1 files changed, 28 insertions, 0 deletions
diff --git a/manual/examples/timeval_subtract.c b/manual/examples/timeval_subtract.c
new file mode 100644
index 0000000..683322f
--- /dev/null
+++ b/manual/examples/timeval_subtract.c
@@ -0,0 +1,28 @@
+/* Subtract the `struct timeval' values X and Y,
+   storing the result in RESULT.
+   Return 1 if the difference is negative, otherwise 0.  */
+
+int
+timeval_subtract (result, x, y)
+     struct timeval *result, *x, *y;
+{
+  /* Perform the carry for the later subtraction by updating @var{y}. */
+  if (x->tv_usec < y->tv_usec) {
+    int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
+    y->tv_usec -= 1000000 * nsec;
+    y->tv_sec += nsec;
+  }
+  if (x->tv_usec - y->tv_usec > 1000000) {
+    int nsec = (x->tv_usec - y->tv_usec) / 1000000;
+    y->tv_usec += 1000000 * nsec;
+    y->tv_sec -= nsec;
+  }
+
+  /* Compute the time remaining to wait.
+     @code{tv_usec} is certainly positive. */
+  result->tv_sec = x->tv_sec - y->tv_sec;
+  result->tv_usec = x->tv_usec - y->tv_usec;
+
+  /* Return 1 if result is negative. */
+  return x->tv_sec < y->tv_sec;
+}