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www.softbit.fi SOFTBIT Components in Windows, some history and experiences. Thomas ORourke Softbit Oy / Managing Director 26 October 1999 Components in Windows, some history and experiences. 1 www.softbit.fi SOFTBIT Presentation 1.

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26 October 1999 Components in Windows, some history and experiences. 1

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Components in Windows, some history and experiences.

Thomas O’Rourke Softbit Oy / Managing Director

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Presentation

  • 1. Introduction to Windows components

and some historical background.

  • 2. Some real examples from Softbit, and
  • ur 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.

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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

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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.

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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.
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DLLs C++ Name Mangling

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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

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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)
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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; } // 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)

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

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

COM Automation OLE Controls (ActiveX Controls)

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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!
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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!!

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COM Objects

COM Object ISomeInterface IAmSecondInterface Vtable: TurnLeft() TurnRight() UNDERSTAND: Everything happens through interfaces.

Calling a COM interface

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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).

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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.

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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.

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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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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!

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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

OK Cancel reflector

WM_COMMAND, BTN_CLICK WM_COMMAND FIRE_BUTTON_EVENT

wnd Container Application (IExplorer)

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Examples of Windows Components from Softbit and our Experiences.

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Nemo’s TOM

Nemo Technologies

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Handlers

Adapter Handler (GSM) IHandler Serial port IAdapter Mobile Phone I M

  • b

i l e P h

  • n

e User Interface High level commands Circular Buffer / Shared memory structure DataBuffer/ Shared memory structure Phone State Indication Events Update state (after event) SendMessage GetMessage Drawing graphs

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Component technology:

  • Component technology implemented:

– COM servers for “handlers” (DLL com

  • bject).

– 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
  • ….
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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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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.

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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.

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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.

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Architecture

Component (DLL) Framework (EXE) MFC (2) (1) (3)

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

CView Main Window (3)

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

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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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Experiences Conclusion

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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.

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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

  • ne can run Excel inside of Word anyway.
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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.

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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).

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Are components always better?

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

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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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Sam.exe (interprets measurement

  • data. Does conversions,

indexing, highly efficient) Measurement data Visual Basic program Formatted data

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

Commands

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

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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