add function to alter the 'sum of the day'

2 files changed, 18 insertions, 0 deletions

diff --git a/easytool/easycard.c b/easytool/easycard.c
index 32c71f3..1f9572d 100644
--- a/easytool/easycard.c
+++ b/easytool/easycard.c
@@ -63,6 +63,19 @@ int easy_update_log_rec(struct easy_log_rec *elr, int16_t delta)
 	return 0;
 }
 
+/* apply a delta to the 'sum of day' record in Sector 15 Block 2 */
+int easy_update_sum_of_day(struct easy_sect15blk2 *s15b2, int16_t delta)
+{
+	int32_t sum = s15b2->sum_of_day + delta;
+
+	if (sum < 0 || sum > 0xffff)
+		return -ERANGE;
+
+	s15b2->sum_of_day = sum;
+
+	return 0;
+}
+
 static char tsbuf[64];
 char *easy_asc_timestamp(const uint8_t *timestamp)
 {
diff --git a/easytool/easycard.h b/easytool/easycard.h
index e6ce806..c421bc2 100644
--- a/easytool/easycard.h
+++ b/easytool/easycard.h
@@ -44,4 +44,9 @@ struct easy_log_rec {
 
 time_t easy_timestamp2time(const uint8_t *easy_ts);
 
+/* apply a telta (positive or negative) to a EasyCard log record */
+int easy_update_log_rec(struct easy_log_rec *elr, int16_t delta);
+/* apply a delta to the 'sum of day' record in Sector 15 Block 2 */
+int easy_update_sum_of_day(struct easy_sect15blk2 *s15b2, int16_t delta);
+
 #endif /* EASYCARD_H */