6 Mar
2003
6 Mar
'03
3:20 p.m.
Hello. I need two functions:
make_shm(int size, char *key)
-run by root
-creates a locked shared memory segment
-returns a key (preferably a string) which is used to
access the shared memory
char *request_shm(char *key)
-run by users
-returns the address of the requested shared memory segment
Could somebody please write these routines to me? Or give good
hints? I have Jack and other codes, but it all is confusing
when the shared memory should be accessed from separate process
which is not fork() of the other.
Should I use mmap() or shm_get() approach?
What then is "/dev/shm"? How to use it?
Best regards,
Juhana
6 Mar
6 Mar
3:42 p.m.
On Thu, Mar 06, 2003 at 09:12:03PM +0200, Juhana Sadeharju wrote:
Hello. I need two functions:
make_shm(int size, char *key)
-run by root
-creates a locked shared memory segment
-returns a key (preferably a string) which is used to
access the shared memory
shm segments are identified by key id (key_t), use ftok on a file to turn
a string (the path to the file) into a key.
Could somebody please write these routines to me?
yikes! [ insert nasty comment here ]
Or give good
hints?
_http://www.google.com
_http://www.acm.uiuc.edu/lug/presentations/shm/shm-5.html
_http://www.ecst.csuchico.edu/~beej/guide/ipc/shmem.html
_don't forget to free your shmem, it stays around after the process dies
if you don't pay attention
I have Jack and other codes, but it all is confusing
when the shared memory should be accessed from separate process
which is not fork() of the other.
pass the key id by socket, pipe, (dummy) file, etc. if it's a file you
can just pass the file path/name to the other program and it can use
ftok to generate the key.
rob
----
Robert Melby
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!gt4255a
Internet: async(a)cc.gatech.edu
5:02 p.m.
On Thu, Mar 06, 2003 at 02:33:46PM -0500, rm wrote:
On Thu, Mar 06, 2003 at 09:12:03PM +0200, Juhana
Sadeharju wrote:
Or you can use Posix SHM shm_open(3), which is more portable, in theory.
POSIX shm segments are identified by a string.
- Steve
Hello. I need two functions:
make_shm(int size, char *key)
-run by root
-creates a locked shared memory segment
-returns a key (preferably a string) which is used to
access the shared memory
shm segments are identified by key id (key_t), use ftok on a file to turn
a string (the path to the file) into a key. 
3:42 p.m.
On Thu, 6 Mar 2003, Juhana Sadeharju wrote:
Hello. I need two functions:
make_shm(int size, char *key)
-run by root
-creates a locked shared memory segment
-returns a key (preferably a string) which is used to
access the shared memory
char *request_shm(char *key)
-run by users
-returns the address of the requested shared memory segment
Could somebody please write these routines to me? Or give good
hints? I have Jack and other codes, but it all is confusing
when the shared memory should be accessed from separate process
which is not fork() of the other.
The sharedmem handlers in the aipc package, (which I'm sort of
working on), is extremely easy to use.
Just define a common filename_prefix for all your processes,
and let them call the function:
struct aipc_sharedmem *aipc_sharedmem_new(
char *filenames_prefix,
int size,
int timeout
)
The first process to call this function with the same
filenames_prefix argument, and a size larger than 0,
will allocate the memory. If size is 0, the function
will wait for 'timeout' usecs and either give up and
return NULL, or return shared memory.
This might not be exactly what you're looking for, but at
least it'll give you a start.
You can find aipc at http://www.notam02.no/arkiv/src/k_jack.tar.gz/aipc/
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3 comments
4 participants
participants (4)
-
Juhana Sadeharju -
Kjetil S. Matheussen -
rm -
Steve Harris