kern/log2: new module

2 files changed, 46 insertions, 0 deletions

diff --git a/Makefrag.am b/Makefrag.am
index 4ae58796..5d071795 100644
--- a/Makefrag.am
+++ b/Makefrag.am
@@ -25,6 +25,7 @@ x15_SOURCES +=              \
 	kern/llsync.c       \
 	kern/llsync.h       \
 	kern/llsync_i.h     \
+	kern/log2.h         \
 	kern/macros.h       \
 	kern/mutex.c        \
 	kern/mutex.h        \
diff --git a/kern/log2.h b/kern/log2.h
new file mode 100644
index 00000000..c9cc5be1
--- /dev/null
+++ b/kern/log2.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Integer base 2 logarithm operations.
+ */
+
+#ifndef _KERN_LOG2_H
+#define _KERN_LOG2_H
+
+#include <kern/assert.h>
+#include <kern/limits.h>
+
+static inline unsigned int
+ilog2(unsigned long x)
+{
+    assert(x != 0);
+    return LONG_BIT - __builtin_clzl(x) - 1;
+}
+
+static inline unsigned int
+iorder2(unsigned long size)
+{
+    assert(size != 0);
+
+    if (size == 1)
+        return 0;
+
+    return ilog2(size - 1) + 1;
+}
+
+#endif /* _KERN_LOG2_H */