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C/C++ Users Group Library 1996 July
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C-C++ Users Group Library July 1996.iso
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v_09_03
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9n03058a
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1990-12-08
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Listing 6 (lidar_graph.c)
/* ---
lidar_graph task. This program processes
the raw frame buffer. Frame buffers are received
through the graph q, when processing is finished,
the frame buffer is placed on the available queue.
For the sample program, processing and graphing
are replaced by a call to delay which uses
DELAY_TIME cpu time.
--- */
#include <stdio.h>
#include <signal.h>
#include "lidar.h"
#define DELAY_TIME 0.3
main ()
{
int terminate = 0;
int graph_qid, avail_qid;
char *fb_shm;
int alive_sem;
message mptr;
/* --- set process priority --- */
setpriority (PRIO_PROCESS, 0, LIDAR_GRAPH);
/* --- open message queues --- */
graph_qid = msgget (GRAPHICS_Q, 0666 | IPC_CREAT);
avail_qid = msgget (AVAILABLE_Q, 0666 | IPC_CREAT);
/* --- create alive semaphore --- */
alive_sem = sem_get (ALIVE_KEY, 0);
/* -- create shared memory buffers -- */
fb_shm = shmat (shmget (FB_KEY, FRAME_SIZE * N_FRAMES,
0666 | IPC_CREAT), 0, 0);
/* --- tell the world we're open for business --- */
sem_signal (alive_sem);
/* --- while lidar program running --- */
while (!terminate) {
/* --- wait for the next buffer --- */
msgrcv (graph_qid, &mptr, MSG_SIZE, ANYTYPE, NOFLAGS);
/* --- check for termination --- */
if (mptr.key == QUIT)
terminate = 1;
else
delay (DELAY_TIME);
/* --- place buffer on the availaible queue --- */
msgsnd (avail_qid, &mptr, MSG_SIZE, IPC_NOWAIT);
}
/* -- release memory -- */
shmdt (fb_shm);
}
int cpu_hog_func ();
int take_cpu_time = 1;
#define SETTIMER(t,p) \
t.it_value.tv_sec = (int)delta; \
t.it_value.tv_usec = (p - (int)p) * 1000000; \
setitimer (ITIMER_PROF, &t, 0);
/* --- delay and grab cpu time --- */
delay (delta)
double delta;
{
struct itimerval t;
/* --- signal handler for profiler interrupt --- */
signal (SIGPROF, cpu_hog_func);
/* --- turn on timer --- */
SETTIMER(t,delta);
/* --- loop until stop condition --- */
while (take_cpu_time)
/* do nothing */;
/* --- reset loop condition --- */
take_cpu_time++;
/* --- turn off timer --- */
SETTIMER(t,0);
}
cpu_hog_func ()
{
take_cpu_time--;
}