Import of the watch repository from Pebble

src/fw/util/bitset.c

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "bitset.h"
+
+#include <stdint.h>
+
+uint8_t count_bits_set(uint8_t *bitset_bytes, int num_bits) {
+  uint8_t num_bits_set = 0;
+  int num_bytes = (num_bits + 7) / 8;
+  if ((num_bits % 8) != 0) {
+    bitset_bytes[num_bytes] &= ((0x1 << (num_bits)) - 1);
+  }
+
+  for (int i = 0; i < num_bytes; i++) {
+    num_bits_set += __builtin_popcount(bitset_bytes[i]);
+  }
+
+  return (num_bits_set);
+}