shared - i need it to be useful

[Neia Neutuladh]

On Sat, 20 Oct 2018 22:47:14 -0700, Manu wrote:
> Looking at the meat of the program; you open a file, and distribute it
> to do accesses (I presume?)....
> Naturally, this is a really weird thing to do, because even if the API
> is threadsafe such that it doesn't crash and reads/writes are
> serialised, the sequencing of reads/writes will be random, so I don't
> believe any sane person (let alone an expert) would write this
> program... but moving on.
> Then you wait for them to finish, and close the file.
> 
> Fine. You have a file with randomly interleaved data... for whatever
> reason.

I'd expect almost every nontrivial multithreaded program to do this. It's 
called a log file.

You don't need to read data pointed at by a log file, but you do need to 
read the FILE* or the file descriptor.

Database-like things using a journal file might need a shared file for 
both reading and writing.

> So, you call closeFile immediately and read/write start returning null.

You start threads. You give them access to the log file. You wait for the 
threads to exit. Then you close the file.