From patchwork Thu Sep 23 15:41:48 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 65567 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 6B228B70FD for ; Fri, 24 Sep 2010 04:43:49 +1000 (EST) Received: from localhost ([127.0.0.1]:32820 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Oyqlm-0002K4-Ds for incoming@patchwork.ozlabs.org; Thu, 23 Sep 2010 14:43:46 -0400 Received: from [140.186.70.92] (port=59386 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OyqlF-0002Jm-9v for qemu-devel@nongnu.org; Thu, 23 Sep 2010 14:43:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OyqlD-0004Rz-KO for qemu-devel@nongnu.org; Thu, 23 Sep 2010 14:43:13 -0400 Received: from mtagate3.de.ibm.com ([195.212.17.163]:56245) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OyqlD-0004Rj-BN for qemu-devel@nongnu.org; Thu, 23 Sep 2010 14:43:11 -0400 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate3.de.ibm.com (8.13.1/8.13.1) with ESMTP id o8NFg9Fw017101 for ; Thu, 23 Sep 2010 15:42:09 GMT Received: from d12av04.megacenter.de.ibm.com (d12av04.megacenter.de.ibm.com [9.149.165.229]) by d12nrmr1607.megacenter.de.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o8NFg9H74018350 for ; Thu, 23 Sep 2010 17:42:09 +0200 Received: from d12av04.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av04.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id o8NFg9wu026477 for ; Thu, 23 Sep 2010 17:42:09 +0200 Received: from stefan-thinkpad.manchester-maybrook.uk.ibm.com (dyn-9-174-219-27.manchester-maybrook.uk.ibm.com [9.174.219.27]) by d12av04.megacenter.de.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id o8NFg8k8026447; Thu, 23 Sep 2010 17:42:09 +0200 From: Stefan Hajnoczi To: Date: Thu, 23 Sep 2010 16:41:48 +0100 Message-Id: <1285256514-21138-2-git-send-email-stefanha@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1285256514-21138-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1285256514-21138-1-git-send-email-stefanha@linux.vnet.ibm.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) Cc: Kevin Wolf , Anthony Liguori , Christoph Hellwig , Stefan Hajnoczi , Avi Kivity Subject: [Qemu-devel] [PATCH 1/7] qcow2: Make get_bits_from_size() common X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org The get_bits_from_size() calculates the log base-2 of a number. This is useful in bit manipulation code working with power-of-2s. Currently used by qcow2 and needed by qed in a follow-on patch. Signed-off-by: Stefan Hajnoczi --- block/qcow2.c | 22 ---------------------- cutils.c | 26 ++++++++++++++++++++++++++ qemu-common.h | 1 + 3 files changed, 27 insertions(+), 22 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index a53014d..72c923a 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -767,28 +767,6 @@ static int qcow2_change_backing_file(BlockDriverState *bs, return qcow2_update_ext_header(bs, backing_file, backing_fmt); } -static int get_bits_from_size(size_t size) -{ - int res = 0; - - if (size == 0) { - return -1; - } - - while (size != 1) { - /* Not a power of two */ - if (size & 1) { - return -1; - } - - size >>= 1; - res++; - } - - return res; -} - - static int preallocate(BlockDriverState *bs) { uint64_t nb_sectors; diff --git a/cutils.c b/cutils.c index 036ae3c..f9812d5 100644 --- a/cutils.c +++ b/cutils.c @@ -251,3 +251,29 @@ int fcntl_setfl(int fd, int flag) } #endif +/** + * Get the number of bits for a power of 2 + * + * The following is true for powers of 2: + * n == 1 << get_bits_from_size(n) + */ +int get_bits_from_size(size_t size) +{ + int res = 0; + + if (size == 0) { + return -1; + } + + while (size != 1) { + /* Not a power of two */ + if (size & 1) { + return -1; + } + + size >>= 1; + res++; + } + + return res; +} diff --git a/qemu-common.h b/qemu-common.h index dfd3dc0..3170c64 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -137,6 +137,7 @@ time_t mktimegm(struct tm *tm); int qemu_fls(int i); int qemu_fdatasync(int fd); int fcntl_setfl(int fd, int flag); +int get_bits_from_size(size_t size); /* path.c */ void init_paths(const char *prefix);