[lib][cbuf] simple circular buffer implementation
diff --git a/include/pow2.h b/include/pow2.h
new file mode 100644
index 0000000..1ab8ae0
--- /dev/null
+++ b/include/pow2.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2008 Travis Geiselbrecht
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef __POW2_H
+#define __POW2_H
+
+#include <sys/types.h>
+#include <compiler.h>
+
+/* routines for dealing with power of 2 values for efficiency */
+static inline __ALWAYS_INLINE bool ispow2(uint val)
+{
+ return ((val - 1) & val) == 0;
+}
+
+static inline __ALWAYS_INLINE uint log2(uint val)
+{
+ if (!ispow2(val))
+ return 0; // undefined
+
+ return __builtin_ctz(val);
+}
+
+static inline __ALWAYS_INLINE uint valpow2(uint valp2)
+{
+ return 1 << valp2;
+}
+
+static inline __ALWAYS_INLINE uint divpow2(uint val, uint divp2)
+{
+ return val >> divp2;
+}
+
+static inline __ALWAYS_INLINE uint modpow2(uint val, uint modp2)
+{
+ return val & ((1UL << modp2) - 1);
+}
+
+
+#endif
+