Add C counterpart

author/example.c

@@ -0,0 +1,77 @@
+/* written by @kazuho */
+#include <assert.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/select.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static double now(void)
+{
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  return tv.tv_sec + (double)tv.tv_usec / 1000000;
+}
+
+static int got_usr1 = 0;
+
+static void on_sigusr1(int _unused)
+{
+  got_usr1 = 1;
+}
+
+int main(int argc, char** argv)
+{
+  sigset_t blockset, unblockset;
+  pid_t child_pid;
+  int ret;
+
+  /* setup sigsets */
+  sigemptyset(&blockset);
+  sigaddset(&blockset, SIGUSR1);
+  sigfillset(&unblockset);
+  sigdelset(&unblockset, SIGUSR1);
+
+  /* start blocking the signal */
+  sigprocmask(SIG_BLOCK, &blockset, NULL);
+
+  /* set signal handler */
+  signal(SIGUSR1, on_sigusr1);
+
+  /* create child process that sendns SIGUSR1 every 5 millisecs */
+  child_pid = fork();
+  switch (child_pid) {
+  case -1:
+    perror("fork failed");
+    exit(1);
+  case 0: /* child process */
+    kill(getppid(), SIGUSR1);
+    exit(0);
+    /* unreachable */
+  default:
+    break;
+  }
+
+  while (wait(NULL) != child_pid)
+    ;
+
+  {
+    double start_at = now(), elapsed;
+    if (! got_usr1) {
+      const static struct timespec ts = { 1, 0 };
+      ret = pselect(1, NULL, NULL, NULL, &ts, &unblockset);
+      printf("ret (should be -1): %d\n", ret);
+      printf("errno (should be EINTR(%d)): %d\n", EINTR, errno);
+    }
+    assert(got_usr1);
+    elapsed = now() - start_at;
+    assert(elapsed < 0.05);
+    got_usr1 = 0;
+  }
+
+  return 0;
+}