altos: Add 64-bit subtraction

[fw/altos] / src / core / ao_int64.c

diff --git a/src/core/ao_int64.c b/src/core/ao_int64.c
index 5307342df90704c35e94d93880a3f42357222450..07cdb35731be63d927b963870fa56864efb1b0ac 100644 (file)
--- a/src/core/ao_int64.c
+++ b/src/core/ao_int64.c
@@ -27,6 +27,17 @@ void ao_plus64(ao_int64_t *r, ao_int64_t *a, ao_int64_t *b) {
        r->low = t;
 }
 
+void ao_minus64(ao_int64_t *r, ao_int64_t *a, ao_int64_t *b) {
+       uint32_t        t;
+
+
+       r->high = a->high - b->high;
+       t = a->low - b->low;
+       if (t > a->low)
+               r->high--;
+       r->low = t;
+}
+
 void ao_rshift64(ao_int64_t *r, ao_int64_t *a, uint8_t d) {
        if (d < 32) {
                r->low = a->low >> d;