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.m...@gmail.com>
Cc: Anders Larsen <a...@alarsen.net>
Cc: Alasdair Kergon <a...@redhat.com>
Cc: dm-de...@redhat.com
Cc: linux-fsde...@vger.kernel.org
Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
Cc: linux-media@vger.kernel.org
Cc: Mark Fasheh <mfas...@suse.com>
Cc: Joel Becker <jl...@evilplan.org>
Cc: ocfs2-de...@oss.oracle.com
Cc: Jan Kara <j...@suse.cz>
Cc: linux-e...@vger.kernel.org
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Andreas Dilger <adilger.ker...@dilger.ca>
Cc: "Theodore Ts'o" <ty...@mit.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
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
