/* rmc.c */

/* Resource manager client */

#include <stdio.h>
#include <mqueue.h>
#include <errno.h>

#define MAX_RES 16

#define CODE_READ  11
#define CODE_WRITE 12
#define CODE_FREE  13

#define CLIENT_BOX "/rm.client1"

struct rrtype
{
   char reply_to[12];         /* Name of reply msg queue         */
   int  client_id;            /* Logical id of the client proc.  */
   int  request_id;           /* For matching reqs w/ replies.   */
   int  resource_id;          /* Value 0 - MAX_RES -1            */
   int  action;               /* 11 = Rd  | 12 = Wrt | 13 = Free */
};

/* Skeleton of a request message  */

struct rrtype mskel =
{
   CLIENT_BOX,
   1,
   0,
   0,
   0
};

/* Reply box attributes */

struct mq_attr mqattr =
{
   0,
   40,
   sizeof(struct rrtype),
   0
};

/* Print a message */

void printbuf(
struct rrtype *rr)
{
   printf("\n %-12s %4d %4d %4d %4d \n",
           rr->reply_to,
           rr->client_id,
           rr->request_id,
           rr->resource_id,
           rr->action);
}

void main(
int  argc,
char **argv)
{
   mqd_t mqs;
   mqd_t mqr;
   int   i;

   struct rrtype sbuf;
   struct rrtype rbuf;

   mqs = mq_open("/rm.server", O_WRONLY, 0700, NULL);
   mqr = mq_open(CLIENT_BOX, O_CREAT | O_RDONLY, 0700, &mqattr);

/* Send bunch of read requests */

   for (i = 0; i < 32; i++)
   {
      memcpy(&sbuf, &mskel, sizeof(struct rrtype));
      sbuf.request_id  = i + 1;
      sbuf.resource_id = i % MAX_RES;
      sbuf.action      = CODE_READ;
      mq_send(mqs, (char *)&sbuf, sizeof(sbuf), NULL);
   }

/* Get back the permissions... and release resources */

   for (i = 0; i < 32; i++)
   {
      mq_receive(mqr, (char *)&rbuf, sizeof(rbuf), NULL);
      printbuf(&rbuf);
      rbuf.action = CODE_FREE;
      mq_send(mqs, (char *)&rbuf, sizeof(rbuf), NULL);
   }

/* Send and receive some write requests */

   for (i = 0; i < 32; i++)
   {
      memcpy(&sbuf, &mskel, sizeof(struct rrtype));
      sbuf.request_id  = i + 1;
      sbuf.resource_id = i % MAX_RES;
      sbuf.action      = CODE_WRITE;

      mq_send(mqs, (char *)&sbuf, sizeof(sbuf), NULL);
      mq_receive(mqr, (char *)&rbuf, sizeof(rbuf), NULL);
      printbuf(&rbuf);
      rbuf.action = CODE_FREE;
      mq_send(mqs, (char *)&rbuf, sizeof(rbuf), NULL);
   }

   mq_unlink(CLIENT_BOX);
}

/* Yes, it is the case that request id's are being "recycled" */