Import of the watch repository from Pebble

src/libutil/hash.c

@@ -0,0 +1,37 @@
+/*
+ * 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 "util/hash.h"
+
+#include <stdint.h>
+
+// Based on DJB2 Hash
+uint32_t hash(const uint8_t *bytes, const uint32_t length) {
+  uint32_t hash = 5381;
+
+  if (length == 0) {
+    return hash;
+  }
+
+  uint8_t c;
+  const uint8_t *last_byte = bytes + length;
+  while (bytes != last_byte) {
+    c = *bytes;
+    hash = ((hash << 5) + hash) + c;
+    bytes++;
+  }
+  return hash;
+}