1 | #include "semaforo.h"
|
---|
2 |
|
---|
3 | /* Declare some local functions. */
|
---|
4 | FORWARD _PROTOTYPE(void init_server, (void) );
|
---|
5 | FORWARD _PROTOTYPE(void get_work, (message *m_ptr) );
|
---|
6 | FORWARD _PROTOTYPE(int do_up, (message *m_ptr) );
|
---|
7 | FORWARD _PROTOTYPE(int do_down, (message *m_ptr) );
|
---|
8 |
|
---|
9 | /* semaforo globale al server */
|
---|
10 | semaforo sema;
|
---|
11 |
|
---|
12 | /*===========================================================================*
|
---|
13 | * main *
|
---|
14 | *===========================================================================*/
|
---|
15 | PUBLIC int main(void){
|
---|
16 | message m;
|
---|
17 | int result;
|
---|
18 | /* Initialize the semaphore server. */
|
---|
19 | init_server();
|
---|
20 | /* Main loop of server. Get work and process it. */
|
---|
21 | while(TRUE) {
|
---|
22 | /* Block and wait until a request message arrives. */
|
---|
23 | get_work(&m);
|
---|
24 | /* Caller is now blocked. Dispatch based on message type. */
|
---|
25 | switch(m.m_type) {
|
---|
26 | case SS_UP: result = do_up(&m); break;
|
---|
27 | case SS_DOWN: result = do_down(&m); break;
|
---|
28 | default: result = EINVAL;
|
---|
29 | }
|
---|
30 | /* Send the reply, unless the caller must be blocked. */
|
---|
31 | if (result != EDONTREPLY) {
|
---|
32 | m.m_type = result;
|
---|
33 | send(m.m_source, &m);
|
---|
34 | }
|
---|
35 | }
|
---|
36 | return(OK);
|
---|
37 | }
|
---|
38 |
|
---|
39 | /*===========================================================================*
|
---|
40 | * init_server *
|
---|
41 | *===========================================================================*/
|
---|
42 | PRIVATE void init_server(void){
|
---|
43 | sema.s = 0;
|
---|
44 | sema.quanti = 0;
|
---|
45 | }
|
---|
46 |
|
---|
47 |
|
---|
48 | /*===========================================================================*
|
---|
49 | * get_work *
|
---|
50 | *===========================================================================*/
|
---|
51 | PRIVATE void get_work(message *m_ptr){
|
---|
52 | int status = 0;
|
---|
53 | status = receive(ANY, m_ptr); /* this blocks until message arrives */
|
---|
54 | if (OK != status)
|
---|
55 | panic("SS","failed to receive message!", status);
|
---|
56 | }
|
---|
57 |
|
---|
58 | PRIVATE int do_down(message *m_ptr){
|
---|
59 | if (sema.s > 0){
|
---|
60 | sema.s -= 1;
|
---|
61 | return(OK);
|
---|
62 | }
|
---|
63 | if (accoda(&sema, m_ptr->m_source) < 0) return(EFAULT);
|
---|
64 | printf("Accodato %d (semaforo %d [%d])\n",
|
---|
65 | m_ptr->m_source, sema.s, sema.quanti);
|
---|
66 | return(EDONTREPLY); /* non risponde: il chiamante rimane bloccato */
|
---|
67 | }
|
---|
68 |
|
---|
69 | PRIVATE int do_up(message *m_ptr){
|
---|
70 | sema.s += 1;
|
---|
71 | if (sema.quanti > 0){
|
---|
72 | int waiting = scoda(&sema);
|
---|
73 | if (waiting < 0) return(EFAULT);
|
---|
74 | sema.s -= 1;
|
---|
75 | printf("Scodato %d (semaforo %d [%d])\n",
|
---|
76 | waiting, sema.s, sema.quanti);
|
---|
77 | m_ptr->m_type = OK;
|
---|
78 | send(waiting, m_ptr);
|
---|
79 | }
|
---|
80 | return(OK);
|
---|
81 | }
|
---|