From fed8339de92f60c271fb37e9ed7f5ca5737ea0a9 Mon Sep 17 00:00:00 2001
From: Philippe Pittoli <karchnu@karchnu.fr>
Date: Sat, 8 Feb 2025 18:35:56 +0100
Subject: [PATCH] Chapter 1, exercise 1, ping pong.
---
exercises/chapter1-exo1-ping.c | 76 ++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)
create mode 100644 exercises/chapter1-exo1-ping.c
diff --git a/exercises/chapter1-exo1-ping.c b/exercises/chapter1-exo1-ping.c
new file mode 100644
index 0000000..9201ee8
--- /dev/null
+++ b/exercises/chapter1-exo1-ping.c
@@ -0,0 +1,76 @@
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <stdlib.h>
+
+#define BILLION 1000000000L
+#define MILLION 1000000L
+#define THOUSAND 1000L
+
+void get_time_ts(struct timespec *t0) {
+ if (clock_gettime(CLOCK_REALTIME, t0) == -1) {
+ perror("clock_gettime");
+ exit(1);
+ }
+}
+
+long long duration_ns(struct timespec t0, struct timespec t1) {
+ return ((t1.tv_sec - t0.tv_sec)*BILLION) + (t1.tv_nsec - t0.tv_nsec);
+}
+
+void print_time_ns(long long time) {
+ printf("%llds %lldms %lldµs %lldns\n"
+ , time/BILLION
+ , (time/MILLION)%THOUSAND
+ , (time/THOUSAND)%THOUSAND
+ , time%THOUSAND
+ );
+}
+
+#define BUFSIZE 1024
+int main (int argc, char **argv) {
+ struct timespec t0, t1;
+ long long duration;
+ long long max_duration = 0;
+
+ int parent_to_child[2];
+ int child_to_parent[2];
+
+ if ( -1 == pipe(parent_to_child) ) return 1;
+ if ( -1 == pipe(child_to_parent) ) return 1;
+
+ char msg1[] = "ping";
+ char bufchild[BUFSIZE] = {0} ;
+ int nbytes;
+
+ int pid = fork();
+ switch ( pid ) {
+ case -1: return 2;
+ case 0: /*child*/
+ close(child_to_parent[0]);
+ close(parent_to_child[1]);
+ while((nbytes = read(parent_to_child[0], bufchild, BUFSIZE)) > 0) {
+ write(child_to_parent[1], bufchild, nbytes);
+ }
+ break;
+ default: /*parent*/
+ close(parent_to_child[0]);
+ close(child_to_parent[1]);
+ while (max_duration < BILLION) {
+ get_time_ts(&t0);
+ write(parent_to_child[1], msg1, strlen(msg1) + 1);
+ nbytes = read(child_to_parent[0], bufchild, BUFSIZE);
+ get_time_ts(&t1);
+ duration = duration_ns(t0, t1);
+ printf("read: %s\n", bufchild);
+ print_time_ns(duration);
+ max_duration += duration;
+ }
+ close(parent_to_child[0]);
+ close(parent_to_child[1]);
+ wait(NULL);
+ }
+ return 0;
+}