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candump: fix off-by-one error in dropcount calculation 

Calculations using unsigned integer types are done modulo U*INT_MAX+1,
so you get the correct difference of two values by simply subtracting.
No special handling for overflow is neccessary.

Signed-off-by: Urs Thuermann <urs@isnogud.escape.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
pull/1/head
Urs Thuermann 2014-10-23 19:23:00 +02:00 committed by Oliver Hartkopp
parent 9c5bfab229
commit 0c61f2ac4c
1 changed files with 1 additions and 6 deletions
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candump.c
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@ -674,12 +674,7 @@ int main(int argc, char **argv)
/* check for (unlikely) dropped frames on this specific socket */ /* check for (unlikely) dropped frames on this specific socket */
if (dropcnt[i] != last_dropcnt[i]) { if (dropcnt[i] != last_dropcnt[i]) {
__u32 frames; __u32 frames = dropcnt[i] - last_dropcnt[i];
if (dropcnt[i] > last_dropcnt[i])
frames = dropcnt[i] - last_dropcnt[i];
else
frames = UINT32_MAX - last_dropcnt[i] + dropcnt[i];
if (silent != SILENT_ON) if (silent != SILENT_ON)
printf("DROPCOUNT: dropped %d CAN frame%s on '%s' socket (total drops %d)\n", printf("DROPCOUNT: dropped %d CAN frame%s on '%s' socket (total drops %d)\n",