Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755428Ab2ETNZD (ORCPT ); Sun, 20 May 2012 09:25:03 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:56920 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753710Ab2ETNX7 (ORCPT ); Sun, 20 May 2012 09:23:59 -0400 From: Akinobu Mita To: linux-kernel@vger.kernel.org, akpm@linux-foundation.org Cc: Akinobu Mita , Anders Larsen , Alasdair Kergon , dm-devel@redhat.com, linux-fsdevel@vger.kernel.org, Laurent Pinchart , linux-media@vger.kernel.org, Mark Fasheh , Joel Becker , ocfs2-devel@oss.oracle.com, Jan Kara , linux-ext4@vger.kernel.org, Andreas Dilger , "Theodore Ts'o" Subject: [PATCH 01/10] string: introduce memweight Date: Sun, 20 May 2012 22:23:14 +0900 Message-Id: <1337520203-29147-1-git-send-email-akinobu.mita@gmail.com> X-Mailer: git-send-email 1.7.7.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2862 Lines: 96 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 Cc: Anders Larsen Cc: Alasdair Kergon Cc: dm-devel@redhat.com Cc: linux-fsdevel@vger.kernel.org Cc: Laurent Pinchart Cc: linux-media@vger.kernel.org Cc: Mark Fasheh Cc: Joel Becker Cc: ocfs2-devel@oss.oracle.com Cc: Jan Kara Cc: linux-ext4@vger.kernel.org Cc: Andrew Morton Cc: Andreas Dilger Cc: "Theodore Ts'o" --- 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 #include #include +#include #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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/