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/**
* @file llcoros.h
* @author Nat Goodspeed
* @date 2009-06-02
* @brief Manage running boost::coroutine instances
*
* $LicenseInfo:firstyear=2009&license=viewergpl$
* Copyright (c) 2009, Linden Research, Inc.
* $/LicenseInfo$
*/
#if ! defined(LL_LLCOROS_H)
#define LL_LLCOROS_H
#include <boost/coroutine/coroutine.hpp>
#include "llsingleton.h"
#include <boost/ptr_container/ptr_map.hpp>
#include <string>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/preprocessor/iteration/local.hpp>
#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::coroutines::coroutine signature we use
typedef boost::coroutines::coroutine<void()> coro;
/// Canonical 'self' type
typedef coro::self self;
/**
* 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 other than 'self'!
* // Pass by value only!
* void myCoroutineMethod(LLCoros::self& self, std::string, LLSD);
* ...
* };
* ...
* std::string name = LLCoros::instance().launch(
* "mycoro", boost::bind(&MyClass::myCoroutineMethod, this, _1,
* "somestring", LLSD(17));
* @endcode
*
* Your function/method must accept LLCoros::self& as its first parameter.
* It can accept any other parameters you want -- but ONLY BY VALUE!
* Other reference parameters are a BAD IDEA! You Have Been Warned. See
* DEV-32777 comments for an explanation.
*
* Pass a callable that accepts the single LLCoros::self& parameter. It
* may work to pass a free function whose only parameter is 'self'; for
* all other cases use boost::bind(). Of course, for a non-static class
* method, the first parameter must be the class instance. Use the
* placeholder _1 for the 'self' parameter. 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.
*/
template <typename CALLABLE>
std::string launch(const std::string& prefix, const CALLABLE& callable)
{
return launchImpl(prefix, new coro(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, pass its @c self object to 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()).
*/
template <typename COROUTINE_SELF>
std::string getName(const COROUTINE_SELF& self) const
{
return getNameByID(self.get_id());
}
/// getName() by self.get_id()
std::string getNameByID(const void* self_id) const;
private:
friend class LLSingleton<LLCoros>;
LLCoros();
std::string launchImpl(const std::string& prefix, coro* newCoro);
std::string generateDistinctName(const std::string& prefix) const;
bool cleanup(const LLSD&);
typedef boost::ptr_map<std::string, coro> CoroMap;
CoroMap mCoros;
};
#endif /* ! defined(LL_LLCOROS_H) */
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