From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761451AbYESRFT (ORCPT ); Mon, 19 May 2008 13:05:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754062AbYESRFF (ORCPT ); Mon, 19 May 2008 13:05:05 -0400 Received: from visualserver.org ([84.242.66.126]:39789 "EHLO visualserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754039AbYESRFD (ORCPT ); Mon, 19 May 2008 13:05:03 -0400 X-Greylist: delayed 321 seconds by postgrey-1.27 at vger.kernel.org; Mon, 19 May 2008 13:05:03 EDT Date: Mon, 19 May 2008 19:04:55 +0200 (CEST) From: Soumyadip Das Mahapatra To: linux-kernel@vger.kernel.org cc: akinobu.mita@gmail.com Subject: [PATCH 1/2] bitreversal program Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-visualserver.org-MailScanner-Information: Please contact the ISP for more information X-MailScanner-ID: C57A82FB42.3C4F8 X-visualserver.org-MailScanner: Found to be clean X-visualserver.org-MailScanner-From: kernelhacker@visualserver.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --- a/include/linux/bitrev.h 2008-04-17 08:19:44.000000000 +0530 +++ b/include/linux/bitrev.h 2008-05-19 21:49:46.000000000 +0530 @@ -3,11 +3,32 @@ #include -extern u8 const byte_rev_table[256]; +/** + * Here is a generalised bit reversal program + * @x: word to get bits reversed + * @k: key, explained below + * for k = 31, it reverses the bits of word(32 bit) + * for k = 24, it reverses the bytes in word + * for k = 7, it reverses the bits in every byte without + * changing the positions of bytes in a word + * and for k = 16 it swaps the left and right halves of a + * word + */ -static inline u8 bitrev8(u8 byte) +static inline u32 gen_bit_rev(u32 x, u32 k) { - return byte_rev_table[byte]; + if(k & 1) + x = (x & 0x55555555) << 1 | (x & 0xaaaaaaaa) >> 1; + if(k & 2) + x = (x & 0x33333333) << 2 | (x & 0xcccccccc) >> 2; + if(k & 4) + x = (x & 0x0f0f0f0f) << 4 | (x & 0xf0f0f0f0) >> 4; + if(k & 8) + x = (x & 0x00ff00ff) << 8 | (x & 0xff00ff00) >> 8; + if(k & 16) + x = (x & 0x0000ffff) << 16 | (x & 0xffff0000) >> 16; + + return x; } extern u32 bitrev32(u32 in); -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.