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Fix divide-by-zero bug in statistics.c

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GET_LOCAL_SAC did not check if the two entries had different time stamps
and could therefore cause a divide-by-zero. x86 doesn't fault on that -
it's still wrong. This now calls a function that does proper checking of
all the values involved in the calculation.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Linus Torvalds 2013-02-20 18:57:50 -08:00 • committed by Dirk Hohndel
parent 49b4f7c4ac
commit bc5f82990d
1 changed files with 25 additions and 5 deletions
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30
profile.c
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@ -1010,12 +1010,32 @@ static void set_sac_color(struct graphics_context *gc, int sac, int avg_sac)
}
}
static double get_local_sac(struct plot_data *entry1, struct plot_data *entry2, struct dive *dive)
{
int index = entry1->cylinderindex;
int delta_time = entry2->sec - entry1->sec;
double depth;
long delta_pressure = GET_PRESSURE(entry1) - GET_PRESSURE(entry2);
long mliter;
if (entry2->cylinderindex != index)
return 0;
if (delta_pressure <= 0)
return 0;
if (delta_time <= 0)
return 0;
depth = (entry1->depth + entry2->depth) / 2.0;
mliter = dive->cylinder[index].type.size.mliter;
return delta_pressure * mliter /
(delta_time / 60.0) /
depth_to_mbar(depth, dive);
}
/* calculate the current SAC in ml/min and convert to int */
#define GET_LOCAL_SAC(_entry1, _entry2, _dive) (int) \
((GET_PRESSURE((_entry1)) - GET_PRESSURE((_entry2))) * \
(_dive)->cylinder[(_entry1)->cylinderindex].type.size.mliter / \
(((_entry2)->sec - (_entry1)->sec) / 60.0) / \
depth_to_mbar(((_entry1)->depth + (_entry2)->depth) / 2.0, (_dive)))
#define GET_LOCAL_SAC(_entry1, _entry2, _dive) \
(int) get_local_sac(_entry1, _entry2, _dive)
#define SAC_WINDOW 45 /* sliding window in seconds for current SAC calculation */