From a36c6426dacf7e0d3e69fb3089a2423420ac9990 Mon Sep 17 00:00:00 2001 From: Richard Braun Date: Sat, 23 Jan 2016 19:42:01 +0100 Subject: Import the log2 module from X15 and relicense to GPLv2+ * kern/log2.h: New file. --- kern/log2.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 kern/log2.h (limited to 'kern/log2.h') diff --git a/kern/log2.h b/kern/log2.h new file mode 100644 index 00000000..0e67701c --- /dev/null +++ b/kern/log2.h @@ -0,0 +1,50 @@ +/* + * 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 2 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 . + * + * + * Integer base 2 logarithm operations. + */ + +#ifndef _KERN_LOG2_H +#define _KERN_LOG2_H + +#include + +#ifdef __LP64__ +#define LONG_BIT 64 +#else /* __LP64__ */ +#define LONG_BIT 32 +#endif /* __LP64__ */ + +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 */ -- cgit v1.2.3