1 files changed, 52 insertions, 0 deletions
diff --git a/user/pingpong.c b/user/pingpong.c
new file mode 100644
index 0000000..6ed12e7
--- /dev/null
+++ b/user/pingpong.c
@@ -0,0 +1,52 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+#define N 5
+char buf[N];
+
+void
+pong(int *parent_to_child, int *child_to_parent) {
+  if (read(parent_to_child[0], buf, N) < 0) {
+    printf("read failed\n");
+  }
+  printf("%d: received %s\n", getpid(), buf);
+  if (write(child_to_parent[1], "pong", 4) != 4) {
+    printf("write failed\n");
+  }
+}
+
+void
+ping(int *parent_to_child, int *child_to_parent) {
+  
+  if (write(parent_to_child[1], "ping", 4) != 4) {
+    printf("write failed\n");
+  }
+  if (read(child_to_parent[0], buf, N) < 0) {
+    printf("read failed\n");
+  }
+  printf("%d: received %s\n", getpid(), buf);
+}
+
+int
+main(int argc, char *argv[])
+{
+  int parent_to_child[2];
+  int child_to_parent[2];
+
+  int pid;
+
+  if (pipe(parent_to_child) < 0 || pipe(child_to_parent) < 0) {
+    printf("pipe failed\n");
+  }
+  if ((pid = fork()) < 0) {
+    printf("fork failed\n");
+  }
+  if (pid == 0) {
+    pong(parent_to_child, child_to_parent);
+  } else {
+    ping(parent_to_child, child_to_parent);
+  }
+  
+  exit(0);
+}