Merge branch 'traps' into cow

Conflicts:
	.gitignore
	Makefile
	conf/lab.mk

1 files changed, 44 insertions, 0 deletions

diff --git a/user/pingpong.c b/user/pingpong.c
new file mode 100644
index 0000000..7b03a76
--- /dev/null
+++ b/user/pingpong.c
@@ -0,0 +1,44 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int
+main(int argc, char* argv[])
+{
+  int p[2];
+
+  if (argc > 1) {
+    fprintf(2, "usage: pingpong\n");
+    exit(1);
+  }
+
+  pipe(p);
+
+  int pid = fork();
+
+  if (pid == 0) {
+    short n;
+    read(p[0], &n, sizeof(n));
+    if (n == 42) {
+      fprintf(1, "%d: received ping\n", getpid());
+    }
+    n++;
+    write(p[1], &n, sizeof(n));
+    close(p[0]);
+    close(p[1]);
+    exit(0);
+  }
+
+  short n = 42;
+
+  write(p[1], &n, sizeof(n));
+  read(p[0], &n, sizeof(n));
+  if (n == 43) {
+    fprintf(1, "%d: received pong\n", getpid());
+  }
+  close(p[0]);
+  close(p[1]);
+
+  wait(0);
+
+  exit(0);
+}