
{
return mCallbackList.connect_extended(
[func](const handle_t& handle)
{
if (func())
{
handle.disconnect();
}
});
}
/*****************************************************************************
* LL::Timers
*****************************************************************************/
namespace LL
{
Timers::Timers() {}
// Call a given callable once at specified timestamp.
Timers::handle_t Timers::scheduleAt(nullary_func_t callable, LLDate::timestamp time)
{
// tick() assumes you want to run periodically until you return true.
// Schedule a task that returns true after a single call.
return scheduleAtEvery(once(callable), time, 0);
}
// Call a given callable once after specified interval.
Timers::handle_t Timers::scheduleAfter(nullary_func_t callable, F32 seconds)
{
return scheduleEvery(once(callable), seconds);
}
// Call a given callable every specified number of seconds, until it returns true.
Timers::handle_t Timers::scheduleEvery(bool_func_t callable, F32 seconds)
{
return scheduleAtEvery(callable, now() + seconds, seconds);
}
Timers::handle_t Timers::scheduleAtEvery(bool_func_t callable,
LLDate::timestamp time, F32 interval)
{
// Pick token FIRST to store a self-reference in mQueue's managed node as
// well as in mMeta. Pre-increment to distinguish 0 from any live
// handle_t.
token_t token{ ++mToken };
// For the moment, store a default-constructed mQueue handle --
// we'll fill in later.
auto [iter, inserted] = mMeta.emplace(token,
Metadata{ queue_t::handle_type(), time, interval });
// It's important that our token is unique.
llassert(inserted);
// Remember whether this is the first entry in mQueue
bool first{ mQueue.empty() };
auto handle{ mQueue.emplace(callable, token, time) };
// Now that we have an mQueue handle_type, store it in mMeta entry.
iter->second.mHandle = handle;
if (first && ! mLive.connected())
{
// If this is our first entry, register for regular callbacks.
mLive = LLCallbackList::instance().doOnIdleRepeating([this]{ return tick(); });
}
// Make an Timers::handle_t from token.
return { token };
}
bool Timers::isRunning(handle_t timer) const
{
// A default-constructed timer isn't running.
// A timer we don't find in mMeta has fired or been canceled.
return timer && mMeta.find(timer.token) != mMeta.end();
}
F32 Timers::timeUntilCall(handle_t timer) const
{
MetaMap::const_iterator found;
if ((! timer) || (found = mMeta.find(timer.token)) == mMeta.end())
{
return 0.f;
}
else
{
return found->second.mTime - now();
}
}
// Cancel a future timer set by scheduleAt(), scheduleAfter(), scheduleEvery()
bool Timers::cancel(handle_t& timer)
{
// For exception safety, capture and clear timer before canceling.
// Once we've canceled this handle, don't retain the live handle.
const handle_t ctimer{ timer };
timer = handle_t();
return cancel(ctimer);
}
bool Timers::cancel(const handle_t& timer)
{
if (! timer)
{
return false;
}
// fibonacci_heap documentation does not address the question of what
// happens if you call erase() twice with the same handle. Is it a no-op?
// Does it invalidate the heap? Is it UB?
// Nor do we find any documented way to ask whether a given handle still
// tracks a valid heap node. That's why we capture all returned handles in
// mMeta and validate against that collection. What about the pop()
// call in tick()? How to map from the top() value back to the
// corresponding handle_t? That's why we store func_at::mToken.
// fibonacci_heap provides a pair of begin()/end() methods to iterate over
// all nodes (NOT in heap order), plus a function to convert from such
// iterators to handles. Without mMeta, that would be our only chance
// to validate.
auto found{ mMeta.find(timer.token) };
if (found == mMeta.end())
{
// we don't recognize this handle -- maybe the timer has already
// fired, maybe it was previously canceled.
return false;
}
// Funny case: what if the callback directly or indirectly reaches a
// cancel() call for its own handle?
if (found->second.mRunning)
{
// tick() has special logic to defer the actual deletion until the
// callback has returned
found->second.mCancel = true;
// this handle does in fact reference a live timer,
// which we're going to cancel when we get a chance
return true;
}
// Erase from mQueue the handle_type referenced by timer.token.
mQueue.erase(found->second.mHandle);
// before erasing the mMeta entry
mMeta.erase(found);
if (mQueue.empty())
{
// If that was the last active timer, unregister for callbacks.
//LLCallbackList::instance().deleteFunction(mLive);
// Since we're in the source file that knows the true identity of an
// LLCallbackList::handle_t, we don't even need to call instance().
mLive.disconnect();
}
return true;
}
void Timers::setTimeslice(F32 timeslice)
{
if (timeslice < MINIMUM_TIMESLICE)
{
// use stringize() so setprecision() affects only the temporary
// ostream, not the common logging ostream
LL_WARNS("Timers") << "LL::Timers::setTimeslice("
<< stringize(std::setprecision(4), timeslice)
<< ") less than "
<< stringize(std::setprecision(4), MINIMUM_TIMESLICE)
<< ", ignoring" << LL_ENDL;
}
else
{
mTimeslice = timeslice;
}
}
// RAII class to set specified variable to specified value
// only for the duration of containing scope
template <typename VAR, typename VALUE>
class TempSet
{
public:
TempSet(VAR& var, const VALUE& value):
mVar(var),
mOldValue(mVar)
{
mVar = value;
}
TempSet(const TempSet&) = delete;
TempSet& operator=(const TempSet&) = delete;
~TempSet()
{
mVar = mOldValue;
}
private:
VAR& mVar;
VALUE mOldValue;
};
bool Timers::tick()
{
// Fetch current time only on entry, even though running some mQueue task
// may take long enough that the next one after would become ready. We're
// sharing this thread with everything else, and there's a risk we might
// starve it if we have a sequence of tasks that take nontrivial time.
auto now{ LLDate::now().secondsSinceEpoch() };
auto cutoff{ now + mTimeslice };
// Capture tasks we've processed but that want to be rescheduled.
// Defer rescheduling them immediately to avoid getting stuck looping over
// a recurring task with a nonpositive interval.
std::vector<std::pair<MetaMap::iterator, func_at>> deferred;
while (! mQueue.empty())
{
auto& top{ mQueue.top() };
if (top.mTime > now)
{
// we've hit an entry that's still in the future:
// done with this tick()
break;
}
if (LLDate::now().secondsSinceEpoch() > cutoff)
{
// we still have ready tasks, but we've already eaten too much
// time this tick() -- defer until next tick()
break;
}
// Found a ready task. Look up its corresponding mMeta entry.
auto meta{ mMeta.find(top.mToken) };
llassert(meta != mMeta.end());
bool done;
{
// Mark our mMeta entry so we don't cancel this timer while its
// callback is running, but unmark it even in case of exception.
TempSet running(meta->second.mRunning, true);
// run the callback and capture its desire to end repetition
try
{
done = top.mFunc();
}
catch (...)
{
// Don't crash if a timer callable throws.
// But don't continue calling that callable, either.
done = true;
LOG_UNHANDLED_EXCEPTION("LL::Timers");
}
} // clear mRunning
// If mFunc() returned true (all done, stop calling me) or
// meta->mCancel (somebody tried to cancel this timer during the
// callback call), then we're done: clean up both entries.
if (done || meta->second.mCancel)
{
// remove the mMeta entry referencing this task
mMeta.erase(meta);
}
else
{
// mFunc returned false, and nobody asked to cancel:
// continue calling this task at a future time.
meta->second.mTime += meta->second.mInterval;
// capture this task to reschedule once we break loop
deferred.push_back({meta, top});
// update func_at's mTime to match meta's
deferred.back().second.mTime = meta->second.mTime;
}
// Remove the mQueue entry regardless, or we risk stalling the
// queue right here if we have a nonpositive interval.
mQueue.pop();
}
// Now reschedule any tasks that need to be rescheduled.
for (const auto& [meta, task] : deferred)
{
auto handle{ mQueue.push(task) };
// track this new mQueue handle_type
meta->second.mHandle = handle;
}
// If, after all the twiddling above, our queue ended up empty,
// stop calling every tick.
return mQueue.empty();
}
/*****************************************************************************
* TimersListener
*****************************************************************************/
class TimersListener: public LLEventAPI
{
public:
TimersListener(const LazyEventAPIParams& params): LLEventAPI(params) {}
// Forbid a script from requesting callbacks too quickly.
static constexpr LLSD::Real MINTIMER{ 1.0 };
void scheduleAfter(const LLSD& params);
void scheduleEvery(const LLSD& params);
LLSD cancel(const LLSD& params);
LLSD isRunning(const LLSD& params);
LLSD timeUntilCall(const LLSD& params);
private:
// We use the incoming reqid to distinguish different timers -- but reqid
// by itself is not unique! Each reqid is local to a calling script.
// Distinguish scripts by reply-pump name, then reqid within script.
// "Additional specializations for std::pair and the standard container
// types, as well as utility functions to compose hashes are available in
// boost::hash."
// https://en.cppreference.com/w/cpp/utility/hash
using HandleKey = std::pair<LLSD::String, LLSD::Integer>;
using HandleMap = std::unordered_map<HandleKey, Timers::temp_handle_t,
boost::hash<HandleKey>>;
HandleMap mHandles;
};
void TimersListener::scheduleAfter(const LLSD& params)
{
// Timer creation functions respond immediately with the reqid of the
// created timer, as well as later when the timer fires. That lets the
// requester invoke cancel, isRunning or timeUntilCall.
Response response(LLSD(), params);
LLSD::Real after{ params["after"] };
if (after < MINTIMER)
{
return response.error(stringize("after must be at least ", MINTIMER));
}
HandleKey key{ params["reply"], params["reqid"] };
mHandles.emplace(
key,
Timers::instance().scheduleAfter(
[this, params, key]
{
// we don't need any content save for the "reqid"
sendReply({}, params);
// ditch mHandles entry
mHandles.erase(key);
},
after));
}
void TimersListener::scheduleEvery(const LLSD& params)
{
// Timer creation functions respond immediately with the reqid of the
// created timer, as well as later when the timer fires. That lets the
// requester invoke cancel, isRunning or timeUntilCall.
Response response(LLSD(), params);
LLSD::Real every{ params["every"] };
if (every < MINTIMER)
{
return response.error(stringize("every must be at least ", MINTIMER));
}
mHandles.emplace(
HandleKey{ params["reply"], params["reqid"] },
Timers::instance().scheduleEvery(
[params, i=0]() mutable
{
// we don't need any content save for the "reqid"
sendReply(llsd::map("i", i++), params);
// we can't use a handshake -- always keep the ball rolling
return false;
},
every));
}
LLSD TimersListener::cancel(const LLSD& params)
{
auto found{ mHandles.find({params["reply"], params["id"]}) };
bool ok = false;
if (found != mHandles.end())
{
ok = true;
Timers::instance().cancel(found->second);
mHandles.erase(found);
}
return llsd::map("ok", ok);
}
LLSD TimersListener::isRunning(const LLSD& params)
{
auto found{ mHandles.find({params["reply"], params["id"]}) };
bool running = false;
if (found != mHandles.end())
{
running = Timers::instance().isRunning(found->second);
}
return llsd::map("running", running);
}
LLSD TimersListener::timeUntilCall(const LLSD& params)
{
auto found{ mHandles.find({params["reply"], params["id"]}) };
bool ok = false;
LLSD::Real remaining = 0;
if (found != mHandles.end())
{
ok = true;
remaining = Timers::instance().timeUntilCall(found->second);
}
return llsd::map("ok", ok, "remaining", remaining);
}
class TimersRegistrar: public LazyEventAPI<TimersListener>
{
using super = LazyEventAPI<TimersListener>;
using super::listener;
public:
TimersRegistrar():
super("Timers", "Provide access to viewer timer functionality.")
{
add("scheduleAfter",
R"-(Create a timer with ID "reqid". Post response after "after" seconds.)-",
&listener::scheduleAfter,
llsd::map("reqid", LLSD::Integer(), "after", LLSD::Real()));
add("scheduleEvery",
R"-(Create a timer with ID "reqid". Post response every "every" seconds
until cancel().)-",
&listener::scheduleEvery,
llsd::map("reqid", LLSD::Integer(), "every", LLSD::Real()));
add("cancel",
R"-(Cancel the timer with ID "id". Respond "ok"=true if "id" identifies
a live timer.)-",
&listener::cancel,
llsd::map("reqid", LLSD::Integer(), "id", LLSD::Integer()));
add("isRunning",
R"-(Query the timer with ID "id": respond "running"=true if "id" identifies
a live timer.)-",
&listener::isRunning,
llsd::map("reqid", LLSD::Integer(), "id", LLSD::Integer()));
add("timeUntilCall",
R"-(Query the timer with ID "id": if "id" identifies a live timer, respond
"ok"=true, "remaining"=seconds with the time left before timer expiry;
otherwise "ok"=false, "remaining"=0.)-",
&listener::timeUntilCall,
llsd::map("reqid", LLSD::Integer()));
}
};
static TimersRegistrar registrar;
} // namespace LL
|