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timestamp.c
184 lines (155 loc) · 5.59 KB
/
timestamp.c
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#include "aprx.h"
/* Time Base Conversion Macros
*
* The NTP timebase is 00:00 Jan 1 1900. The local
* time base is 00:00 Jan 1 1970. Convert between
* these two by added or substracting 70 years
* worth of time. Note that 17 of these years were
* leap years.
*/
#define TIME_BASEDIFF (((70U*365U + 17U) * 24U*3600U))
#define TIME_NTP_TO_LOCAL(t) ((t)-TIME_BASEDIFF)
#define TIME_LOCAL_TO_NTP(t) ((t)+TIME_BASEDIFF)
typedef struct ntptime {
uint32_t seconds;
uint32_t fraction;
} ntptime_t;
uint64_t unix_tv_to_ntp(struct timeval *tv) {
// Reciprocal conversion of tv_usec to fractional NTP seconds
// Multiply tv_usec by (2^64)/1_000_000
// GCC optimized this nicely on i386
uint64_t fract = 18446744073709ULL * (uint32_t)(tv->tv_usec);
// Scale it back by 32 bit positions
fract >>= 32;
// Straight-forward conversion of tv_sec to NTP seconds
uint64_t ntptime = TIME_LOCAL_TO_NTP(tv->tv_sec);
ntptime <<= 32;
return ntptime + fract;
}
void unix_tv_to_ntp4(struct timeval *tv, ntptime_t *ntp) {
// Reciprocal conversion of tv_usec to fractional NTP seconds
// Multiply tv_usec by ((2^64)/1_000_000) / (2^32)
// GCC optimized this nicely on i386, and 64-bit machines
uint32_t fract = (18446744073709ULL * (uint32_t)(tv->tv_usec)) >> 32;
//
// movl 4(%ebx), %eax
// imull $4294, %eax, %esi ;; 32*32->32 --> %esi
// movl $-140462611, %edi
// mull %edi ;; 32*32->64 --> %edx:eax
// addl %edx, %esi ;; sum %esi + %edx
//
ntp->fraction = fract;
// Straight-forward conversion of tv_sec to NTP seconds
ntp->seconds = TIME_LOCAL_TO_NTP(tv->tv_sec);
}
void unix_tv_to_ntp4a(struct timeval *tv, ntptime_t *ntp) {
// Reciprocal conversion of tv_usec to fractional NTP seconds
// Multiply tv_usec by ((2^64)/1_000_000) / (2^32)
// GCC optimizes this slightly better for ARM, than ntp4()
// .. for i386 ntp4() and ntp4a() are equal.
uint64_t fract = 18446744073709ULL * (uint32_t)(tv->tv_usec);
// Scale it back by 32 bit positions
fract >>= 32;
ntp->fraction = (uint32_t)fract;
// Straight-forward conversion of tv_sec to NTP seconds
ntp->seconds = TIME_LOCAL_TO_NTP(tv->tv_sec);
}
uint64_t unix_tv_to_ntp2(struct timeval *tv) {
uint64_t tt = TIME_LOCAL_TO_NTP(tv->tv_sec);
tt <<= 32;
uint64_t tu = tv->tv_usec;
tu <<= 32;
// Following causes gcc to call __udivdi3()
// on 32-bit machines
tu /= 1000000; // Fixed point scaling..
return (tt + tu);
}
// static const double usec2NtpFract = 4294.9672960D; // 2^32 / 1E6
uint64_t unix_tv_to_ntp3(struct timeval *tv) {
uint64_t tt = TIME_LOCAL_TO_NTP(tv->tv_sec);
tt <<= 32;
// FP math is bad on embedded systems...
// double fract = usec2NtpFract * (uint32_t)tv->tv_usec;
// tt += (int64_t)fract;
return tt;
}
static const char *BASE64EncodingDictionary =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789"
"+/";
void encode_aprsis_ntptimestamp(uint64_t ntptime, char timestamp[8])
{
int i;
ntptime >>= 22; // scale to 1/1024 seconds
for (i = 6; i >= 0; --i) {
int n = (((int)ntptime) & 0x3F); // lowest 6 bits
// printf(" [n=%d]\n", n);
ntptime >>= 6;
timestamp[i] = BASE64EncodingDictionary[n];
}
timestamp[7] = 0;
}
static const int8_t BASE64DecodingDictionary[128] =
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, // ' ', '!', '"', '#'
-1, -1, -1, -1, // '$', '%', '&'', '\''
-1, -1, -1, 62, // '(', ')', '*', '+',
-1, -1, -1, 63, // ',', '-', '.', '/'
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // '0' .. '9'
-1, -1, -1, -1, -1, -1, // ':', ';', '<', '=', '>', '?'
-1, 0, 1, 2, 3, 4, 5, 6, // '@', 'A' .. 'G'
7, 8, 9, 10, 11, 12, 13, 14, // 'H' .. 'O'
15, 16, 17, 18, 19, 20, 21, 22, // 'P' .. 'W'
23, 24, 25, -1, -1, -1, -1, -1, // 'X'..'Z', '[', '\\', ']', '^', '_'
-1, 26, 27, 28, 29, 30, 31, 32, // '`', 'a' .. 'g'
33, 34, 35, 36, 37, 38, 39, 40, // 'h' .. 'o'
41, 42, 43, 44, 45, 46, 47, 48, // 'p' .. 'w'
49, 50, 51, -1, -1, -1, -1, -1 }; // 'x'..'z', ...
int decode_aprsis_ntptimestamp(char timestamp[8], uint64_t *ntptimep)
{
uint64_t ntptime = 0;
int i, n;
char c;
for (i = 0; i < 7; ++i) {
c = timestamp[i];
if (c <= 0 || c > 127) return -1; // BARF!
n = BASE64DecodingDictionary[(int)c];
// printf(" [n=%d]\n", n);
if (n < 0) {
// Should not happen!
return -1; // Decode fail!
}
ntptime <<= 6;
ntptime |= n;
}
ntptime <<= 22;
*ntptimep = ntptime;
return 0; // Decode OK
}
#ifdef TESTING
int main(int argc, char *argv[]) {
struct timeval tv;
char timestamp[8];
uint64_t ntptime;
ntptime_t ntp_time;
// gettimeofday(&tv, NULL);
// Example time.. (refvalue: NTPseconds!)
tv.tv_sec = TIME_NTP_TO_LOCAL(3484745636U); tv.tv_usec = 709603U;
ntptime = unix_tv_to_ntp(&tv);
printf("NTPtime1 = %08x.%08x \n", (uint32_t)(ntptime >> 32), (uint32_t)ntptime);
ntptime = unix_tv_to_ntp2(&tv);
printf("NTPtime2 = %08x.%08x \n", (uint32_t)(ntptime >> 32), (uint32_t)ntptime);
// ntptime = unix_tv_to_ntp3(&tv);
// printf("NTPtime3 = %08x.%08x \n", (uint32_t)(ntptime >> 32), (uint32_t)ntptime);
unix_tv_to_ntp4(&tv, &ntp_time);
printf("NTPtime4 = %08x.%08x \n", ntp_time.seconds, ntp_time.fraction);
encode_aprsis_ntptimestamp( ntptime, timestamp );
printf("Timestamp = %s\n", timestamp);
int rc = decode_aprsis_ntptimestamp( timestamp, &ntptime );
printf("Decode rc=%d\n", rc);
printf("NTPtime = %08x.%08x \n", (uint32_t)(ntptime >> 32), (uint32_t)ntptime);
return 0;
}
#endif