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/**
* @file llcoros.h
* @author Nat Goodspeed
* @date 2009-06-02
* @brief Manage running boost::coroutine instances
*
* $LicenseInfo:firstyear=2009&license=viewerlgpl$
* 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_LLCOROS_H)
#define LL_LLCOROS_H
#include <boost/dcoroutine/coroutine.hpp>
#include "llsingleton.h"
#include <boost/ptr_container/ptr_map.hpp>
#include <boost/function.hpp>
#include <string>
#include <stdexcept>
/**
* Registry of named Boost.Coroutine instances
*
* The Boost.Coroutine library supports the general case of a coroutine
* accepting arbitrary parameters and yielding multiple (sets of) results. For
* such use cases, it's natural for the invoking code to retain the coroutine
* instance: the consumer repeatedly calls into the coroutine, perhaps passing
* new parameter values, prompting it to yield its next result.
*
* Our typical coroutine usage is different, though. For us, coroutines
* provide an alternative to the @c Responder pattern. Our typical coroutine
* has @c void return, invoked in fire-and-forget mode: the handler for some
* user gesture launches the coroutine and promptly returns to the main loop.
* The coroutine initiates some action that will take multiple frames (e.g. a
* capability request), waits for its result, processes it and silently steals
* away.
*
* This usage poses two (related) problems:
*
* # Who should own the coroutine instance? If it's simply local to the
* handler code that launches it, return from the handler will destroy the
* coroutine object, terminating the coroutine.
* # Once the coroutine terminates, in whatever way, who's responsible for
* cleaning up the coroutine object?
*
* LLCoros is a Singleton collection of currently-active coroutine instances.
* Each has a name. You ask LLCoros to launch a new coroutine with a suggested
* name prefix; from your prefix it generates a distinct name, registers the
* new coroutine and returns the actual name.
*
* The name can be used to kill off the coroutine prematurely, if needed. It
* can also provide diagnostic info: we can look up the name of the
* currently-running coroutine.
*
* Finally, the next frame ("mainloop" event) after the coroutine terminates,
* LLCoros will notice its demise and destroy it.
*/
class LL_COMMON_API LLCoros: public LLSingleton<LLCoros>
{
public:
/// Canonical boost::dcoroutines::coroutine signature we use
typedef boost::dcoroutines::coroutine<void()> coro;
/// Canonical callable type
typedef boost::function<void()> callable_t;
/**
* Create and start running a new coroutine with specified name. The name
* string you pass is a suggestion; it will be tweaked for uniqueness. The
* actual name is returned to you.
*
* Usage looks like this, for (e.g.) two coroutine parameters:
* @code
* class MyClass
* {
* public:
* ...
* // Do NOT NOT NOT accept reference params!
* // Pass by value only!
* void myCoroutineMethod(std::string, LLSD);
* ...
* };
* ...
* std::string name = LLCoros::instance().launch(
* "mycoro", boost::bind(&MyClass::myCoroutineMethod, this,
* "somestring", LLSD(17));
* @endcode
*
* Your function/method can accept any parameters you want -- but ONLY BY
* VALUE! Reference parameters are a BAD IDEA! You Have Been Warned. See
* DEV-32777 comments for an explanation.
*
* Pass a nullary callable. It works to directly pass a nullary free
* function (or static method); for all other cases use boost::bind(). Of
* course, for a non-static class method, the first parameter must be the
* class instance. Any other parameters should be passed via the bind()
* expression.
*
* launch() tweaks the suggested name so it won't collide with any
* existing coroutine instance, creates the coroutine instance, registers
* it with the tweaked name and runs it until its first wait. At that
* point it returns the tweaked name.
*/
std::string launch(const std::string& prefix, const callable_t& callable);
/**
* Abort a running coroutine by name. Normally, when a coroutine either
* runs to completion or terminates with an exception, LLCoros quietly
* cleans it up. This is for use only when you must explicitly interrupt
* one prematurely. Returns @c true if the specified name was found and
* still running at the time.
*/
bool kill(const std::string& name);
/**
* From within a coroutine, look up the (tweaked) name string by which
* this coroutine is registered. Returns the empty string if not found
* (e.g. if the coroutine was launched by hand rather than using
* LLCoros::launch()).
*/
std::string getName() const;
/// for delayed initialization
void setStackSize(S32 stacksize);
private:
LLCoros();
friend class LLSingleton<LLCoros>;
std::string generateDistinctName(const std::string& prefix) const;
bool cleanup(const LLSD&);
S32 mStackSize;
typedef boost::ptr_map<std::string, coro> CoroMap;
CoroMap mCoros;
};
namespace llcoro
{
/// get the current coro::self& for those who really really care
LLCoros::coro::self& get_self();
/// Instantiate one of these in a block surrounding any leaf point when
/// control literally switches away from this coroutine.
class Suspending
{
public:
Suspending();
~Suspending();
private:
LLCoros::coro::self* mSuspended;
};
} // namespace llcoro
#endif /* ! defined(LL_LLCOROS_H) */
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