memweight() is the function that counts the total number of bits set in memory area. Unlike bitmap_weight(), memweight() takes pointer and size in bytes to specify a memory area which does not need to be aligned to long-word boundary.
Signed-off-by: Akinobu Mita <[email protected]> Cc: Anders Larsen <[email protected]> Cc: Alasdair Kergon <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Laurent Pinchart <[email protected]> Cc: [email protected] Cc: Mark Fasheh <[email protected]> Cc: Joel Becker <[email protected]> Cc: [email protected] Cc: Jan Kara <[email protected]> Cc: [email protected] Cc: Andrew Morton <[email protected]> Cc: Andreas Dilger <[email protected]> Cc: "Theodore Ts'o" <[email protected]> Cc: Matthew Wilcox <[email protected]> --- v2: simplify memweight(), adviced by Jan Kara include/linux/string.h | 3 +++ lib/string.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 35 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..bf4d5a8 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 +825,34 @@ 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; + const unsigned char *bitmap = ptr; + + for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); + bytes--, bitmap++) + w += hweight8(*bitmap); + + longs = bytes / sizeof(long); + if (longs) { + BUG_ON(longs >= INT_MAX / BITS_PER_LONG); + w += bitmap_weight((unsigned long *)bitmap, + longs * BITS_PER_LONG); + bytes -= longs * sizeof(long); + bitmap += longs * sizeof(long); + } + + for (; bytes > 0; bytes--, bitmap++) + w += hweight8(*bitmap); + + 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
