From ab53d472e785e51fdfc08fc1d66252c1153e6c0f Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Thu, 1 Jan 2009 10:12:19 +1030 Subject: bitmap: find_last_bit() Impact: New API As the name suggests. For the moment everyone uses the generic one. Signed-off-by: Rusty Russell --- lib/find_last_bit.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 lib/find_last_bit.c (limited to 'lib/find_last_bit.c') diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c new file mode 100644 index 000000000000..5d202e36bdd8 --- /dev/null +++ b/lib/find_last_bit.c @@ -0,0 +1,45 @@ +/* find_last_bit.c: fallback find next bit implementation + * + * Copyright (C) 2008 IBM Corporation + * Written by Rusty Russell + * (Inspired by David Howell's find_next_bit implementation) + * + * 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. + */ + +#include +#include +#include +#include + +unsigned long find_last_bit(const unsigned long *addr, unsigned long size) +{ + unsigned long words; + unsigned long tmp; + + /* Start at final word. */ + words = size / BITS_PER_LONG; + + /* Partial final word? */ + if (size & (BITS_PER_LONG-1)) { + tmp = (addr[words] & (~0UL >> (BITS_PER_LONG + - (size & (BITS_PER_LONG-1))))); + if (tmp) + goto found; + } + + while (words) { + tmp = addr[--words]; + if (tmp) { +found: + return words * BITS_PER_LONG + __fls(tmp); + } + } + + /* Not found */ + return size; +} +EXPORT_SYMBOL(find_last_bit); -- cgit v1.2.3