util: New function bitwise_is_all_zeros().

Signed-off-by: Ben Pfaff <blp@nicira.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/test-util.c b/tests/test-util.c
index ed98295b..23b86e8c 100644
--- a/tests/test-util.c
+++ b/tests/test-util.c
@@ -184,6 +184,51 @@ check_bitwise_one(void)
     }
 }
 
+static void
+check_bitwise_is_all_zeros(void)
+{
+    int n_loops;
+
+    n_loops = 0;
+    for (n_loops = 0; n_loops < 100; n_loops++) {
+        ovs_be64 x = htonll(0);
+        int i;
+
+        for (i = 0; i < 64; i++) {
+            ovs_be64 bit;
+            int ofs, n;
+
+            /* Change a random 0-bit into a 1-bit. */
+            do {
+                bit = htonll(UINT64_C(1) << (random_uint32() % 64));
+            } while (x & bit);
+            x |= bit;
+
+            for (ofs = 0; ofs < 64; ofs++) {
+                for (n = 0; n <= 64 - ofs; n++) {
+                    bool expect;
+                    bool answer;
+
+                    expect = (n == 64
+                              ? x == 0
+                              : !(x & htonll(((UINT64_C(1) << n) - 1)
+                                             << ofs)));
+                    answer = bitwise_is_all_zeros(&x, sizeof x, ofs, n);
+                    if (expect != answer) {
+                        fprintf(stderr,
+                                "bitwise_is_all_zeros(0x%016"PRIx64",8,%d,%d "
+                                "returned %s instead of %s\n",
+                                ntohll(x), ofs, n,
+                                answer ? "true" : "false",
+                                expect ? "true" : "false");
+                        abort();
+                    }
+                }
+            }
+        }
+    }
+}
+
 int
 main(void)
 {
@@ -213,5 +258,7 @@ main(void)
 
     check_bitwise_one();
 
+    check_bitwise_is_all_zeros();
+
     return 0;
 }