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Often such applications do not form part of a ROM andare installed onto a device after it has been created in a factory.Base portproviderA company that provides the base port required to get Symbian OS workingon specific device hardware.BinarycompatibilityThis is less restrictive than full compatibility in that it states only that a clientexecutable does not need to be re-compiled for it to work with all versionsof the binary compatible executable.CompatibilitySoftware is said to be compatible if the clients of one version of the softwarecan also be run on all other versions of the software without any changesbeing needed to the clients.ComponentA block of code that performs a particular function at an ‘interesting’ levelof functionality.CPMCommunication provider module.Device creatorA developer of software that is integrated into a ROM during devicemanufacture.
Device creators most commonly work for Symbian, a UIvendor or a base port provider but could also be one of their suppliers.DLL loadingruleA process can only load a DLL if that DLL has been trusted with at least thecapabilities that the process has.xxGLOSSARYWordDefinitionDRMDigital rights management (DRM) refers to technologies used by publishersand copyright holders to control access to and usage of digital media.EphemeralresourcesResources such as CPU cycles and battery power are ephemeral. Their keytrait is that you can’t hold on to them or reserve them for your own use.They’re there but you can’t keep a grip on them whether you use them ornot.ExecutableA file whose contents are meant to be interpreted as a program by acomputer.
Not just EXE files but DLLs and other file types as well.FrameworkA framework provides a reusable design for a software system or subsystem.It is expressed as a set of abstract classes and the way their instances collaborate, with the intent of facilitating software development by allowingdevelopers to spend more time on meeting software requirements ratherthan dealing with the more tedious low-level details of providing a workingsystem.
Before a framework can be deployed it needs to be specialized fora particular use. This can either be done at build time via static dependencies between software modules or at run time via dynamically loadedplug-ins.ICLImage Conversion Library, part of the Symbian OS multimedia subsystem.IPCInter-Process Communication.LDDLogical Device Driver.MixinAn abstract interface that provides a certain functionality to be inherited bya class. The Symbian OS naming convention for these classes is that theystart with an ‘M’.MMUMemory Management Unit.Non-XIPA device which is not XIP-based stores code on disk, usually compressedin some way, and loads it into RAM to be run. This is in addition to theRAM used for the run-time data for each instance. Non-XIP devices basedon Symbian OS are currently the most common type outside Japan.OwnableresourcesResources such as RAM, disk space and communication channels areownable.
Unlike ephemeral resources, you can hold onto them and keepusing them. Such resources can be reserved for your sole use.PDDPhysical Device Driver.Plug-inA software module loaded at run time to add a specific feature or service toa larger software module.PollingThis is where a software object periodically requests information.
This is theopposite of event-driven programming, in which the software object wouldwait to be notified of any changes to the information it is interested in.GLOSSARYxxiWordDefinitionRaceconditionThis is a flaw in a system or process whereby the output or result of theprocess is unexpectedly and critically dependent on the sequence or timingof other events. The term originates with the idea of two signals racing eachother to influence the output first.RAMRandom Access Memory.Real timeThis is a constraint on an operation in which the time between starting andfinishing it must be within a fixed limit.ResourceAny physical or virtual entity of limited availability that needs to be sharedacross the system.SDLThis is the Symbian Developer Library which can be found in every deviceSDK as well as online at developer.symbian.com/main/documentation/sdl .SourcecompatibilityThis is less restrictive than full compatibility as it states only that no sourcecode changes need to be made for a client to work across all versions of thesoftware.Stray signalThis is when a request has been signalled as complete but either there is noactive object available or an active object is found that has neither been setactive nor has a request pending.SWISoftware Installer.TCBTrusted Computing Base can refer to a capability or to the components thatuse the capability, such as the kernel, the file server and, on open devices,the software installer.
These components have unrestricted access to thedevice resources. They are responsible for maintaining the integrity of thedevice and applying the fundamental rules of platform security. The rest ofthe operating system must trust these components to behave correctly andas a result, their code will have been very strictly reviewed.TCEBeyond the TCB, other system components are granted orthogonal restrictedsystem capabilities and constitute the Trusted Computing Environment.This includes servers providing sockets, telephony, certificate management,database access, and windowing services. Each server has just the capabilities it requires; for instance, the windowing server is not granted phonestack access and the communications server is not granted direct access tokeyboard events.TCPTransmission Control Protocol.UDPUser Datagram Protocol.UI vendorA company that provides the user interface layers on top of Symbian OSwhich, along with a base port, is needed to create platforms from whichdevices can be created.
The current UI layers are MOAP, S60 and UIQ.xxiiGLOSSARYWordDefinitionVendorA company or person that provides software for use on a Symbian OSdevice.WSDWritable Static Data is any modifiable globally-scoped variable declaredoutside of a function, or any function-scoped static variables.XIPAn eXecute-In-Place device is one in which code is stored and run directlyfrom disk. This means that the code does not take up any RAM when runalthough each instance still uses RAM for its run-time data, such as itsprogram stack, etc. XIP devices based on Symbian OS are currently the mostcommon type in Japan.1Introduction1.1 About this BookIf you’ve ever asked yourself ‘How do the experts architect software formobile devices?’ then this book is for you.
Common Design Patterns forSymbian OS collects the wisdom and experience of some of Symbian’sfinest software engineers. It distils their knowledge into a set of commondesign patterns that you can use when creating software for Symbiansmartphones.This book helps you negotiate the obstacles often found when workingon a smartphone platform. Knowing the potential problems, and thepatterns used to solve them, will give you a head start in designingand implementing robust and efficient applications and services onSymbian OS.This book is not intended to be a quick start guide to Symbian OS,nor to explain its design or architecture. Other titles from Symbian Pressdo just that, for example [Harrison and Shackman, 2007] and [Morris,2007].
Rather, it aims to capture expert knowledge about programmingpractice specific to Symbian OS and make it available to all developersworking with Symbian OS.We welcome your feedback and contributions and so we have provided a wiki page at developer.symbian.com/design patterns wikipagewhere you can post your experiences with the patterns we describe andshare additional patterns that you know of for Symbian OS.1.2 Who this Book Is ForThis book is suitable for relative beginners as well as experts in SymbianOS development. It will help beginners to make progress quickly whenworking on medium-sized projects. It will also support experts in theirdesign of large-scale and sophisticated software and assist them in learning2INTRODUCTIONfrom the experience of other experts.
The book should help both groups toharness well-proven solutions, as well as specific variations, to individualdesign problems.To get the most out of the book, readers are expected to have someexisting knowledge of Symbian OS and C++, so basic concepts are notexplained in detail. For instance, we assume that you are aware of someof the basic idioms, such as descriptors, and have an understandingof the basic types of Symbian OS classes (e.g.
C, R, T and M classes)and how they behave. The book specifically targets existing SymbianC++ developers whether they’re creating applications or services. Itcan equally well be used by developers internal to Symbian, licenseedevelopers creating devices and third-party developers writing aftermarket applications.If you are new to Symbian OS or want to take a refresher course inthese concepts, there are several books that you could read, including[Harrison and Shackman, 2007] and [Stichbury and Jacobs, 2006], whichdescribe the basics of Symbian C++ development.1.3 Which Version of Symbian OS this Book Is ForThis book applies to Symbian OS v9.1 and onwards, which means that allthe patterns described work in all v9.x releases.
However, a number of thepatterns are not specific to any particular version of Symbian OS and cantherefore be applied to earlier versions of the operating system as well.The patterns contained in this book are also expected to be equallyapplicable to any future version of the Symbian platform.
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