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AP_RangeFinder: Ensure no divide by zeros in LeddarOne

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Having a critical divide by value as a class member that could change external to the function using it is fragile. It was not very obvious that a divide by zero was not possible in the current design, now it's very obvious and safer in case the code changes later.
This commit is contained in:
Tom Pittenger 2016-09-19 02:42:06 -07:00 committed by Randy Mackay
parent b6867e085d
commit e928e20b11
2 changed files with 8 additions and 5 deletions
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12
libraries/AP_RangeFinder/AP_RangeFinder_LeddarOne.cpp
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@ -68,12 +68,16 @@ bool AP_RangeFinder_LeddarOne::get_reading(uint16_t &reading_cm)
}
// parse a response message, set detections and sum_distance
if (parse_response() <= 0) {
// must be signed to handle errors
int8_t number_detections = parse_response();
if (number_detections <= 0) {
// TODO: when (number_detections < 0) handle LEDDARONE_ERR_
return false;
}
// calculate average distance
reading_cm = sum_distance / number_detections;
reading_cm = sum_distance / (uint8_t)number_detections;
return true;
}
@ -204,7 +208,7 @@ int8_t AP_RangeFinder_LeddarOne::parse_response(void)
}
// number of detections
number_detections = data_buffer[10];
uint8_t number_detections = data_buffer[10];
// if the number of detection is over , it is false
if (number_detections > (sizeof(detections) / sizeof(detections[0]))) {
@ -220,5 +224,5 @@ int8_t AP_RangeFinder_LeddarOne::parse_response(void)
index_offset += 4;
}
return number_detections;
return (int8_t)number_detections;
}

1
libraries/AP_RangeFinder/AP_RangeFinder_LeddarOne.h
View File

@ -47,6 +47,5 @@ private:
uint32_t last_reading_ms = 0;
uint16_t detections[3];
uint8_t number_detections = 0;
uint32_t sum_distance = 0;
};