Reading dynamically growing file using NSInputStream

Question

I should use Objective-C to read some slowly growing file (under Mac OS X).

"Slowly" means that I read to EOF before it grows bigger.

In means of POSIX code in plain syncronous CI can do it as following:

while(1)
{
    res = select(fd+1,&fdset,NULL,&fdset,some_timeout);
    if(res > 0)
    {
        len = read(fd,buf,sizeof(buf));
        if (len>0)
        {
            printf("Could read %u bytes. Continue.\n", len);
        }
        else
        {
            sleep(some_timeout_in_sec);
        }
    }
}

Now I want to re-write this in some asynchronous manner, using NSInputSource or some other async Objective-C technique.

The problem with NSInputSource: If I use scheduleInRunLoop: method then once I get NSStreamEventEndEncountered event, I stop receiving any events.

Can I still use NSInputSource or should I pass to using NSFileHandle somehow or what would you recommend ?

Answer 1

I see a few problems.

1) some_Timeout, for select() needs to be a struct timeval *.

2) for sleep() some_timeout needs to be an integer number of seconds.

3) the value in some_timeout is decremented via select() (which is why the last parameter is a pointer to the struct timeval*. And that struct needs to be re-initialized before each call to select().

4) the parameters to select() are highest fd of interest+1, then three separate struct fd_set * objects. The first is for input files, the second is for output files, the third is for exceptions, however, the posted code is using the same struct fd_set for both the inputs and the exceptions, This probably will not be what is needed.

When the above problems are corrected, the code should work.