locate

src/sparsemap.c

@@ -1177,3 +1177,29 @@ sparsemap_rank(sparsemap_t *map, size_t offset, size_t idx)
   }
   return (result);
 }
+
+/**
+ * Finds a span of set bits of at least |len| after |loc|. Returns the index of
+ * the n'th set bit that starts a span of at least |len| bits set to true.
+ * Returns ???TODO??? when a span of suitable length was not found.
+ */
+size_t
+sparsemap_span(sparsemap_t *map, size_t loc, size_t len)
+{
+  size_t size = 1024;
+  //  size_t size = sparsemap_get_size(map);
+  //  assert(size >= SM_SIZEOF_OVERHEAD);
+  //  if (loc + 1 > size - len || len < size) {
+  //    return size;
+  //  }
+
+  do {
+    size_t nth = sparsemap_select(map, loc, len);
+    size_t count = sparsemap_rank(map, nth - len, nth);
+    if (count == len) {
+      return nth - len;
+    }
+  } while ((loc = sparsemap_select(map, loc + 1, 1)) < size - len);
+
+  return size;
+}