ntptimestamp.c

00001 #include <stdint.h>
00002 #include <stdbool.h>
00003 
00004 #include "clktime.h"
00005 #include "clkutc.h"
00006 
00007 #define SECONDS_BETWEEN_1900_AND_1970 2208988800ULL
00008 
00009 #define ERA_BASE_LOW 1LL //Adjust this from 0 to 1 between 1968 and 2036; 1 to 2 between 2104 and 2168
00010 #define ERA_BASE_HGH 0LL //Adjust this from 0 to 1 between 2036 and 2104; 1 to 2 between 2172 and 2240
00011 
00012 uint64_t NtpTimeStampFromClkTime(clktime tai)
00013 {
00014     clktime utc = ClkUtcFromTai(tai);
00015     uint64_t timestamp = utc << (32 - CLK_TIME_ONE_SECOND_SHIFT);
00016     
00017     timestamp += SECONDS_BETWEEN_1900_AND_1970 << 32; //This should just wrap around the unsigned timestamp removing the unwanted era.
00018     
00019     return timestamp;
00020 }
00021 clktime NtpTimeStampToClkTime(uint64_t timestamp)
00022 {
00023     bool isHigh = (timestamp & (1ULL << 63)) != 0;
00024     
00025     clktime utc = timestamp - (SECONDS_BETWEEN_1900_AND_1970 << 32);
00026     utc >>= (32 - CLK_TIME_ONE_SECOND_SHIFT);
00027     
00028     //Correct for era
00029     if (isHigh) utc += ERA_BASE_HGH << (32 + CLK_TIME_ONE_SECOND_SHIFT);
00030     else        utc += ERA_BASE_LOW << (32 + CLK_TIME_ONE_SECOND_SHIFT);
00031     
00032     clktime tai = ClkUtcToTai(utc);
00033     
00034     return tai;
00035 }
00036