nimble/porting: Add util.h

This might be useful for portings.

porting/nimble/include/os/util.h

@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+#ifndef H_OS_UTIL_
+#define H_OS_UTIL_
+
+/* Helpers to pass integers as pointers and vice-versa */
+#define POINTER_TO_UINT(p) ((unsigned int) ((uintptr_t) (p)))
+#define UINT_TO_POINTER(u) ((void *) ((uintptr_t) (u)))
+#define POINTER_TO_INT(p) ((int) ((intptr_t) (p)))
+#define INT_TO_POINTER(u) ((void *) ((intptr_t) (u)))
+
+/* Helper to retrieve pointer to "parent" object in structure */
+#define CONTAINER_OF(ptr, type, field) \
+        ((type *)(((char *)(ptr)) - offsetof(type, field)))
+
+/* Helper to calculate number of elements in array */
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(array) \
+        (sizeof(array) / sizeof((array)[0]))
+#endif
+#endif