Add example illustrating a custom handler invocation hook.

asio/boostify.pl

@@ -579,6 +579,7 @@ sub copy_examples
       "src/examples/http/server",
       "src/examples/http/server2",
       "src/examples/http/server3",
+      "src/examples/invocation",
       "src/examples/iostreams",
       "src/examples/multicast",
       "src/examples/serialization",

asio/src/Makefile.am

@@ -62,6 +62,7 @@ noinst_PROGRAMS = \
 	examples/http/server/http_server \
 	examples/http/server2/http_server \
 	examples/http/server3/http_server \
+	examples/invocation/prioritised_handlers \
 	examples/iostreams/daytime_client \
 	examples/iostreams/daytime_server \
 	examples/multicast/receiver \
@@ -268,6 +269,7 @@ else
 examples_http_server3_http_server_SOURCES += \
 	examples/http/server3/posix_main.cpp
 endif
+examples_invocation_prioritised_handlers_SOURCES = examples/invocation/prioritised_handlers.cpp
 examples_iostreams_daytime_client_SOURCES = examples/iostreams/daytime_client.cpp
 examples_iostreams_daytime_server_SOURCES = examples/iostreams/daytime_server.cpp
 examples_multicast_receiver_SOURCES = examples/multicast/receiver.cpp

asio/src/Makefile.bor

@@ -70,6 +70,7 @@ EXAMPLE_EXES = \
 	examples\http\server\http_server.exe \
 	examples\http\server2\http_server.exe \
 	examples\http\server3\http_server.exe \
+	examples\invocation\prioritised_handlers.exe \
 	examples\iostreams\daytime_client.exe \
 	examples\iostreams\daytime_server.exe \
 	examples\multicast\receiver.exe \

asio/src/Makefile.mgw

@@ -68,6 +68,7 @@ EXAMPLE_EXES = \
 	examples/echo/blocking_udp_echo_server.exe \
 	examples/http/client/async_client.exe \
 	examples/http/client/sync_client.exe \
+	examples/invocation/prioritised_handlers.exe \
 	examples/iostreams/daytime_client.exe \
 	examples/iostreams/daytime_server.exe \
 	examples/multicast/receiver.exe \

asio/src/Makefile.msc

@@ -101,6 +101,7 @@ EXAMPLE_EXES = \
 	examples\http\server\http_server.exe \
 	examples\http\server2\http_server.exe \
 	examples\http\server3\http_server.exe \
+	examples\invocation\prioritised_handlers.exe \
 	examples\iostreams\daytime_client.exe \
 	examples\iostreams\daytime_server.exe \
 	examples\multicast\receiver.exe \
@@ -158,6 +159,9 @@ check: $(UNIT_TEST_EXES)
 {examples\http\client}.cpp{examples\http\client}.exe:
 	cl -Fe$@ -Fo$(<:.cpp=.obj) $(CXXFLAGS) $(DEFINES) $< -link -opt:ref
 
+{examples\invocation}.cpp{examples\invocation}.exe:
+	cl -Fe$@ -Fo$(<:.cpp=.obj) $(CXXFLAGS) $(DEFINES) $< -link -opt:ref
+
 {examples\iostreams}.cpp{examples\iostreams}.exe:
 	cl -Fe$@ -Fo$(<:.cpp=.obj) $(CXXFLAGS) $(DEFINES) $< -link -opt:ref
 

asio/src/examples/invocation/prioritised_handlers.cpp

@@ -0,0 +1,147 @@
+//
+// prioritised_handlers.cpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2007 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include "asio.hpp"
+#include <boost/function.hpp>
+#include <iostream>
+#include <queue>
+
+class handler_priority_queue
+{
+public:
+  void add(int priority, boost::function<void()> function)
+  {
+    handlers_.push(queued_handler(priority, function));
+  }
+
+  void execute_all()
+  {
+    while (!handlers_.empty())
+    {
+      queued_handler handler = handlers_.top();
+      handler.execute();
+      handlers_.pop();
+    }
+  }
+
+  // A generic wrapper class for handlers to allow the invocation to be hooked.
+  template <typename Handler>
+  class wrapped_handler
+  {
+  public:
+    wrapped_handler(handler_priority_queue& q, int p, Handler h)
+      : queue_(q), priority_(p), handler_(h)
+    {
+    }
+
+    void operator()()
+    {
+      handler_();
+    }
+
+    template <typename Arg1>
+    void operator()(Arg1 arg1)
+    {
+      handler_(arg1);
+    }
+
+    template <typename Arg1, typename Arg2>
+    void operator()(Arg1 arg1, Arg2 arg2)
+    {
+      handler_(arg1, arg2);
+    }
+
+  //private:
+    handler_priority_queue& queue_;
+    int priority_;
+    Handler handler_;
+  };
+
+  template <typename Handler>
+  wrapped_handler<Handler> wrap(int priority, Handler handler)
+  {
+    return wrapped_handler<Handler>(*this, priority, handler);
+  }
+
+private:
+  class queued_handler
+  {
+  public:
+    queued_handler(int p, boost::function<void()> f)
+      : priority_(p), function_(f)
+    {
+    }
+
+    void execute()
+    {
+      function_();
+    }
+
+    friend bool operator<(const queued_handler& a,
+        const queued_handler& b)
+    {
+      return a.priority_ < b.priority_;
+    }
+
+  private:
+    int priority_;
+    boost::function<void()> function_;
+  };
+
+  std::priority_queue<queued_handler> handlers_;
+};
+
+// Custom invocation hook for wrapped handlers.
+template <typename Function, typename Handler>
+void asio_handler_invoke(Function f,
+    handler_priority_queue::wrapped_handler<Handler>* h)
+{
+  h->queue_.add(h->priority_, f);
+}
+
+//----------------------------------------------------------------------
+
+void high_priority_handler()
+{
+  std::cout << "High priority handler\n";
+}
+
+void middle_priority_handler()
+{
+  std::cout << "Middle priority handler\n";
+}
+
+void low_priority_handler()
+{
+  std::cout << "Low priority handler\n";
+}
+
+int main()
+{
+  asio::io_service io_service;
+
+  handler_priority_queue pri_queue;
+
+  io_service.post(pri_queue.wrap(0, low_priority_handler));
+  io_service.post(pri_queue.wrap(100, high_priority_handler));
+  io_service.post(pri_queue.wrap(42, middle_priority_handler));
+
+  while (io_service.run_one())
+  {
+    // The custom invocation hook adds the handlers to the priority queue
+    // rather than executing them from within the poll_one() call.
+    while (io_service.poll_one())
+      ;
+
+    pri_queue.execute_all();
+  }
+
+  return 0;
+}