On Wed, May 23, 2012 at 09:12:18PM +0900, Akinobu Mita wrote: > size_t memweight(const void *ptr, size_t bytes) Why should this return size_t instead of unsigned long? > { > 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); > 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; > } bitmap_weight copes with a bitmask that isn't a multiple of BITS_PER_LONG in size already. So I think this can be done as: unsigned long memweight(const void *s, size_t n) { const unsigned char *ptr = s; unsigned long r = 0; while (n > 0 && (unsigned long)ptr % sizeof(long)) { r += hweight8(*ptr); n--; ptr++; } BUG_ON(n >= INT_MAX / 8) return r + bitmap_weight((unsigned long *)ptr, n * 8); } -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel