I wanted to know whether is it possible to make use of COM component in other platforms like linux,etc..,
My question is that COM component is supposed to be registered with OS &
For that OS need something like registry so that client can use COM components.
Can anyone shed light on my question ?
If you want to have the ability to create COM classes by specifying a "string", and wish the OS can search for the correct binary library to load from as well as creating the actual COM class (object), then some form of registering is needed.
Other than that, if you only want to use COM-style interfaces (interfaces derived from IUnknown, IDispatch, etc) you can do that in any C++ languages (as long as the vtable implementation of that C++ compiler is compatible with COM).
Finally, some COM capabilities such as inter-process communication and remote invocation are provided as part of Windows OS. You will need to implement your own if these capabilities are needed.
The Wikipedia page on CORBA appears to have some references to a number of choices. Check the See Also section.
The wikipedia entry for Microsoft COM says in the "Overview" that "the interface standard has been implemented on several platforms", but fails to specify which ones. If you're looking for a cross-platform approach, you may be better off with something like XPCOM instead.
Technically speaking, COM is just an architecture that can be implemented in any platform. Looking up registered classes in the registry, for example, is something you could implement in an equivalent way on any other platform. The rest of it is about DLLs and MIDL, which you can get working on any platform.
Practically speaking, COM is for Windows (and even that's dying pretty quickly).
The theoretical answer is yes, it's possible to use COM components on other platforms.
Here's an article from way back in 1998 on Building COM Components on UNIX. However, even back in the day this was not a popular (or prudent!) approach.
Related
I have an application which I need to port on Linux. I was thinking to use Free Pascal the problem is the application uses Windows API's to perform tasks such as serial port communication etc... Is there a msdn for linux users or a book covering how linux works internaly if there are apis.
I am very confused.
Well, it's sad to say but if your code in very Windows-dependend (not VCL depended!) then probably it'll be faster to write the application from the begining rather then porting it.
But if it's only serial port matter then give a try to multiplatform SynaSer library, find it here: http://synapse.ararat.cz.
hope this help :)
Robert Love has a book on Linux Systems Programming - that will cover this area and Love's books are generally good, so it is worth looking at.
It's not entirely clear from your question, but if your concern is that there are specific calls to hardware controlling functions in your Windows application that make it difficult to port I would suggest that is a misplaced fear. Both Windows and Linux operate on the principle that the application level programmer should be kept away from the hardware and that all that should be handled by the operating system kernel and only be accessible to applications via system calls. As the kernels of different operating systems face similar demands from users/applications, they tend to have system calls that do the same sorts of things. It is necessary to match the system calls to one another but I can see no reason why that should be impossible.
What may be more troublesome is that your Windows application may rely heavily on the Windows executive's windowing code/API. Again finding analogues for your code is not impossible but is likely to be a bit more complex e.g. in Linux this stuff is generally not handled in the kernel at all (unlike Windows).
But then again, your code may be written against a portable toolkit/library like Qt which would make things a lot easier.
Good luck in any case.
If the program contains GUI code you must use linux libraries like GTK/XLIB in order to create windows, forms, buttons, etc...
Windows specific functions (like EnterCriticalSection, WaitForSingleObject or _beginthreadex) must be replaced with equivalent linux api functions (a nice tutorial can be found here:
"www.ibm.com/developerworks/systems/library/es-MigratingWin32toLinux.html") or you can use libraries such as w2lpl or wine
A useful library for this kind of problems i've found at http://www.adontec.com/windows-to-linux-port-library.htm
I've had great experiences just using WINE. (https://www.winehq.org/)
You don't really port your app at all. You just make sure it doesnt violate some of the basc constraints of WINE and just run it as is. WINE (though is says it is not) is an emulator of the windows API's and will just do the translation for you. It's pretty complete in its coverage of the API's.
I want to develop a simple windows manager, but do not know which library to use. Requirements:
Take advantage of the existing high-level libraries to deal with fonts, images. Like GTK+, Clutter, GDK. But keep the design-relevance things out, which libraries should I use? Because I tried to use XCB, which is really painful. And I've heard about Wayland, and if I write it in XCB, it wouldn't be portable to Wayland.
I've read some posts on WM development, typically use XCB and Xlib, I think they are too low-level and I don't want to repeat others work. I want a more user-friendly WM, but keep simple and flexible.
The biggest issue is not the library to use. It is the complexity of the requirements, as dictated by ICCCM and EWMH.
A standard compliant window manager is quite complex, because the standards defining it are complex, and because the X11 protocol is complex.
You might fork an existing WM instead.
But any library capable of X11 protocol exchange can fit the bill.
and I am not sure that Wayland has window managers
I'd split the project in a (low-level) window manager on top of the core X11 libraries, and a high-level part implementing the UI to control the window manager, utilizing whatever toolkit you feel comfortable with.
The difficulty in using a toolkit is that these are not designed to be used from inside a window manager, i.e. the toolkit might expect to be able to send a message to the window manager and receive a reply without returning to "user" code in the middle.
Plus, this allows some more flexibility when using the window manager from different environments -- desktop integrators may choose to rewrite some of the control UI to better match the rest of the system, leaving the core service unaffected.
You can't use a high-level GUI toolkit to develop a window manager. These GUI toolkits are independent of the window manager and don't have any way to communicate directly with it - only in the ways defined by the standards.
I'm moving from windows programming (By windows programming I mean using Windows API) to Linux Programming.
For programming Windows, the option we have is Win32API (MFC is just a C++ wrapper for the same).
I want to know if there is something like Linux API (equivalent to WINAPI) that is exposed directly to the programmer? Where can I find the reference?
With my little knowledge of POSIX library I see that it wraps around part of Linux API. But what about creating GUI applications? POSIX doesn't offer that. I know there are tons of 3rd party Widget toolkits like gtk, Qt etc. But I don't want to use the libraries that encapsulates Linux API. I want to learn using the "Core Linux API".
If there are somethings that I should know, please inform. Any programmer who is familiar with both Windows & Linux programming, please map the terminologies of Linux world so that I can quickly move on.
Any resources (books,tutorials,references) are highly appreciated.
I think you're looking for something that doesn't exactly exist. Unlike the Win32 API, there is no "Linux API" for doing GUI applications. The closest you can get is the X protocol itself, which is a pretty low level way of doing GUI (it's much more detailed and archaic than Win32 GDI, for example). This is why there exist wrappers such as GTK and Qt that hide the details of the X protocol.
The X protocol is available to C programs using XLib.
What you must understand is that Linux is very bare as to what is contained within it. The "Core" Linux API is POSIX and glibc. Linux is NOT graphical by default, so there is no core graphics library. Really, Windows could be stripped down to not have graphics also and thus not have parts of the win32 API like GDI. This you must understand. Linux is very lightweight compared to Windows.
For Linux there are two main graphical toolkits, GTK and Qt. I myself prefer GTK, but I'd research both. Also note that GTK and Qt exist for Windows to, because they are just wrappers. If you go take a look at the X protocol code for say xterm, you'll see why no one tries to actually creating graphical applications on top of it.
Oh, also SDL is pretty nice, it is pretty bare, but it is nice if your just needing a framebuffer for a window. It is portable between Linux and Windows and very easy to learn. But it will only stretch so far..
Linux and win aren't quite as different as it looks.
On both systems there exists a kernel that is not graphical.
It's just that Microsoft doesn't document this kernel and publishes an API that references various different components.
On Unix, it's more transparent. There really is a (non-GUI) kernel API and it is published. Then, there are services that run on top of this, optionally, and their interfaces are published without an attempt to merge them into an imaginary layer that doesn't really exist.
So, the lowest GUI level is a the X Window System and it has a lowest level library called Xlib. There are various libraries that run on top of this one, as you have noted.
I would highly recommended looking at the QT/C++ UI framework, it's arguably the most comprehensive UI toolkit for any platform.
We're using it at work developing cross platform apps that run on windows, osx and linux.
It also runs on Nokia's smart phone Operating System Maemo which has recently been merged with Intel's Moblin Linux OS, now called MeeGo.
This is going to sound insane since you're asking about "serious" stuff like C++ and C (and the "core linux API"), but you might want to consider building in something else. For instance:
Java Swing (many people love it! Others hate it and call it obsolete)
Mono GTK# (C# or VisualBasic or whatever you want, lots of people say it's pretty cool, but they're not not that many people)
Adobe AIR (ActionScript, you might hate it)
Titanium (totally new and unproven, but getting a lot of buzz in the iPhone world, at least)
And many other possibilities, some of which let you work on multiple platforms at once.
Sorry if this answer is not at all what you're looking for. The "real" answers on Linux are "pick a toolkit," which is also no answer at all :)
Have a look at Cairo. This something roughly similar to GDI+ and is under the hood of some of of the few usable GUI programs for Linux i.e. Firefox or Eclipse (SWT). It wraps most the natsy and ancient Linux stuff for you into a nice API that runs on most Linux installations without locking you into a entire subsystems like GTK or QT.
There is also the docs for the two different desktop platforms: Gnome and KDE that might help you down that road.
Is it possible to write a mobile application with J2ME and whenever we want to implement a functionality not offered by J2ME call native mobile API ? (kind of like what is done with .NET, whenever you need something not provided, you just call the Win32 API from the .NET platform).
While JNI is not officially supported in J2ME, the Symbian implementation of J2ME obviously uses something very similar.
Since most J2ME APIs have a corresponding Symbian OS C++ API, what Symbian did (a lot) is develop adaptation layers between the 2.
Between that and the new modular architecture of the IBM J9 virtual machine (from Series60 3rd edition feature pack 2 onward), it is technically possible to add a new API to the virtual machine without actually needing to recompile most of a handset firmware.
However, third party developers simply are not allowed to do it without a lot of help from the handset manufacturer.
A loopback socket connection is the solution that people have tipically implemented to transfer data accross the language barrier. Large-scale deployment is not the easiest task, though, as you technically need to install 2 applications on the device. Once you understand the threading model of the Symbian J2ME implementation, you also realize how ugly and inefficient a hack it is.
When you reach that kind of issue, it's time to learn Symbian OS C++ and do it right.
No. That's not possible with Java ME.
Only sort of. Actually it is possible but not directly. You can write a native server that listens on a local socket and send requests to it from your Java MIDlet. Someone even released a framework to do this called MIDP-JNI (as opposed to real JNI). Obviously the form of the solution imposes some limitations on what you can do with it but it isn't actually impossible.
Be aware that using this approach can make your application much more complex to debug.
If you are specifically looking out for Nokia/Symbian, then APIBridge http://wiki.forum.nokia.com/index.php/J2ME_API_Bridge_Interface could be a solution. Typically it is the 'official' version of 'native server on local socket' kind of thing. The APIBridge is 'extensible' & you can write your own 'plugins' for your suitable 'low-level' task.
I am planning to use SCTP for a embedded Linux project. Anybody has some comments on SCTP usage, mostly in one-to-many mode? Did it beat using a home-made UDP-based equivalent solution?
I control the network environement and all devices involved, so compatibility is not an issue.
I have made extensive use of lksctp and have found it to be robust and interoperable with many other implementations of sctp. The standard for the sockets API for SCTP is still evolving but is quite mature and I would expect any further changes to be backwards compatible.
I would use it with confidence.
The ACE library has a performance test for SCTP, so I would assume that it works.
Currently these programs provide the only example code on
how to use ACE's wrapper-facades for SCTP. In the future additional
code will be placed in the ACE_wrappers/examples/IPC_SAP/SOCK_SAP
directory.
Using a framework like ACE is a good idea anyway, as it alloes you to program on a higher level and shields you from the error prone low level details of socket programming. As an additional bonus your code will be portable to all platforms that ACE supports.
Best answer is the comment:
Also, SCTP support in Glibc is less than ideal (in other words, non-present) -- you must use the libraries from lksctp, and it's not entirely well-integrated into the normal sockets API. Just one more reason to use a nice library that encapsulates the low-level functionality :) – ephemient