Re: [png-mng-implement] PNG library in a multi-thread environment

[Andreas D. <ad...@di...>]

On Jun 23, 2014, at 6:35 AM, Dr. Yehuda Singer <yeh...@ll...> wrote: 
> Dear Andreas
>  
> We use the PNG library on an x86-64 Red Hat machine.  A serial program reads from an input file, processes the information and writes to a different file.
> Now, we want to program in a multi-thread environment using pthreads library. One thread reads the input file, while the other thread processes the information and writes it to another file.
> Given a series of input file: f1,f2, f3….
> While contents of file1 are processed by one thread, the other thread reads file2. That means the PNG library has to be re-entrant.  However, the libraries installed on our machine does our requirement.
> The linker uses the shared object located at /usr/lib64.
> Can you help us?

If you are contacting me it probably means you have a very old version of libpng, since I have not been the maintainer for many years.

That said, it surprises me that libpng is not re-entrant, since each encoding and decoding stream should have its own state.  I couldn't really say more without knowing more details about how you are using it.

I would suggest to contact the PNG development list at:
http://lists.sourceforge.net/lists/listinfo/png-mng-implement

I've CC'd that list, but I'm not sure if I can post since I am no longer subscribed there.

Cheers, Andreas

PS - if this does make it through to the list - hi to everyone :-)