How does NaCl work in following scenario

Question

I have a NPAPI plugin that is used for Screen-sharing.

For that I am using zlib, jpeg, tight-vnc libraries along with a library(say libX) that is developed by me.

Now I wish to port it to NaCl.

libX has structure like:

                     /X/commonfiles

                     /X/win/*.cpp *.h

                     /X/linux/*.cpp *.h

                     /X/mac/*.cpp *.h *.mm

These directories contain cpp files specific to the platform.

I make use of makefiles to compile them according to the platform.

But I am unable to understand how NaCl toolchain will generate a nexe or pexe from my library/code.

Is there any makefile we have to consider or any other thing I'm missing.

Please Help!

Thanks!!!

How are you currently building libX for Linux? It probably will be easiest if you use the same build system, but modify your compiler to use the NaCl tools (GCC,AR,LD,etc.) instead. We do this in the naclports library (code.google.com/p/naclports), and it usually requires very few modifications. — binji
I have already mentioned that I use Makefiles. But what about windows code or mac code? As per my understanding I should be getting a single nexe/pexe file that serves my purpose(live Screen-Sharing) on all OSes[as this exe would run under Chrome sandbox]. — rohitvk
So my question is that is NaCl able to generate generic code out of platform specific code that is part of my libX. To avoid using #ifdef (platform specific instructions] in my code, I've put my code files under directories like win/ mac/ as mentioned above. Now I want to understand what I've to do in order to compile my libX with NaCl to produce pexe without making fundamental chages. Hope my query is clear! thanks for the response. — rohitvk

binji binji · Accepted Answer · 2013-11-14T22:49:05

First, NaCl is a sandboxing technology that provides security when running native code in a browser. As such, you will not be able to access the user's filesystem directly (as you would be able to with an NPAPI plugin). You may need to modify your library to support NaCl as a new "operating system".

That said, a lot of functionality is available through the Pepper Plugin API (PPAPI), which allows your NaCl plugin to communicate with the browser. In addition, the nacl_io library that comes with the NaCl SDK provides a more familiar POSIX-like interface, to support File I/O and sockets.

It shouldn't be too hard to try building your library using the pnacl toolchain as follows:

Download the Native Client SDK. When you're done, you should have a directory called pepper_31 that contains the Native Client SDK.
The Native Client build will likely be most similar to your Linux port. In your makefile, change any build rule that executes your native toolchain to use the pnacl toolchain instead, e.g.
- g++ => pepper_31/toolchain/linux_pnacl/bin/pnacl-clang++
- ar => pepper_31/toolchain/linux_pnacl/bin/pnacl-ar
- etc.
Try building your Linux build. You probably will have some compilation failures, maybe from missing libraries, maybe from header differences. Depending on what your library does, you may need to modify it to use the PPAPI, to access things like graphics, sockets, URL requests, File IO, etc.

Once you do this, you'll likely have some more specific questions about how to implement features that you need. :)

How does NaCl work in following scenario

1 Answers