Server Side JavaScript: Ajax.org O3
- 2. Our demo: Real-time c ollaborative city planner Changes are distributed using XMPP XMPP bot updates traffic patterns Runs in Javascript on the server Welcome!
- 3. What is O 3 ? Collection of C++ components, made available through Javascript API Runs on all major browsers, and all major operating systems Library to create scriptable C++ components
- 4. What is O 3 ? Comes in two flavors: O 3 client-side: Runs as plug-in in the browser Extends DOM API with O3 components Useful if you’re developing in the browser O 3 server-side: Runs as standalone application Uses Google’s V8 engine to run scripts Provides the same components
- 5. What is O 3 ? All O3 components are available on both the client and the server! To use O3 at the client, you need a plugin however…
- 6. What is O3? O3 Library consists of three parts: Component model Reflection layer Containers, algorithms, etc.
- 7. Component model Subset of Microsoft’s COM specification (as opposed to XPCOM, CORBA, etc.) Looks like this: o3_iid(iFoo, 0x3F2504E0, 0x4F89, 0x11D3, 0x9A, 0x0C, 0x03, 0x05, 0xE8, 0x2C, 0x33, 0x01); struct iFoo : iUnk { virtual void bar(int x) = 0; }; o3_cls(cFoo) struct cFoo : cUnk, iFoo { o3_begin_class(cUnk) o3_add_iface(iFoo) o3_end() };
- 8. Reflection layer Special interface: struct iScr : iUnk { int resolve(const char*); void invoke(iCtx* ctx, Access access, int id, int argc, Var* argv, Var* rval, Ex* ex); … }; Allows you to query C++ objects for their methods and properties! Indexed based because some script engines require this (i.e. IDispatch)
- 9. Containers, algorithms, etc. We don’t use STL (although you could!) Our containers have lots of useful features and optimizations: Stack allocation for small strings Copy-on write semantics Automatic UTF-8/UTF-16 conversion (not possible with STL) Vectors are scriptable as well! (using Array interface)
- 10. Writing components Writing O3 components is easy! All you need to do is add some tags: o3_get int value(); // getter o3_set int setValue(int value); // setter o3_fun int function(int x); // function Code generator will do the rest! (also written in Javascript)
- 11. Writing components We want our components to be as fast as possible! Immediate properties: o3_imm_get int foo; // read-only o3_imm_set int bar; // write-only o3_imm int value; // read/write No getters/setters are generated, properties are accessed directly.
- 12. Writing components We want to be able to load components on the fly! Extension properties: In C++: o3_ext(“cO3”) o3_fun static int test(int x); In Javascript: o3.loadModule(“test”); o3.test(3);
- 13. Dealing with async Use threads to implement asynchronous Javascript calls. Use message passing to implement callbacks This requires an explicit message loop on the server: while (true) o3.wait(); Not needed at the client! (We can hook into the browser message loop there…)
- 14. HTTP Component Based on XMLHttpRequest API Example: var http = o3.http(); http.onprogress = function(http) { if (http.bytesReceived > 10000) … } http.onreadystatechange = function(http) { if (http.readystate == http.COMPLETED) … } http.open(“GET”, “www.ajax.org”); http.send();
- 15. XML Component Based on XML DOM API Example: var xml = o3.xml(); var doc = xml.parseFromString(string); var element = doc.documentElement; for (var child = element.firstChild; child != element.lastChild; child = child.nextSibling) …
- 16. FS Component Example: var cwd = o3.cwd; var file = cwd.get(“test.txt”); file.onchange = function(file) { file.copy(cwd.get(“test.bak”)); } We’re working on other components as well! IMAGE SOCKET JS
- 17. Putting it together Wait for update from XMPP server (using HTTP) Parse XMPP data (using XML) Calculate traffic patterns (using trip generation) Notify server of changes (using HTTP)
- 18. Thank you!