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Diffstat (limited to 'indra/llcommon/llcoros.h')
| -rw-r--r-- | indra/llcommon/llcoros.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/indra/llcommon/llcoros.h b/indra/llcommon/llcoros.h new file mode 100644 index 0000000000..6b07ba4105 --- /dev/null +++ b/indra/llcommon/llcoros.h @@ -0,0 +1,149 @@ +/** + * @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 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) */ |