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 <[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]> --- 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
