memory sharing - not shared memory -


 
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# 1  
Old 04-23-2007
Network memory sharing - not shared memory -

hi,

this is the problem: i want to swap a linked list between 4 processes (unrelated), is there any way i can do that just by sending a pointer to a structure?
Code:
//example
typedef struct node
{
   int x;
   char c;
   struct node *next;
} node;

or i should send the items ( x,c ) by value and reconstruct the list ?
my solution: create the list in a shared location in memory, where all the processes can use the same reference to manipulate or read the list, but if i use malloc(); i can't control the physical place where the memory is allocated (that's what i know) Smilie

any help guys is appreciated, thanks
# 2  
Old 04-30-2007
hi elzalem,
there is no such think like a memory location since mem may be swaped out or what ever.
The solution depends on your requierements.
You can use a file in shared mem, the most simple solution.
of if not possible use a 'server task' that handles requests into the data structure
# 3  
Old 04-30-2007
Smilie thanks for your reply grumpf , I've wrote a header file that contains several function to handle data structure swapping, i used message passing (message queues) but the thing is that i had to send everything by value (my data structures are complex :each node contains a queue and are filled with pointers).

I was hoping to be able to find a solution similar to the threads where all the processes share all the variables...
# 4  
Old 04-30-2007
Quote:
Originally Posted by elzalem
I was hoping to be able to find a solution similar to the threads where all the processes share all the variables...
There is, it's called shared memory, but for some reason you discounted this option in your title.

Look at mmap(MAP_SHARED|MAP_FIXED)
# 5  
Old 05-01-2007
i have 2 linked lists that are constantly growing or shrinking, both r visible to all processes, i don't want each process to have a copy, i hope you're understanding what i mean.
without "shared memory" is it possible?
# 6  
Old 05-01-2007
Quote:
Originally Posted by elzalem
i have 2 linked lists that are constantly growing or shrinking, both r visible to all processes, i don't want each process to have a copy, i hope you're understanding what i mean.
without "shared memory" is it possible?
... and the moon on a stick presumably?

You can share it in memory or have another server process that contains the list and all other processes use some form of IPC or RPC to access.

You can't share something by not sharing it.

Last edited by porter; 05-01-2007 at 08:26 PM..
# 7  
Old 05-02-2007
Quote:
Originally Posted by porter
...have another server process that contains the list and all other processes use some form of IPC or RPC to access...
in the end that's what i did! But i was trying to see if there is something i don't know about in unix that can allow me to:

p1 and p2 are 2 processes,

in p1:
int *var=malloc(sizeof(int));
send var to p2 (the address not the value)

in p2:
*var = 4; // normaly that'll give an error

I need to allow p2 to gain access to all the memory space of p1. i can simply put em in a shared memory, but i was trying to find a substitute!
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