diff options
| -rw-r--r-- | include/linux/string.h | 3 | ||||
| -rw-r--r-- | lib/Makefile | 2 | ||||
| -rw-r--r-- | lib/memweight.c | 38 |
3 files changed, 42 insertions, 1 deletions
diff --git a/include/linux/string.h b/include/linux/string.h index e033564f10b..ffe0442e18d 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/Makefile b/lib/Makefile index 8c31a0cb75e..df663cc05c7 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -22,7 +22,7 @@ lib-y += kobject.o klist.o obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \ bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \ string_helpers.o gcd.o lcm.o list_sort.o uuid.o flex_array.o \ - bsearch.o find_last_bit.o find_next_bit.o llist.o + bsearch.o find_last_bit.o find_next_bit.o llist.o memweight.o obj-y += kstrtox.o obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o diff --git a/lib/memweight.c b/lib/memweight.c new file mode 100644 index 00000000000..e35fc877189 --- /dev/null +++ b/lib/memweight.c @@ -0,0 +1,38 @@ +#include <linux/export.h> +#include <linux/bug.h> +#include <linux/bitmap.h> + +/** + * 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 ret = 0; + size_t longs; + const unsigned char *bitmap = ptr; + + for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); + bytes--, bitmap++) + ret += hweight8(*bitmap); + + longs = bytes / sizeof(long); + if (longs) { + BUG_ON(longs >= INT_MAX / BITS_PER_LONG); + ret += bitmap_weight((unsigned long *)bitmap, + longs * BITS_PER_LONG); + bytes -= longs * sizeof(long); + bitmap += longs * sizeof(long); + } + /* + * The reason that this last loop is distinct from the preceding + * bitmap_weight() call is to compute 1-bits in the last region smaller + * than sizeof(long) properly on big-endian systems. + */ + for (; bytes > 0; bytes--, bitmap++) + ret += hweight8(*bitmap); + + return ret; +} +EXPORT_SYMBOL(memweight); |