Added an example program for the bridge object.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%404278

examples/CMakeLists.txt

@@ -42,6 +42,7 @@ ENDMACRO()
 add_example(bayes_net_ex)
 add_example(bayes_net_from_disk_ex)
 add_example(bayes_net_gui_ex)
+add_example(bridge_ex)
 add_example(compress_stream_ex)
 add_example(config_reader_ex)
 add_example(custom_trainer_ex)

examples/bridge_ex.cpp

+// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
+
+
+/*
+    This is an example showing how to use the bridge object from from the 
+    dlib C++ Library to send messages via TCP/IP.
+
+    In particular, this example will walk you through four progressively
+    more complex use cases of the bridge object.  Note that this example
+    program assumes you are already familiar with the pipe object and at
+    least the contents of the pipe_ex_2.cpp example program.
+*/
+
+
+#include "dlib/bridge.h"
+#include "dlib/type_safe_union.h"
+#include <iostream>
+
+using namespace dlib;
+using namespace std;
+
+// ----------------------------------------------------------------------------------------
+
+void run_example_1();
+void run_example_2();
+void run_example_3();
+void run_example_4();
+
+// ----------------------------------------------------------------------------------------
+
+int main()
+{
+    run_example_1();
+    run_example_2();
+    run_example_3();
+    run_example_4();
+}
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+void run_example_1(
+)
+{
+    cout << "\n ---- Running example 1 ---- " << endl;
+
+    /*
+        The idea of the bridge is basically to allow two different dlib::pipe objects
+        to be connected together via a TCP connection.  This is best illustrated by
+        the following short example.  In it we create two pipes, in and out.  When
+        an object is enqueued into the out pipe it will be automatically sent 
+        through a TCP connection and once received at the other end it will be 
+        inserted into the in pipe.
+    */
+    dlib::pipe<int> in(4), out(4);
+
+
+    // This bridge will listen on port 12345 for an incoming TCP connection.  Then
+    // it will read data from that connection and put it into the in pipe.
+    bridge b2(listen_on_port(12345), receive(in));
+
+    // This bridge will initiate a TCP connection and then start dequeuing 
+    // objects from out and transmitting them over the connection.
+    bridge b1(connect_to_ip_and_port("127.0.0.1", 12345), transmit(out));
+
+    // As an aside, in a real program, each of these bridges and pipes would be in a 
+    // separate application.  But to make this example self contained they are both 
+    // right here.
+
+
+
+    // Now lets put some things into the out pipe
+    int value = 1;
+    out.enqueue(value);
+
+    value = 2;
+    out.enqueue(value);
+
+    value = 3;
+    out.enqueue(value);
+
+
+    // Now those 3 ints can be dequeued from the in pipe.  They will show up
+    // in the same order they were inserted into the out pipe.
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+}
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+void run_example_2(
+)
+{
+    cout << "\n ---- Running example 2 ---- " << endl;
+
+    /*
+        This example makes a simple echo server on port 12345.  When an object
+        is inserted into the out pipe it will be sent over a TCP connection, get 
+        put into the echo pipe and then immediately read out of the echo pipe and
+        sent back over the TCP connection where it will finally be placed into the in
+        pipe.
+    */
+
+    dlib::pipe<int> in(4), out(4), echo(4);
+
+    // Just like TCP connections, a bridge can send data both directions.  The directionality
+    // of a pipe is indicated by the receive() and transmit() type decorations.  Also, the order
+    // they are listed doesn't matter.
+    bridge echo_bridge(listen_on_port(12345), receive(echo), transmit(echo));
+
+    bridge b1(connect_to_ip_and_port("127.0.0.1", 12345), transmit(out), receive(in));
+
+
+    int value = 1;
+    out.enqueue(value);
+
+    value = 2;
+    out.enqueue(value);
+
+    value = 3;
+    out.enqueue(value);
+
+
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+    in.dequeue(value);
+    cout << "dequeued value: "<< value << endl;
+}
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+struct my_example_object
+{
+    /*
+        All objects passing though a dlib::bridge must be serializable.  This
+        means there must exist global functions called serialize() and deserialize()
+        which can convert an object into a bit stream and then reverse the process.
+
+        This example object illustrates how this is done.
+    */
+
+    int value;
+    std::string str;
+};
+
+void serialize (const my_example_object& item, std::ostream& out)
+{
+    /*
+        serialize() just needs to write the state of item to the output stream.
+        You can do this however you like.  Below, I'm using the serialize functions
+        for int and std::string which come with dlib.  But again, you can do whatever
+        you want here.
+    */
+    dlib::serialize(item.value, out);
+    dlib::serialize(item.str, out);
+}
+
+void deserialize (my_example_object& item, std::istream& in)
+{
+    /*
+        deserialize() is just the inverse of serialize().  Again, you can do
+        whatever you want here so long as it correctly reconstructs item.  This
+        also means that deserialize() must always consume as many bytes as serialize()
+        generates.
+    */
+    dlib::deserialize(item.value, in);
+    dlib::deserialize(item.str, in);
+}
+
+// ----------------------------------------------------------------------------------------
+
+void run_example_3(
+)
+{
+    cout << "\n ---- Running example 3 ---- " << endl;
+
+    /*
+        In this example we will just send ints and my_example_object objects
+        over a TCP connection.  Since we are sending more than one type of
+        object though a pipe we will need to use the type_safe_union.
+    */
+
+    typedef type_safe_union<int, my_example_object> tsu_type;
+
+    dlib::pipe<tsu_type> in(4), out(4);
+
+    // Note that we don't have to start the listening bridge first.  If b2
+    // fails to make a connection it will just keep trying until successful.
+    bridge b2(connect_to_ip_and_port("127.0.0.1", 12345), receive(in));
+    // We don't have to configure a bridge in it's constructor.  If it's 
+    // more convenient we can do so by calling reconfigure() instead.
+    bridge b1;
+    b1.reconfigure(listen_on_port(12345), transmit(out));
+
+    tsu_type msg;
+
+    msg = 1;
+    out.enqueue(msg);
+
+    msg = 2;
+    out.enqueue(msg);
+
+    msg.get<my_example_object>().value = 3;
+    msg.get<my_example_object>().str = "some string";
+    out.enqueue(msg);
+
+
+    // dequeue the three objects we sent and print them on the screen.
+    for (int i = 0; i < 3; ++i)
+    {
+        in.dequeue(msg);
+        if (msg.contains<int>())
+        {
+            cout << "dequeued int:    "<< msg.get<int>() << endl;
+        }
+        else if (msg.contains<my_example_object>())
+        {
+            cout << "dequeued struct: "<< msg.get<my_example_object>().value << "   " 
+                                       << msg.get<my_example_object>().str << endl;
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+void run_example_4(
+)
+{
+    cout << "\n ---- Running example 4 ---- " << endl;
+
+    /*
+        This final example is the same as example 3 except we will also now be getting 
+        status messages from the bridges.  These bridge_status messages tell us the 
+        state of the TCP connection associated with a bridge.  Is it connected or not?  
+        Who it is connected to?
+
+        The way you get these status messages is by ensuring that your receive pipe is 
+        capable of storing bridge_status objects.  If it is then the bridge will 
+        automatically insert bridge_status messages into your receive pipe whenever 
+        there is a status change. 
+
+        There are only two kinds of status changes.  The establishment of a connection 
+        or the closing of a connection.   Also, a connection which closes due to you 
+        calling clear(), reconfigure(), or destructing a bridge does not generate a 
+        status message since, in this case, you already know about it and just want 
+        the bridge to destroy itself as quickly as possible.
+    */
+
+
+    typedef type_safe_union<int, my_example_object, bridge_status> tsu_type;
+
+    dlib::pipe<tsu_type> in(4), out(4);
+    dlib::pipe<bridge_status> b1_status(4);
+
+    // setup both bridges to have receive pipes capable of holding bridge_status messages.
+    bridge b1(listen_on_port(12345), transmit(out), receive(b1_status));
+    bridge b2(connect_to_ip_and_port("127.0.0.1", 12345), receive(in));
+
+    tsu_type msg;
+    bridge_status bs;
+
+    // Once a connection is established it will generate a status message from each bridge. 
+    // Lets get those and print them.  
+    b1_status.dequeue(bs);
+    cout << "bridge 1 status: is_connected: " << boolalpha << bs.is_connected << endl;
+    cout << "bridge 1 status: foreign_ip:   " << bs.foreign_ip << endl;
+    cout << "bridge 1 status: foreign_port: " << bs.foreign_port << endl;
+
+    in.dequeue(msg);
+    bs = msg.get<bridge_status>();
+    cout << "bridge 2 status: is_connected: " << bs.is_connected << endl;
+    cout << "bridge 2 status: foreign_ip:   " << bs.foreign_ip << endl;
+    cout << "bridge 2 status: foreign_port: " << bs.foreign_port << endl;
+
+
+
+    msg = 1;
+    out.enqueue(msg);
+
+    msg = 2;
+    out.enqueue(msg);
+
+    msg.get<my_example_object>().value = 3;
+    msg.get<my_example_object>().str = "some string";
+    out.enqueue(msg);
+
+
+    // Read the 3 things we sent over the connection.
+    for (int i = 0; i < 3; ++i)
+    {
+        in.dequeue(msg);
+        if (msg.contains<int>())
+        {
+            cout << "dequeued int:    "<< msg.get<int>() << endl;
+        }
+        else if (msg.contains<my_example_object>())
+        {
+            cout << "dequeued struct: "<< msg.get<my_example_object>().value << "   " 
+                                       << msg.get<my_example_object>().str << endl;
+        }
+    }
+
+    // cause bridge 1 to shutdown completely.  This will close the connection and
+    // therefore bridge 2 will generate a status message indicating the connection
+    // just closed.
+    b1.clear();
+    in.dequeue(msg);
+    bs = msg.get<bridge_status>();
+    cout << "bridge 1 status: is_connected: " << bs.is_connected << endl;
+    cout << "bridge 1 status: foreign_ip:   " << bs.foreign_ip << endl;
+    cout << "bridge 1 status: foreign_port: " << bs.foreign_port << endl;
+}
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+