www.softbit.fi SOFTBIT

Components in Windows, some history and experiences. Thomas O’Rourke Softbit Oy / Managing Director 26 October 1999

Components in Windows, some history and experiences.

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Presentation 1. Introduction to Windows components and some historical background. 2. Some real examples from Softbit, and our experiences.

26 October 1999

Components in Windows, some history and experiences.

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Softbit Oy • An Elektrobit company, currently 20 persons. • Subcontract software development for communications technology companies. • Example customers, Nokia, Nemo, etc. • Specialize in C++ development and component technologies. 26 October 1999

Components in Windows, some history and experiences.

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Thomas O’Rourke

~1978-80 Played Advent. Sold first program for $2.00 1987-88 Exchange student, Univ of Oulu 1990 B.Sc. Computer Science (Minnesota) 1990-92 Elektrobit Oy (2 years) 1992 D.I. EE, Univ of Oulu. 1992-97 Microsoft Ltd. (Seattle, USA) 1997-… Softbit Oy 26 October 1999

Components in Windows, some history and experiences.

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Definition of Components • Binary code reuse: – Changes to component do not require clients to recompile. – Upgradable at runtime.

• Modern component technologies: – Polymorphism, – Location and discovery services, – Distribution, etc. 26 October 1999

Components in Windows, some history and experiences.

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Windows component history • Windows applications may use (or provide) many types of components, some big some small - I discuss these. – DLLs. – DLLs and C++. – COM objects and technologies: • COM fundamentals, • Automation, • OCX and ActiveX controls. 26 October 1999

Components in Windows, some history and experiences.

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DLLs C++ Name Mangling

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Components in Windows, some history and experiences.

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DLL - Dynamic Link Library • DLLs are the foundation of Windows and are still today. • Are components. • Take some time to load, but after first call they are as fast as functions. • All custom controls (buttons, trackbars) are in DLLs 26 October 1999

Components in Windows, some history and experiences.

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Principles Explicit linking: hInstance = LoadLibrary(“MyDll.dll”);// map DLL to addr pFunc = GetProcAddress(“MyDll.dll” “MyFunction”); (*pFunc)(parm1, parm2); //call func FreeLibrary(hInstance); // unmap dll

ImplicitLinking MyFunction(Parm1, Parm2) // remember to include MyDll.lib to link time! // Loading and unloading is UNCONTROLLABLE! -->Good Book: Advanced Windows by Jeffery Richter. ( MsPress) 26 October 1999

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C++ and DLLs • Can a C++ class “live in a DLL”, and can I use it in an application? • Yes. • How is this possible? • Name mangling.

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class __declspec(dllexport) Boat { int Turn(int Speed); int Turn(int one, int two); virtual int YouDoIt(int one) = 0; //virtual int Okay(int two); }; int Boat::Turn(int Speed) { Speed = Speed + 3; return Speed; } int Boat::Turn(int one, int two) { return 1; }

This directive tells linker to produce export symbols. (Microsoft specific)

// Taken from BOAT.LIB or BOAT.MAP // 0001:00000000 ??0Boat@@QAE@XZ 10001000 f Boat.obj //0001:00000020 ??0Boat@@QAE@ABV0@@Z 10001020 f Boat.obj //0001:00000040 ??4Boat@@QAEAAV0@ABV0@@Z 10001040 f Boat.obj //0001:00000050 ?Turn@Boat@@AAEHH@Z 10001050 f Boat.obj //0001:00000069 ?Turn@Boat@@AAEHHH@Z 10001069 f Boat.obj // ... // And if we take the comment away from the virtual we get the following: //Boat.obj : error LNK2001: unresolved external symbol // "private: virtual int __thiscall Boat::Okay(int)" (?Okay@Boat@@EAEHH@Z) 26 October 1999

Components in Windows, some history and experiences.

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Problems with DLLs • If shared by applications they must be put in common directory. • Name conflicts. • “C”style interface does not support instances, or grouping, etc.

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Components in Windows, some history and experiences.

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COM Automation OLE Controls (ActiveX Controls)

Good Book: Understanding ActiveX and OLE by David Chappell. (MsPress) 26 October 1999

Components in Windows, some history and experiences.

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Why was COM invented? • As a mechanism for OLE2. – Put Excel charts into Word, (linking and embedding). – Document centric computing, structured storage, etc. (Excel and word data in same document).

• DDE was a painful thing. • DLL’s were not enough! 26 October 1999

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COM • Big argument about mechanism for OLE2. • C++ was the new cool technology… • Simple solution: Use C++ Virtual function table format as basis for COM. “Bless Vtables as a binary interoperability standard.”

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C++ VTable

Class MyCar { virtual int AddRef () = 0; virtual int Release() = 0; virtual int QueryInterface(big_int ID, void **pInterface) = 0; virtual int TurnLeft(int Speed) = 0; virtual int TurnRight(int Speed) = 0; virtual int StartAccelerating(int Vel) = 0; virtual int StopAccelerating(int Vel) = 0; virtual int PressBrakes(int Kilograms, int Time) = 0; }; // THIS IS A REAL COM INTERFACE!! 26 October 1999

Components in Windows, some history and experiences.

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COM Objects Vtable: TurnLeft() TurnRight() Calling a COM interface

COM Object

ISomeInterface

IAmSecondInterface

UNDERSTAND: Everything happens through interfaces. 26 October 1999

Components in Windows, some history and experiences.

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Loading a COM Object COM system searches registry to determine which DLL houses your COM object. pFactory = GetClassFactory(GUID_CDMA_SYSTEM) pFactory->CreateInstance(GUID_PHONE_CONTROL, &pInterface); pInterface->MakePhoneCall(); pInterface->Release();

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Problems with Vtables • Very easy to use in C++ ;) • Painful to use in C :| • Impossible to use from Visual Basic :( – They are not dynamic. – VB Couldn’t handle types… Everything could be cast to everything else. – Vtables are not dynamic (can’t change at runtime). 26 October 1999

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Automation • Automation is built on top of COM. • Automation is based upon getting “Names and Ids”for functions, I.e. switch statements! • Automation defines its own object creation, own types, enumerators, even more than COM. 26 October 1999

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Automation in C++ • A COM object which supports Automation has some text and beep function char sTextOutFunc[128]; char sBeepFunc[128]; sTextOutFunc = GetNameofFunction(1) sBeepFunc = GetNameofFunction(2) CallFunc(sTextOutFunc, “Hello World”); CallFunc(sBeepFunc, “World”);

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Why was the OLE control architecture invented?

• As a COM-based replacement for VBx’s. (Visual Basic controls). • OLE Controls were to be the VB controls on steroids! • OCX’s could store data, had edit mode for design-time, broadcast capabilities, etc. 26 October 1999

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Microsoft discovers internet • Needed a plug-in to browser technology, what to do? • Rename OCX to ActiveX • Drop requirements for all those “silly” interfaces - like persistence and editing, etc.

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Some common mistakes with COM and ActiveX Controls

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Components in Windows, some history and experiences.

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COM Mistakes • Theory: if you want to make real component system every component must be in a separate DLL. • Reality: Loading DLLs is not very fast. Try loading 500 DLLs. • Experience: How you package your components is important! 26 October 1999

Components in Windows, some history and experiences.

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OCX button example • Theory: Every little UI element should be an ActiveX control. • Reality: ActiveX controls were expensive to create (not so bad nowadays).

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Wrapping a standard button Container Application (IExplorer) reflector FIRE_BUTTON_EVENT WM_COMMAND, BTN_CLICK WM_COMMAND

wnd OK

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Cancel

Components in Windows, some history and experiences.

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Examples of Windows Components from Softbit and our Experiences.

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Nemo’s TOM

Nemo Technologies 26 October 1999

Components in Windows, some history and experiences.

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www.softbit.fi User Interface

SOFTBIT Update state (after event) Drawing graphs Indication Events

one IMobilePh

Circular Buffer / Shared memory structure

High level commands

DataBuffer/ Shared memory structure

Mobile Phone

Phone State

IAdapter

IHandler

Handler (GSM)

SendMessage GetMessage

Adapter

Handlers Serial port

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Component technology: • Component technology implemented: – COM servers for “handlers”(DLL com object). – C++ classes in DLLs (using MFC).

• Components technology used: – ActiveX controls for mapping.

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Handlers (Com servers) • Simple message interpreters (no UI) • Encapsulates specifics of particular phone system (moving target) • Enables multi-site development (for example in the USA).

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C++ Classes • Application is made up of: – One main executable module containing main window, menu, etc. – 4 or 5 DLLs with most functionality • SerialPort • Graphing • MessageRouter •… . 26 October 1999

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ActiveX controls • Is messy to use from C++, MFC helps. • But… It gets the job done. • ActiveX controls are okay for objects that do some specific functions – displaying maps – displaying tables from databases, etc.

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Components in Windows, some history and experiences.

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Experience • Architecture is successful. • Simplicity of COM servers allowed many people to work on phone specific protocol stuff. • C++ DLL classes assisted: – Reducing compile dependencies – Allowing replacement if bugs were found. 26 October 1999

Components in Windows, some history and experiences.

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Demo: A C++ DLL component application

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PC-Suite for 9110 • Framework developed by PumaTech. • Contacts plug-in developed at Softbit – No source-code was ever exchanged!

• New plug-ins are possible – Own menus, icons, own helps, etc.

• NO COM required! • Supports dynamic loading, location of services, etc. 26 October 1999

Components in Windows, some history and experiences.

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Architecture • Uses C++ in DLLs with MFC support! – Called an “Extension DLL”

• Uses RUNTIME_TYPE information so that MFC can create instances as needed. • Restriction: only works with MFC applications, and doesn’t work distributed. 26 October 1999

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Architecture

SOFTBIT

MFC

(3)

(3)

CView (2) Component (DLL)

Main Window

Framework (EXE) (1)

(2) Callback function (3) Windows messages (4) Communicator handling

See: “Dynamic Runtime Objects: Building Applications Your Users Can Modify at Runtime”, July 1997 Microsoft Systems Journal. 26 October 1999

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Experience • Architecture is successful. • MFC Extension classes are nice: – Messages are passes through MFC message routing mechanisms, – Program in C++, – callbacks are simple.

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Components in Windows, some history and experiences.

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Experiences Conclusion

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Components in Windows, some history and experiences.

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C++ or COM? • Use C++ DLLs whenever possible to provide more robust applications, that are easier to develop, debug and maintain. • Use COM when you need to develop on multisites or need to involve external persons. 26 October 1999

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MFC Extension DLL’s • MFC is good. There are a lot of code examples available on internet. • Extension DLL’s make component writing easy and connects everything up nicely.

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COM Experience • COM basics are easy and work well. • Should your component work in any arbitrary container? Why? • Only use as much of COM as needed. – Don’t make yourself a giant OLE in place active document server! In place active is junk. No one can run Excel inside of Word anyway. 26 October 1999

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Design basics • Reduce dependencies – Avoid “Component soups”, unless necessary. – Consider layers, or façade patterns. – Group common functionality into packages.

• Isolate pieces – Isolate moving targets, and buggy spots in code - places where you don’t know everything. These are good candidates for components. 26 October 1999

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Design = tough questions • Consider all the alternatives. • DLLs, C++ extension DLLs, Sockets for cross process instead of DCOM, etc., Java, ...

• Make your architecture stand up to scrutiny. • Be realistic: understand your customer’s budget and time constraints - give them the components they need… (not more). 26 October 1999

Components in Windows, some history and experiences.

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Are components always better?

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Components in Windows, some history and experiences.

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Thomas O’Rourke +358 400308204 Softbit Oy www.softbit.fi

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Components in Windows, some history and experiences.

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Additional Notes and Automation example

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COM Books • “Effective COM”, by Don Box, is my favorite. – An objective view of COM – I totally agree with his statements • Dual interfaces are JUNK • Connection points are STUPID. • etc.

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Nemo’s SAM

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Automation-enable your application

• User’s can control your application. • They can use it to do things you have not thought of. • MFC provides good support for doing this. • User can use it from Visual Basic, etc.

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Quality Power level Number of dropped calls Average quality per dropped call

Commands Visual Basic program

Formatted data

Sam.exe (interprets measurement data. Does conversions, indexing, highly efficient)

Scenario: User wants to make a custom report in excel.

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Measurement data

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Exporting all Power Level values from SAM.exe into excel (Excel VB Code)

Dim SAM As AutoApplication Dim ret As Boolean Set SAM = New AutoApplication Set filecollection = SAM.Workspace.Item("files") Set datasetcollection = SAM.Workspace.Item("datasets") Set file = filecollection.Add ret = file.Load(“Filename and path”) Set dataset = datasetcollection.Add ret = dataset.SetFile(file.Id) dataset.Filter(“$EventType = MSP”) For counter = 1 To dataset.Count ActiveSheet.Cells(counter, 1).Value = dataset.GetEventParameters(counter) Next counter dataset.Close file.Close

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