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@xxxxxxxxx> Cc: Anders Larsen <al@xxxxxxxxxxx> Cc: Alasdair Kergon <agk@xxxxxxxxxx> Cc: dm-devel@xxxxxxxxxx Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> Cc: linux-media@xxxxxxxxxxxxxxx Cc: Mark Fasheh <mfasheh@xxxxxxxx> Cc: Joel Becker <jlbec@xxxxxxxxxxxx> Cc: ocfs2-devel@xxxxxxxxxxxxxx Cc: Jan Kara <jack@xxxxxxx> Cc: linux-ext4@xxxxxxxxxxxxxxx Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx> Cc: "Theodore Ts'o" <tytso@xxxxxxx> --- 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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel