331 lines
12 KiB
C++
331 lines
12 KiB
C++
/**
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* @file llcoros.h
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* @author Nat Goodspeed
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* @date 2009-06-02
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* @brief Manage running boost::coroutine instances
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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_LLCOROS_H)
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#define LL_LLCOROS_H
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#include <boost/dcoroutine/coroutine.hpp>
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#include <boost/dcoroutine/future.hpp>
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#include "llsingleton.h"
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#include <boost/ptr_container/ptr_map.hpp>
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#include <boost/function.hpp>
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#include <boost/thread/tss.hpp>
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#include <boost/noncopyable.hpp>
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#include <string>
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#include <stdexcept>
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#include "llcoro_get_id.h" // for friend declaration
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// forward-declare helper class
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namespace llcoro
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{
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class Suspending;
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}
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/**
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* Registry of named Boost.Coroutine instances
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*
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* The Boost.Coroutine library supports the general case of a coroutine
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* accepting arbitrary parameters and yielding multiple (sets of) results. For
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* such use cases, it's natural for the invoking code to retain the coroutine
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* instance: the consumer repeatedly calls into the coroutine, perhaps passing
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* new parameter values, prompting it to yield its next result.
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*
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* Our typical coroutine usage is different, though. For us, coroutines
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* provide an alternative to the @c Responder pattern. Our typical coroutine
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* has @c void return, invoked in fire-and-forget mode: the handler for some
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* user gesture launches the coroutine and promptly returns to the main loop.
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* The coroutine initiates some action that will take multiple frames (e.g. a
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* capability request), waits for its result, processes it and silently steals
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* away.
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*
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* This usage poses two (related) problems:
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*
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* # Who should own the coroutine instance? If it's simply local to the
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* handler code that launches it, return from the handler will destroy the
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* coroutine object, terminating the coroutine.
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* # Once the coroutine terminates, in whatever way, who's responsible for
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* cleaning up the coroutine object?
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*
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* LLCoros is a Singleton collection of currently-active coroutine instances.
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* Each has a name. You ask LLCoros to launch a new coroutine with a suggested
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* name prefix; from your prefix it generates a distinct name, registers the
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* new coroutine and returns the actual name.
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*
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* The name can be used to kill off the coroutine prematurely, if needed. It
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* can also provide diagnostic info: we can look up the name of the
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* currently-running coroutine.
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*
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* Finally, the next frame ("mainloop" event) after the coroutine terminates,
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* LLCoros will notice its demise and destroy it.
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*/
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class LL_COMMON_API LLCoros: public LLSingleton<LLCoros>
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{
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LLSINGLETON(LLCoros);
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public:
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/// Canonical boost::dcoroutines::coroutine signature we use
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typedef boost::dcoroutines::coroutine<void()> coro;
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/// Canonical callable type
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typedef boost::function<void()> callable_t;
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/**
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* Create and start running a new coroutine with specified name. The name
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* string you pass is a suggestion; it will be tweaked for uniqueness. The
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* actual name is returned to you.
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*
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* Usage looks like this, for (e.g.) two coroutine parameters:
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* @code
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* class MyClass
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* {
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* public:
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* ...
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* // Do NOT NOT NOT accept reference params!
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* // Pass by value only!
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* void myCoroutineMethod(std::string, LLSD);
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* ...
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* };
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* ...
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* std::string name = LLCoros::instance().launch(
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* "mycoro", boost::bind(&MyClass::myCoroutineMethod, this,
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* "somestring", LLSD(17));
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* @endcode
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*
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* Your function/method can accept any parameters you want -- but ONLY BY
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* VALUE! Reference parameters are a BAD IDEA! You Have Been Warned. See
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* DEV-32777 comments for an explanation.
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*
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* Pass a nullary callable. It works to directly pass a nullary free
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* function (or static method); for all other cases use boost::bind(). Of
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* course, for a non-static class method, the first parameter must be the
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* class instance. Any other parameters should be passed via the bind()
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* expression.
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*
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* launch() tweaks the suggested name so it won't collide with any
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* existing coroutine instance, creates the coroutine instance, registers
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* it with the tweaked name and runs it until its first wait. At that
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* point it returns the tweaked name.
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*/
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std::string launch(const std::string& prefix, const callable_t& callable);
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/**
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* Abort a running coroutine by name. Normally, when a coroutine either
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* runs to completion or terminates with an exception, LLCoros quietly
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* cleans it up. This is for use only when you must explicitly interrupt
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* one prematurely. Returns @c true if the specified name was found and
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* still running at the time.
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*/
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bool kill(const std::string& name);
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/**
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* From within a coroutine, look up the (tweaked) name string by which
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* this coroutine is registered. Returns the empty string if not found
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* (e.g. if the coroutine was launched by hand rather than using
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* LLCoros::launch()).
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*/
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std::string getName() const;
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/// for delayed initialization
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void setStackSize(S32 stacksize);
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/// for delayed initialization
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void printActiveCoroutines();
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/// get the current coro::self& for those who really really care
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static coro::self& get_self();
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/**
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* Most coroutines, most of the time, don't "consume" the events for which
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* they're suspending. This way, an arbitrary number of listeners (whether
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* coroutines or simple callbacks) can be registered on a particular
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* LLEventPump, every listener responding to each of the events on that
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* LLEventPump. But a particular coroutine can assert that it will consume
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* each event for which it suspends. (See also llcoro::postAndSuspend(),
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* llcoro::VoidListener)
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*/
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static void set_consuming(bool consuming);
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static bool get_consuming();
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/**
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* RAII control of the consuming flag
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*/
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class OverrideConsuming
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{
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public:
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OverrideConsuming(bool consuming):
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mPrevConsuming(get_consuming())
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{
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set_consuming(consuming);
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}
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~OverrideConsuming()
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{
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set_consuming(mPrevConsuming);
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}
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private:
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bool mPrevConsuming;
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};
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/**
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* Please do NOT directly use boost::dcoroutines::future! It is essential
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* to maintain the "current" coroutine at every context switch. This
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* Future wraps the essential boost::dcoroutines::future functionality
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* with that maintenance.
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*/
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template <typename T>
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class Future;
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private:
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friend class llcoro::Suspending;
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friend llcoro::id llcoro::get_id();
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std::string generateDistinctName(const std::string& prefix) const;
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bool cleanup(const LLSD&);
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struct CoroData;
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static void no_cleanup(CoroData*);
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#if LL_WINDOWS
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static void winlevel(const callable_t& callable);
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#endif
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static void toplevel(coro::self& self, CoroData* data, const callable_t& callable);
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static CoroData& get_CoroData(const std::string& caller);
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S32 mStackSize;
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// coroutine-local storage, as it were: one per coro we track
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struct CoroData
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{
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CoroData(CoroData* prev, const std::string& name,
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const callable_t& callable, S32 stacksize);
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// The boost::dcoroutines library supports asymmetric coroutines. Every
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// time we context switch out of a coroutine, we pass control to the
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// previously-active one (or to the non-coroutine stack owned by the
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// thread). So our management of the "current" coroutine must be able to
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// restore the previous value when we're about to switch away.
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CoroData* mPrev;
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// tweaked name of the current coroutine
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const std::string mName;
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// the actual coroutine instance
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LLCoros::coro mCoro;
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// set_consuming() state
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bool mConsuming;
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// When the dcoroutine library calls a top-level callable, it implicitly
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// passes coro::self& as the first parameter. All our consumer code used
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// to explicitly pass coro::self& down through all levels of call stack,
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// because at the leaf level we need it for context-switching. But since
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// coroutines are based on cooperative switching, we can cause the
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// top-level entry point to stash a pointer to the currently-running
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// coroutine, and manage it appropriately as we switch out and back in.
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// That eliminates the need to pass it as an explicit parameter down
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// through every level, which is unfortunately viral in nature. Finding it
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// implicitly rather than explicitly allows minor maintenance in which a
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// leaf-level function adds a new async I/O call that suspends the calling
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// coroutine, WITHOUT having to propagate coro::self& through every
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// function signature down to that point -- and of course through every
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// other caller of every such function.
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LLCoros::coro::self* mSelf;
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F64 mCreationTime; // since epoch
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};
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typedef boost::ptr_map<std::string, CoroData> CoroMap;
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CoroMap mCoros;
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// Identify the current coroutine's CoroData. Use a little helper class so
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// a caller can either use a temporary instance, or instantiate a named
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// variable and access it multiple times.
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class Current
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{
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public:
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Current();
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operator LLCoros::CoroData*() { return get(); }
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LLCoros::CoroData* operator->() { return get(); }
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LLCoros::CoroData* get() { return mCurrent->get(); }
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void reset(LLCoros::CoroData* ptr) { mCurrent->reset(ptr); }
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private:
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boost::thread_specific_ptr<LLCoros::CoroData>* mCurrent;
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};
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};
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namespace llcoro
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{
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/// Instantiate one of these in a block surrounding any leaf point when
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/// control literally switches away from this coroutine.
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class Suspending: boost::noncopyable
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{
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public:
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Suspending();
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~Suspending();
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private:
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LLCoros::CoroData* mSuspended;
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};
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} // namespace llcoro
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template <typename T>
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class LLCoros::Future
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{
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typedef boost::dcoroutines::future<T> dfuture;
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public:
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Future():
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mFuture(get_self())
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{}
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typedef typename boost::dcoroutines::make_callback_result<dfuture>::type callback_t;
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callback_t make_callback()
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{
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return boost::dcoroutines::make_callback(mFuture);
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}
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#ifndef LL_LINUX
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explicit
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#endif
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operator bool() const
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{
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return bool(mFuture);
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}
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bool operator!() const
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{
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return ! mFuture;
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}
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T get()
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{
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// instantiate Suspending to manage the "current" coroutine
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llcoro::Suspending suspended;
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return *mFuture;
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}
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private:
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dfuture mFuture;
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};
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#endif /* ! defined(LL_LLCOROS_H) */
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