Implement Functionality Currently Missing in dup

[Joel Sherrill]

Wei Shen wrote:
> Hi,
>  
> I would like to add dup to my GSoC proposal on posix fifo/pipe, for 
> both of them are related to file system, which is a topic I am 
> familiar with. The open project page does not give a clear description 
> about the task. From the source code, I think what is missing is not 
> in the dup implementation, but the open file descriptor array. Maybe, 
> it should store the pointers to actual file descriptors but not the 
> descriptor itself. And, is there need to support dymamic expansion of 
> the fd array?
>  
Look at the psxfile01 test.  I think that's the one that has some specific
test cases which do not work.  It could be IMFS specific or in the ioctl.
My recollection is that there no attempt to "dupe" the file state.

I do not think it is the case that extending the file descriptor array 
would help.
A user application configures the number of file descriptors that they 
want in
an application and there should be plenty.  This is simply missing 
functionality.

You might also want to look at Asynchronous IO and List IO functions.  They
are in the same area and should be interesting.  Probably not much more than
having a server task interact with the requests those functions make.
> Regards,
> Wei Shen


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