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Old 01-16-2006, 01:00 PM   #1
level3
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Registered: Jan 2006
Posts: 13

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> File Mapping And Pthreads, How to map file in memory?


Hello

I am trying to map a file in memory to use with pthreads (read/write blocks), but when I try to use a easy funcion to get void pointer, returned pointer is diferent each time.

The first place, the programs calls mmap with MAP_SHARED,

if ((source = mmap (0, fst1.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, file, 0)) == (void *) -1)
{
perror ("Error ");
return (fail);
}

Why return different pointer each time?

Another method to easy manage of maped files like AIX file_ptr=shmat (fd, 0, SHM_MAP); ?


Thanks in advance.
 
Old 01-16-2006, 10:13 PM   #2
foo_bar_foo
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Registered: Jun 2004
Posts: 2,553

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you have put the argument 0 or NULL as the first argument to mmap which is a way of saying just choose any available start address.
 
  


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