symbian programming overview. 6.893 spring 2004: symbian larry rudolph how to program cellphone?...
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Symbian Programming
Overview
6.893 Spring 2004: Symbian Larry Rudolph
How to program Cellphone?
Limited to Series 60 phones
Java MidP 2.0 (see wiki, forums)
compile offline and load
limited API
C++
full API
non-standard C++
Python -- coming soon
6.893 Spring 2004: Symbian Larry Rudolph
Getting App onto Phone
Compile application into .app
Create package file (.pkg)
resources files, libraries
including a digitally signed certificate -- authentication -- and author’s key (.cer and .key)
Installation file (.sis) via makesis tool
Transfer to phone via email or bluetooth and then user installs
6.893 Spring 2004: Symbian Larry Rudolph
Overview of SymbianSymbian is a company that produces an operating system
Originally developed for handheld Psion and called Epoc Operating System
Symbian is 40% owned by Nokia, partly owned by Sony Ericson, partly owned by Psion, and others
Require 70% agreement to make basic changes
6.893 Spring 2004: Symbian Larry Rudolph
A little history
Started in early days of C++
Goal to be
real-time
small footprint
small touch-screen
integrated
secure & reliable
6.893 Spring 2004: Symbian Larry Rudolph
Biggest Security Flaws
Applications must be certifiedIf not certified, user choice to continueApplications either GUI or Server
a server app can easily hideFile system not fully exposed to userFile system has no access control lists
despite kernel/user execution, any application can do anything
Application can control all keys
6.893 Spring 2004: Symbian Larry Rudolph
Biggest Programming Issue
System may run for years
Persistent state across power downs
addressbook application may never terminate
Small memory leaks accumulate over time
Must write perfect leak-free code!
unachievable goal
try anyway
6.893 Spring 2004: Symbian Larry Rudolph
Why will there be Memory Leaks
No garbage collection
No memory protection
no page tables
No “try”, “throw”, “catch”
operating systems calls
trap harness and leave
Silly naming conventions
6.893 Spring 2004: Symbian Larry Rudolph
Keep track of all allocated objects
Always keep live pointer to anything allocated in heap
can use pointer to deallocate
extra care when constructing compound classes
Deallocate after use
6.893 Spring 2004: Symbian Larry Rudolph
Stacks
Objects allocated at top of stack
Top of stack disappears when procedure returns
Cannot construct objects on stack since they maybe constructed in procedure
Objects go in heap
No reference counts on objects
6.893 Spring 2004: Symbian Larry Rudolph
Heap allocation
Within one procedure:
Allocate pointer to heap object
Allocate (construct) object on heap
Use object
Deallocate object on heap
Deallocate pointer to heap object
6.893 Spring 2004: Symbian Larry Rudolph
Pointer to object not on stack
If pointer is on stack, what happens when there is an exception?
may pop out several levels of stack
Need to put objects on different type of stack
one that does not disappear during exception
keep pointers in heap on “cleanup stack”
6.893 Spring 2004: Symbian Larry Rudolph
Cleanup Stack
Cleanup Stack resides in heap
what if Construct causes exception?
Class* self = new(ELeave) Class(aInt)CleanupStack::PushL(self)self->Construct(aObj);CleanupStack::Pop(self);
6.893 Spring 2004: Symbian Larry Rudolph
Exception Handling
On exception, cleanup stack is popped and objects are removed.
(always check for null pointers)
Exceptions may be handled far back in time of program execution
6.893 Spring 2004: Symbian Larry Rudolph
In the days before “try”
TRAPD(error, callExampleL() );
void CreateObject() {Object* obj = new (ELeave) Object
Trapd is a trap harness
It calls proceedure callExample()
Normal return, TRAPD continues
Exception, has error set to code
6.893 Spring 2004: Symbian Larry Rudolph
Throwing exceptions
User::Leave()
of allocation runs out of memory in a
new(ELeave)
6.893 Spring 2004: Symbian Larry Rudolph
Descriptors
TBuf
TBufC
HBufC
TPtr
TPtrC
6.893 Spring 2004: Symbian Larry Rudolph
Active Scheduler
Non-preemptive scheduler
Create a scheduler
Post wait for event(s)
Return to scheduler
Handle event
6.893 Spring 2004: Symbian Larry Rudolph
6.893 Spring 2004: Symbian Larry Rudolph
O2S How it helps you
Overcome firewalls
Overcome IP address, Dynamic DNS
do not have to program in the names of all services & devices
Publish and subscribe facility
HUB is useful resource
Python based
UI independence
6.893 Spring 2004: Symbian Larry Rudolph
O2S Planner
Better support for publish-subscribe
Easier to piece together application
Better Human support
6.893 Spring 2004: Symbian Larry Rudolph
More on O2S
Branch in O2S CVS directory
easier to ask for help
Name stuff based on group name
can easily find each other
6.893 Spring 2004: Symbian Larry Rudolph
Eye-toy
Playstation 2 game
Camera watches user
Identify body outline, especially hands and head
Hands punch virtual characters
Head hits balloon or soccer ball
6.893 Spring 2004: Symbian Larry Rudolph
Mosquito