From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:53326) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RpeB3-0002ky-UP for qemu-devel@nongnu.org; Tue, 24 Jan 2012 06:04:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RpeAv-000833-54 for qemu-devel@nongnu.org; Tue, 24 Jan 2012 06:04:37 -0500 Received: from va3ehsobe005.messaging.microsoft.com ([216.32.180.31]:44695 helo=VA3EHSOBE005.bigfish.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RpeAv-00082r-2W for qemu-devel@nongnu.org; Tue, 24 Jan 2012 06:04:29 -0500 Message-ID: <4F1E8576.3060502@amd.com> Date: Tue, 24 Jan 2012 11:18:30 +0100 From: Christoph Egger MIME-Version: 1.0 References: <4F1DA926.4000709@siemens.com> <4F1DB21A.8090607@mail.berlios.de> In-Reply-To: <4F1DB21A.8090607@mail.berlios.de> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Weil Cc: Jan Kiszka , Anthony Liguori , qemu-devel , Alexander Graf On 01/23/12 20:16, Stefan Weil wrote: > Am 23.01.2012 19:38, schrieb Jan Kiszka: >> Forking an expr process for every byte of the input data slows down the >> checksum calculation massively. Fix this while still remaining portable >> by implementing the algorithm in awk. >> >> Signed-off-by: Jan Kiszka >> --- >> >> That "remaining portable" is an unproven claim. So please check that >> problematic NetBSD and also mingw. Thanks! The "unproven claim" is actually what SuSv3 spec (http://pubs.opengroup.org/onlinepubs/009695399/utilities/od.html) says: "and the output from each of the transformations shall be separated by one or more s." The actual problem is that the programmer expects the behaviour of either GNU od(1) or AT&T UNIX od(1) rather the SuSv3 spec. NetBSD has AT&T UNIX od(1). Christoph >> >> scripts/signrom.sh | 18 ++++++++---------- >> 1 files changed, 8 insertions(+), 10 deletions(-) >> >> diff --git a/scripts/signrom.sh b/scripts/signrom.sh >> index 9dc5c63..f0f460e 100755 >> --- a/scripts/signrom.sh >> +++ b/scripts/signrom.sh >> @@ -23,22 +23,20 @@ >> # did we get proper arguments? >> test "$1" -a "$2" || exit 1 >> >> -sum=0 >> - >> # find out the file size >> x=`dd if="$1" bs=1 count=1 skip=2 2>/dev/null | od -t u1 -A n` >> -#size=`expr $x \* 512 - 1` >> size=$(( $x * 512 - 1 )) >> >> # now get the checksum >> nums=`od -A n -t u1 -v -N $size "$1"` >> -for i in ${nums}; do >> - # add each byte's value to sum >> - sum=`expr \( $sum + $i \) % 256` >> -done >> - >> -sum=$(( (256 - $sum) % 256 )) >> -sum_octal=$( printf "%o" $sum ) >> +sum_octal=`echo $nums | awk 'BEGIN { >> + getline data_str; >> + sum = 0; >> + n = split(data_str, data, " "); >> + for (i = 1; i<= n; i++) >> + sum = ( sum + data[i] ) % 256; >> + printf "%o", (256 - sum) % 256; >> +}'` >> >> # and write the output file >> cp "$1" "$2" > > What about replacing the whole script by a python script? > That would save about 6 more forks :-) > > I'd prefer if we could get rid of all AWK dependencies in QEMU > and focus on as few scripting languages as reasonable. > > Regards, > Stefan W. > > -- ---to satisfy European Law for business letters: Advanced Micro Devices GmbH Einsteinring 24, 85689 Dornach b. Muenchen Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen Registergericht Muenchen, HRB Nr. 43632