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<jan.kis...@siemens.com>
---
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 <blank>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.
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