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a short example:
#include <semaphore.h> // for semaphore opperations
// global buffer, used to store incoming messages.
// the buffer is checked by the application waiting for the message.
struct inn_msg{
char *msg;
sem_t lock;
};
//create a semaphora struct
struct inn_msg *message;
// initiate the semaphora->lock to 0 (zero)
sem_init(&message->lock,NULL,0);
// process 1
int process_1{){
//whenever i copy something to message->msg i must update the
message->msg = some memory _location;
// update the semaphora
sem_post(&message->lock);
}
//process 2
int process_2(){
//wait for something to happend
ret = sem_wait(&message->lock);
//do something with message->msg
}
after included the semahopra.h, creating a semaphora
and initializing it, the idea here is that sem_post will increase
message->lock by 1. the process doing the sem_wait will wait for
message->lock to be nonzero before it starts executing further.
this is how access to shared memory can be handled.
hope this helps, if not, lemme know :)
kenneth
Samuel Winchenbach wrote:
> Does anyone have any code that implements semaphores and shows where they
> might be useful? That is one place that the documentation seems a little
> weak. Thanks,
>
> Sam
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Message has 1 Reply:
 | | Re: semaphores
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| Would it be possible for you to send the entire source? I would like to see how it interacts with the rest of the program. Thanks for your help. "kenneth johansen" <kennethj@stud.cs.uit.no> wrote in message news:3CDAC372.34D72C....uit.no... (...) (...) (23 years ago, 10-May-02, to lugnet.robotics.rcx.legos)
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Message is in Reply To:
| | semaphores
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| Does anyone have any code that implements semaphores and shows where they might be useful? That is one place that the documentation seems a little weak. Thanks, Sam (23 years ago, 9-May-02, to lugnet.robotics.rcx.legos)
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