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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) */