fix issue 666 (#667)

* fix issue 666

* lint

benchmarks/containsmulti_benchmark.c

@@ -8,7 +8,6 @@
 
 #include "benchmark.h"
 #include "numbersfromtextfiles.h"
-#include "portability.h"
 #include "random.h"
 
 void contains_multi_via_contains(roaring_bitmap_t* bm, const uint32_t* values,

include/roaring/bitset/bitset.h

@@ -131,7 +131,10 @@ inline bool bitset_get(const bitset_t *bitset, size_t i) {
 /* Count number of bits set.  */
 size_t bitset_count(const bitset_t *bitset);
 
-/* Find the index of the first bit set. Or zero if the bitset is empty.  */
+/* Returns true if no bit is set.  */
+bool bitset_empty(const bitset_t *bitset);
+
+/* Find the index of the first bit set. Or SIZE_MAX if the bitset is empty.  */
 size_t bitset_minimum(const bitset_t *bitset);
 
 /* Find the index of the last bit set. Or zero if the bitset is empty.  */

src/bitset.c

@@ -216,14 +216,23 @@ bool bitset_inplace_union(bitset_t *CROARING_CBITSET_RESTRICT b1,
     return true;
 }
 
+bool bitset_empty(const bitset_t *bitset) {
+    for (size_t k = 0; k < bitset->arraysize; k++) {
+        if (bitset->array[k] != 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
 size_t bitset_minimum(const bitset_t *bitset) {
     for (size_t k = 0; k < bitset->arraysize; k++) {
         uint64_t w = bitset->array[k];
         if (w != 0) {
             return roaring_trailing_zeroes(w) + k * 64;
         }
     }
-    return 0;
+    return SIZE_MAX;
 }
 
 bool bitset_grow(bitset_t *bitset, size_t newarraysize) {

tests/cbitset_unit.c

@@ -60,6 +60,7 @@ void test_construct() {
 
 void test_max_min() {
     bitset_t *b = bitset_create();
+    assert_true(bitset_empty(b));
     for (size_t k = 100; k < 1000; ++k) {
         bitset_set(b, 3 * k);
         assert_true(bitset_minimum(b) == 3 * 100);