string: introduce memweight() (639b9e34) · Commits · 戴 / test

include/linux/string.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -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_ */

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

0 → 100644

+38 −0

Original line number	Diff line number	Diff line
		#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);