Extend LLEventAPI to directly call other functions & methods.

Until now, LLEventAPI has only been able to register functions specifically
accepting(const LLSD&). Typically you add a wrapper method to your LLEventAPI
subclass, register that, have it extract desired params from the incoming LLSD
and then call the actual function of interest.
With help from Alain, added new LLEventAPI::add() methods capable of
registering functions/methods with arbitrary parameter signatures. The code
uses boost::fusion magic to implicitly match incoming LLSD arguments to the
function's formal parameter list, bypassing the need for an explicit helper
method.
New add() methods caused an ambiguity with a previous convenience overload.
Removed that overload and fixed the one existing usage.
Replaced LLEventDispatcher::get() with try_call() -- it's no longer easy to
return a Callable for caller to call directly. But the one known use of that
feature simply used it to avoid fatal LL_ERRS on unknown function-name string,
hence the try_call() approach actually addresses that case more directly.
Added indra/common/lleventdispatcher_test.cpp to exercise new functionality.

1 files changed, 347 insertions, 27 deletions

diff --git a/indra/llcommon/lleventdispatcher.h b/indra/llcommon/lleventdispatcher.h
index dfffd59eb6..ce0fc7b585 100644
--- a/indra/llcommon/lleventdispatcher.h
+++ b/indra/llcommon/lleventdispatcher.h
@@ -27,18 +27,56 @@
  * 
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
+ *
+ * The invoker machinery that constructs a boost::fusion argument list for use
+ * with boost::fusion::invoke() is derived from
+ * http://www.boost.org/doc/libs/1_45_0/libs/function_types/example/interpreter.hpp
+ * whose license information is copied below:
+ *
+ * "(C) Copyright Tobias Schwinger
+ *
+ * Use modification and distribution are subject to the boost Software License,
+ * Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt)."
  */
 
 #if ! defined(LL_LLEVENTDISPATCHER_H)
 #define LL_LLEVENTDISPATCHER_H
 
+// nil is too generic a term to be allowed to be a global macro. In
+// particular, boost::fusion defines a 'class nil' (properly encapsulated in a
+// namespace) that a global 'nil' macro breaks badly.
+#if defined(nil)
+// Capture the value of the macro 'nil', hoping int is an appropriate type.
+static const int nil_(nil);
+// Now forget the macro.
+#undef nil
+// Finally, reintroduce 'nil' as a properly-scoped alias for the previously-
+// defined const 'nil_'. Make it static since otherwise it produces duplicate-
+// symbol link errors later.
+static const int& nil(nil_);
+#endif
+
 #include <string>
-#include <map>
+#include <boost/ptr_container/ptr_map.hpp>
 #include <boost/function.hpp>
 #include <boost/bind.hpp>
 #include <boost/iterator/transform_iterator.hpp>
+#include <boost/utility/enable_if.hpp>
+#include <boost/function_types/is_nonmember_callable_builtin.hpp>
+#include <boost/function_types/parameter_types.hpp>
+#include <boost/function_types/function_arity.hpp>
+#include <boost/type_traits/remove_cv.hpp>
+#include <boost/type_traits/remove_reference.hpp>
+#include <boost/fusion/include/push_back.hpp>
+#include <boost/fusion/include/cons.hpp>
+#include <boost/fusion/include/invoke.hpp>
+#include <boost/mpl/begin.hpp>
+#include <boost/mpl/end.hpp>
+#include <boost/mpl/next.hpp>
+#include <boost/mpl/deref.hpp>
 #include <typeinfo>
 #include "llevents.h"
+#include "llsdutil.h"
 
 class LLSD;
 
@@ -54,12 +92,18 @@ public:
     LLEventDispatcher(const std::string& desc, const std::string& key);
     virtual ~LLEventDispatcher();
 
-    /// Accept any C++ callable, typically a boost::bind() expression
+    /// @name Register functions accepting(const LLSD&)
+    //@{
+
+    /// Accept any C++ callable with the right signature, typically a
+    /// boost::bind() expression
     typedef boost::function<void(const LLSD&)> Callable;
 
     /**
-     * Register a @a callable by @a name. The optional @a required parameter
-     * is used to validate the structure of each incoming event (see
+     * Register a @a callable by @a name. The passed @a callable accepts a
+     * single LLSD value and uses it in any way desired, e.g. extract
+     * parameters and call some other function. The optional @a required
+     * parameter is used to validate the structure of each incoming event (see
      * llsd_matches()).
      */
     void add(const std::string& name,
@@ -69,8 +113,9 @@ public:
 
     /**
      * Special case: a subclass of this class can pass an unbound member
-     * function pointer without explicitly specifying the
-     * <tt>boost::bind()</tt> expression.
+     * function pointer (of an LLEventDispatcher subclass) without explicitly
+     * specifying the <tt>boost::bind()</tt> expression. The passed @a method
+     * accepts a single LLSD value, presumably containing other parameters.
      */
     template <class CLASS>
     void add(const std::string& name,
@@ -81,7 +126,8 @@ public:
         addMethod<CLASS>(name, desc, method, required);
     }
 
-    /// Overload for both const and non-const methods
+    /// Overload for both const and non-const methods. The passed @a method
+    /// accepts a single LLSD value, presumably containing other parameters.
     template <class CLASS>
     void add(const std::string& name,
              const std::string& desc,
@@ -91,8 +137,10 @@ public:
         addMethod<CLASS>(name, desc, method, required);
     }
 
+/*==========================================================================*|
     /// Convenience: for LLEventDispatcher, not every callable needs a
-    /// documentation string.
+    /// documentation string. The passed @a callable accepts a single LLSD
+    /// value, presumably containing other parameters.
     template <typename CALLABLE>
     void add(const std::string& name,
              CALLABLE callable,
@@ -100,6 +148,92 @@ public:
     {
         add(name, "", callable, required);
     }
+|*==========================================================================*/
+
+    //@}
+
+    /// @name Register functions with arbitrary param lists
+    //@{
+
+    /**
+     * Register a free function with arbitrary parameters. (This also works
+     * for static class methods.)
+     *
+     * When calling this name, pass an LLSD::Array. Each entry in turn will be
+     * converted to the corresponding parameter type using LLSDParam.
+     */
+    template<typename Function>
+    typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function>
+                               >::type add(const std::string& name,
+                                           const std::string& desc,
+                                           Function f);
+
+    /**
+     * Register a nonstatic class method with arbitrary parameters.
+     *
+     * To cover cases such as a method on an LLSingleton we don't yet want to
+     * instantiate, instead of directly storing an instance pointer, accept a
+     * nullary callable returning a pointer/reference to the desired class
+     * instance. If you already have an instance in hand,
+     * boost::lambda::var(instance) or boost::lambda::constant(instance_ptr)
+     * produce suitable callables.
+     *
+     * When calling this name, pass an LLSD::Array. Each entry in turn will be
+     * converted to the corresponding parameter type using LLSDParam.
+     */
+    template<typename Method, typename InstanceGetter>
+    typename boost::enable_if< boost::function_types::is_member_function_pointer<Method>
+                               >::type add(const std::string& name,
+                                           const std::string& desc,
+                                           Method f,
+                                           const InstanceGetter& getter);
+
+    /**
+     * Register a free function with arbitrary parameters. (This also works
+     * for static class methods.)
+     *
+     * Pass an LLSD::Array of parameter names, and optionally another
+     * LLSD::Array of default parameter values, a la LLSDArgsMapper.
+     *
+     * When calling this name, pass an LLSD::Map. We will internally generate
+     * an LLSD::Array using LLSDArgsMapper and then convert each entry in turn
+     * to the corresponding parameter type using LLSDParam.
+     */
+    template<typename Function>
+    typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function>
+                               >::type add(const std::string& name,
+                                           const std::string& desc,
+                                           Function f,
+                                           const LLSD& params,
+                                           const LLSD& defaults=LLSD());
+
+    /**
+     * Register a nonstatic class method with arbitrary parameters.
+     *
+     * To cover cases such as a method on an LLSingleton we don't yet want to
+     * instantiate, instead of directly storing an instance pointer, accept a
+     * nullary callable returning a pointer/reference to the desired class
+     * instance. If you already have an instance in hand,
+     * boost::lambda::var(instance) or boost::lambda::constant(instance_ptr)
+     * produce suitable callables.
+     *
+     * Pass an LLSD::Array of parameter names, and optionally another
+     * LLSD::Array of default parameter values, a la LLSDArgsMapper.
+     *
+     * When calling this name, pass an LLSD::Map. We will internally generate
+     * an LLSD::Array using LLSDArgsMapper and then convert each entry in turn
+     * to the corresponding parameter type using LLSDParam.
+     */
+    template<typename Method, typename InstanceGetter>
+    typename boost::enable_if< boost::function_types::is_member_function_pointer<Method>
+                               >::type add(const std::string& name,
+                                           const std::string& desc,
+                                           Method f,
+                                           const InstanceGetter& getter,
+                                           const LLSD& params,
+                                           const LLSD& defaults=LLSD());
+
+    //@}    
 
     /// Unregister a callable
     bool remove(const std::string& name);
@@ -109,12 +243,25 @@ public:
     /// the @a required prototype specified at add() time, die with LL_ERRS.
     void operator()(const std::string& name, const LLSD& event) const;
 
+    /// Call a registered callable with an explicitly-specified name and
+    /// return <tt>true</tt>. If no such callable exists, return
+    /// <tt>false</tt>. If the @a event fails to match the @a required
+    /// prototype specified at add() time, die with LL_ERRS.
+    bool try_call(const std::string& name, const LLSD& event) const;
+
     /// Extract the @a key value from the incoming @a event, and call the
     /// callable whose name is specified by that map @a key. If no such
     /// callable exists, die with LL_ERRS. If the @a event fails to match the
     /// @a required prototype specified at add() time, die with LL_ERRS.
     void operator()(const LLSD& event) const;
 
+    /// Extract the @a key value from the incoming @a event, call the callable
+    /// whose name is specified by that map @a key and return <tt>true</tt>.
+    /// If no such callable exists, return <tt>false</tt>. If the @a event
+    /// fails to match the @a required prototype specified at add() time, die
+    /// with LL_ERRS.
+    bool try_call(const LLSD& event) const;
+
     /// @name Iterate over defined names
     //@{
     typedef std::pair<std::string, std::string> NameDesc;
@@ -122,37 +269,44 @@ public:
 private:
     struct DispatchEntry
     {
-        DispatchEntry(const Callable& func, const std::string& desc, const LLSD& required):
-            mFunc(func),
-            mDesc(desc),
-            mRequired(required)
-        {}
-        Callable mFunc;
+        DispatchEntry(const std::string& desc);
+
         std::string mDesc;
-        LLSD mRequired;
+
+        virtual void call(const std::string& desc, const LLSD& event) const = 0;
+        virtual LLSD addMetadata(LLSD) const = 0;
     };
-    typedef std::map<std::string, DispatchEntry> DispatchMap;
+    typedef boost::ptr_map<std::string, DispatchEntry> DispatchMap;
 
 public:
     /// We want the flexibility to redefine what data we store per name,
     /// therefore our public interface doesn't expose DispatchMap iterators,
     /// or DispatchMap itself, or DispatchEntry. Instead we explicitly
     /// transform each DispatchMap item to NameDesc on dereferencing.
-    typedef boost::transform_iterator<NameDesc(*)(const DispatchMap::value_type&), DispatchMap::const_iterator> const_iterator;
+    typedef boost::transform_iterator<NameDesc(*)(DispatchMap::value_type), DispatchMap::iterator> const_iterator;
     const_iterator begin() const
     {
-        return boost::make_transform_iterator(mDispatch.begin(), makeNameDesc);
+        // Originally we used DispatchMap::const_iterator, which Just Worked
+        // when DispatchMap was a std::map. Now that it's a boost::ptr_map,
+        // using DispatchMap::const_iterator doesn't work so well: it
+        // dereferences to a pair<string, const T*>, whereas
+        // DispatchMap::value_type is just pair<string, T*>. Trying to pass a
+        // dereferenced iterator to the value_type didn't work because the
+        // compiler won't let you convert from const T* to plain T*. Changing
+        // our const_iterator definition above to be based on non-const
+        // DispatchMap::iterator works better, but of course we have to cast
+        // away the constness of mDispatch to use non-const iterator. (Sigh.)
+        return boost::make_transform_iterator(const_cast<DispatchMap&>(mDispatch).begin(),
+                                              makeNameDesc);
     }
     const_iterator end() const
     {
-        return boost::make_transform_iterator(mDispatch.end(), makeNameDesc);
+        // see begin() comments
+        return boost::make_transform_iterator(const_cast<DispatchMap&>(mDispatch).end(),
+                                              makeNameDesc);
     }
     //@}
 
-    /// Fetch the Callable for the specified name. If no such name was
-    /// registered, return an empty() Callable.
-    Callable get(const std::string& name) const;
-
     /// Get information about a specific Callable
     LLSD getMetadata(const std::string& name) const;
 
@@ -175,18 +329,184 @@ private:
         }
     }
     void addFail(const std::string& name, const std::string& classname) const;
-    /// try to dispatch, return @c true if success
-    bool attemptCall(const std::string& name, const LLSD& event) const;
 
     std::string mDesc, mKey;
     DispatchMap mDispatch;
 
-    static NameDesc makeNameDesc(const DispatchMap::value_type& item)
+    static NameDesc makeNameDesc(DispatchMap::value_type item)
     {
-        return NameDesc(item.first, item.second.mDesc);
+        return NameDesc(item.first, item.second->mDesc);
     }
+
+    struct LLSDDispatchEntry;
+    struct ParamsDispatchEntry;
+    struct ArrayParamsDispatchEntry;
+    struct MapParamsDispatchEntry;
+
+    // Step 2 of parameter analysis. Instantiating invoker<some_function_type>
+    // implicitly sets its From and To parameters to the (compile time) begin
+    // and end iterators over that function's parameter types.
+    template< typename Function
+              , class From = typename boost::mpl::begin< boost::function_types::parameter_types<Function> >::type
+              , class To   = typename boost::mpl::end< boost::function_types::parameter_types<Function> >::type
+              >
+    struct invoker;
+
+    // deliver LLSD arguments one at a time
+    typedef boost::function<LLSD()> args_source;
+    // obtain args from an args_source to build param list and call target
+    // function
+    typedef boost::function<void(const args_source&)> invoker_function;
+
+    template <typename Function>
+    invoker_function make_invoker(Function f);
+    template <typename Method, typename InstanceGetter>
+    invoker_function make_invoker(Method f, const InstanceGetter& getter);
+    void addArrayParamsDispatchEntry(const std::string& name,
+                                     const std::string& desc,
+                                     const invoker_function& invoker,
+                                     LLSD::Integer arity);
+    void addMapParamsDispatchEntry(const std::string& name,
+                                   const std::string& desc,
+                                   const invoker_function& invoker,
+                                   const LLSD& params,
+                                   const LLSD& defaults);
 };
 
+/*****************************************************************************
+*   LLEventDispatcher template implementation details
+*****************************************************************************/
+// Step 3 of parameter analysis, the recursive case.
+template<typename Function, class From, class To>
+struct LLEventDispatcher::invoker
+{
+    template<typename T>
+    struct remove_cv_ref
+        : boost::remove_cv< typename boost::remove_reference<T>::type >
+    { };
+
+    // apply() accepts an arbitrary boost::fusion sequence as args. It
+    // examines the next parameter type in the parameter-types sequence
+    // bounded by From and To, obtains the next LLSD object from the passed
+    // args_source and constructs an LLSDParam of appropriate type to try
+    // to convert the value. It then recurs with the next parameter-types
+    // iterator, passing the args sequence thus far.
+    template<typename Args>
+    static inline
+    void apply(Function func, const args_source& argsrc, Args const & args)
+    {
+        typedef typename boost::mpl::deref<From>::type arg_type;
+        typedef typename boost::mpl::next<From>::type next_iter_type;
+        typedef typename remove_cv_ref<arg_type>::type plain_arg_type;
+
+        invoker<Function, next_iter_type, To>::apply
+        ( func, argsrc, boost::fusion::push_back(args, LLSDParam<plain_arg_type>(argsrc())));
+    }
+
+    // Special treatment for instance (first) parameter of a non-static member
+    // function. Accept the instance-getter callable, calling that to produce
+    // the first args value. Since we know we're at the top of the recursion
+    // chain, we need not also require a partial args sequence from our caller.
+    template <typename InstanceGetter>
+    static inline
+    void method_apply(Function func, const args_source& argsrc, const InstanceGetter& getter)
+    {
+        typedef typename boost::mpl::next<From>::type next_iter_type;
+
+        // Instead of grabbing the first item from argsrc and making an
+        // LLSDParam of it, call getter() and pass that as the instance param.
+        invoker<Function, next_iter_type, To>::apply
+        ( func, argsrc, boost::fusion::push_back(boost::fusion::nil(), boost::ref(getter())));
+    }
+};
+
+// Step 4 of parameter analysis, the leaf case. When the general
+// invoker<Function, From, To> logic has advanced From until it matches To,
+// the compiler will pick this template specialization.
+template<typename Function, class To>
+struct LLEventDispatcher::invoker<Function,To,To>
+{
+    // the argument list is complete, now call the function
+    template<typename Args>
+    static inline
+    void apply(Function func, const args_source&, Args const & args)
+    {
+        boost::fusion::invoke(func, args);
+    }
+};
+
+template<typename Function>
+typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function> >::type
+LLEventDispatcher::add(const std::string& name, const std::string& desc, Function f)
+{
+    // Construct an invoker_function, a callable accepting const args_source&.
+    // Add to DispatchMap an ArrayParamsDispatchEntry that will handle the
+    // caller's LLSD::Array.
+    addArrayParamsDispatchEntry(name, desc, make_invoker(f),
+                                boost::function_types::function_arity<Function>::value);
+}
+
+template<typename Method, typename InstanceGetter>
+typename boost::enable_if< boost::function_types::is_member_function_pointer<Method> >::type
+LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
+                       const InstanceGetter& getter)
+{
+    // Subtract 1 from the compile-time arity because the getter takes care of
+    // the first parameter. We only need (arity - 1) additional arguments.
+    addArrayParamsDispatchEntry(name, desc, make_invoker(f, getter),
+                                boost::function_types::function_arity<Method>::value - 1);
+}
+
+template<typename Function>
+typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function> >::type
+LLEventDispatcher::add(const std::string& name, const std::string& desc, Function f,
+                       const LLSD& params, const LLSD& defaults)
+{
+    // See comments for previous is_nonmember_callable_builtin add().
+    addMapParamsDispatchEntry(name, desc, make_invoker(f), params, defaults);
+}
+
+template<typename Method, typename InstanceGetter>
+typename boost::enable_if< boost::function_types::is_member_function_pointer<Method> >::type
+LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
+                       const InstanceGetter& getter,
+                       const LLSD& params, const LLSD& defaults)
+{
+    addMapParamsDispatchEntry(name, desc, make_invoker(f, getter), params, defaults);
+}
+
+template <typename Function>
+LLEventDispatcher::invoker_function
+LLEventDispatcher::make_invoker(Function f)
+{
+    // Step 1 of parameter analysis, the top of the recursion. Passing a
+    // suitable f (see add()'s enable_if condition) to this method causes it
+    // to infer the function type; specifying that function type to invoker<>
+    // causes it to fill in the begin/end MPL iterators over the function's
+    // list of parameter types.
+    // While normally invoker::apply() could infer its template type from the
+    // boost::fusion::nil parameter value, here we must be explicit since
+    // we're boost::bind()ing it rather than calling it directly.
+    return boost::bind(&invoker<Function>::template apply<boost::fusion::nil>,
+                       f,
+                       _1,
+                       boost::fusion::nil());
+}
+
+template <typename Method, typename InstanceGetter>
+LLEventDispatcher::invoker_function
+LLEventDispatcher::make_invoker(Method f, const InstanceGetter& getter)
+{
+    // Use invoker::method_apply() to treat the instance (first) arg specially.
+    return boost::bind(&invoker<Method>::template method_apply<InstanceGetter>,
+                       f,
+                       _1,
+                       getter);
+}
+
+/*****************************************************************************
+*   LLDispatchListener
+*****************************************************************************/
 /**
  * Bundle an LLEventPump and a listener with an LLEventDispatcher. A class
  * that contains (or derives from) LLDispatchListener need only specify the