CovidBracelet/src/ens/sequencenumber.c

29 lines
785 B
C

#include "sequencenumber.h"
#define SN_MASK 0xffffff
/**
* Mask a given sequence number to get rid of MSB.
*/
#define GET_MASKED_SN(x) (x & SN_MASK)
int sn_equal(record_sequence_number_t a, record_sequence_number_t b) {
return GET_MASKED_SN(a) == GET_MASKED_SN(b);
}
record_sequence_number_t sn_increment(record_sequence_number_t sn) {
return GET_MASKED_SN(++sn);
}
record_sequence_number_t sn_increment_by(record_sequence_number_t sn, uint32_t amount) {
return GET_MASKED_SN((sn + amount));
}
record_sequence_number_t sn_get_middle_sn(record_sequence_number_t older, record_sequence_number_t newer) {
if (older <= newer) {
return GET_MASKED_SN(((older + newer) / 2));
} else {
return GET_MASKED_SN(((older + newer + SN_MASK) / 2));
}
}