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Message-Id: <1337520203-29147-1-git-send-email-akinobu.mita@gmail.com>
Date: Sun, 20 May 2012 22:23:14 +0900
From: Akinobu Mita <akinobu.mita@...il.com>
To: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Cc: Akinobu Mita <akinobu.mita@...il.com>,
Anders Larsen <al@...rsen.net>,
Alasdair Kergon <agk@...hat.com>, dm-devel@...hat.com,
linux-fsdevel@...r.kernel.org,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
linux-media@...r.kernel.org, Mark Fasheh <mfasheh@...e.com>,
Joel Becker <jlbec@...lplan.org>, ocfs2-devel@....oracle.com,
Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
Andreas Dilger <adilger.kernel@...ger.ca>,
"Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 01/10] string: introduce memweight
memweight() is the function that counts the total number of bits set
in memory area. The memory area doesn't need to be aligned to
long-word boundary unlike bitmap_weight().
Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
Cc: Anders Larsen <al@...rsen.net>
Cc: Alasdair Kergon <agk@...hat.com>
Cc: dm-devel@...hat.com
Cc: linux-fsdevel@...r.kernel.org
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-media@...r.kernel.org
Cc: Mark Fasheh <mfasheh@...e.com>
Cc: Joel Becker <jlbec@...lplan.org>
Cc: ocfs2-devel@....oracle.com
Cc: Jan Kara <jack@...e.cz>
Cc: linux-ext4@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: "Theodore Ts'o" <tytso@....edu>
---
include/linux/string.h | 3 +++
lib/string.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+), 0 deletions(-)
diff --git a/include/linux/string.h b/include/linux/string.h
index e033564..ffe0442 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -145,4 +145,7 @@ static inline bool strstarts(const char *str, const char *prefix)
return strncmp(str, prefix, strlen(prefix)) == 0;
}
#endif
+
+extern size_t memweight(const void *ptr, size_t bytes);
+
#endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index e5878de..c8b92a0 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -26,6 +26,7 @@
#include <linux/export.h>
#include <linux/bug.h>
#include <linux/errno.h>
+#include <linux/bitmap.h>
#ifndef __HAVE_ARCH_STRNICMP
/**
@@ -824,3 +825,39 @@ void *memchr_inv(const void *start, int c, size_t bytes)
return check_bytes8(start, value, bytes % 8);
}
EXPORT_SYMBOL(memchr_inv);
+
+/**
+ * memweight - count the total number of bits set in memory area
+ * @ptr: pointer to the start of the area
+ * @bytes: the size of the area
+ */
+size_t memweight(const void *ptr, size_t bytes)
+{
+ size_t w = 0;
+ size_t longs;
+ union {
+ const void *ptr;
+ const unsigned char *b;
+ unsigned long address;
+ } bitmap;
+
+ for (bitmap.ptr = ptr; bytes > 0 && bitmap.address % sizeof(long);
+ bytes--, bitmap.address++)
+ w += hweight8(*bitmap.b);
+
+ for (longs = bytes / sizeof(long); longs > 0; ) {
+ size_t bits = min_t(size_t, INT_MAX & ~(BITS_PER_LONG - 1),
+ longs * BITS_PER_LONG);
+
+ w += bitmap_weight(bitmap.ptr, bits);
+ bytes -= bits / BITS_PER_BYTE;
+ bitmap.address += bits / BITS_PER_BYTE;
+ longs -= bits / BITS_PER_LONG;
+ }
+
+ for (; bytes > 0; bytes--, bitmap.address++)
+ w += hweight8(*bitmap.b);
+
+ return w;
+}
+EXPORT_SYMBOL(memweight);
--
1.7.7.6
--
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