jepler/wwvbdecode-2011
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implementing and testing DST handling

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This commit is contained in:
Jeff Epler 2021-10-25 08:21:33 -05:00
parent 5f4133f0dc
commit 633a6a9378
1 changed files with 73 additions and 17 deletions
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90
wwvbdecode.cc
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@ -7,6 +7,34 @@
#define printf(...) (0)
#endif
/* Timezone setting
*
* If you are not in US/Central timezone, you'll have to modify this.
*
* standard and dst give the offsets during standard and dst times,
* respectively.
*
* apply_standard and apply_dst give the UTC minute of the day to start standard
* or dst time.
*
* You can use the unix 'zdump' program to see these values for your timezone:
* $ zdump -v -c 2010,2011 US/Central
* ...
* US/Central Sun Mar 14 08:00:00 2010 UTC = Sun Mar 14 03:00:00 2010 CDT isdst=1 gmtoff=-18000
* US/Central Sun Nov 7 07:00:00 2010 UTC = Sun Nov 7 01:00:00 2010 CST isdst=0 gmtoff=-21600
* ..
* From the gmtoff values in seconds, you can determine the hours and minutes of
* offset for standard and dst. If the minute offset is nonzero and the hour
* offset is negative, then the minute offset should be negative too. (e.g.,
* subtract 6 hours and then subtract 30 minutes).
*
* From the UTC transition times, you can directly read the values for
* apply_standard and apply_dst.
*/
struct tzoffset { int8_t hour, minute; };
const tzoffset standard = { -6, 0 }, apply_standard = { 7, 0 };
const tzoffset dst = { -5, 0 }, apply_dst = {8, 0};
struct wwvb_t {
int16_t yday; // 1..365, or 1..366 in leap years
int8_t hour; // 0..23
@ -91,7 +119,7 @@ void advance_second(wwvb_t &t) {
// in minutes and seconds. Note: for negative non-hour offsets, h and m
// should both be negative. e.g., for instance the NST offset of -3:30
// would be passed as h=-3, m=-30
void apply_tz(wwvb_t &t, int8_t h, int8_t m) {
void offset_tz(wwvb_t &t, int8_t h, int8_t m) {
t.minute += m;
t.hour += h;
// Now, both hours and minutes can be outside their normal range
@ -129,6 +157,29 @@ void apply_tz(wwvb_t &t, int8_t h, int8_t m) {
// Now
}
bool isdst(wwvb_t &t)
{
switch(t.dst)
{
case 0: return false;
case 3: return true;
case 2: // dst begins today
if(t.hour > apply_dst.hour) return true;
if(t.hour < apply_dst.hour) return false;
return t.minute >= apply_dst.minute;
case 1: // dst ends today
if(t.hour > apply_standard.hour) return false;
if(t.hour < apply_standard.hour) return true;
return t.minute < apply_standard.minute;
}
}
void apply_tz(wwvb_t &t)
{
if(isdst(t)) offset_tz(t, dst.hour, dst.minute);
else offset_tz(t, standard.hour, standard.minute);
}
int8_t leapyears_before(int8_t year) {
return (year + 3) / 4;
}
@ -434,14 +485,12 @@ printf("wwvb_receive_loop %c %4d %d %8d\n",
return;
set_state_capture_time:
printf("->capture time\n");
counter = 0;
memset(wwvb_buf, 0, sizeof(wwvb_buf));
wwvb_state = STATE_CAPTURE_TIME;
return;
set_state_find_polarity:
printf("->find_polarity\n");
sos_counter = 0;
wwvb_state = STATE_FIND_POLARITY;
return;
@ -451,33 +500,40 @@ printf("->find_polarity\n");
#include <stdio.h>
#include <stdlib.h>
bool time_valid;
wwvb_t now;
void set_time(const wwvb_t &t) {
printf("set time %d/%03d %d:%02d:%02d ly=%d ls=%d dst=%d\n",
if(time_valid) return;
printf("set time %d/%03d %2d:%02d:%02d ly=%d ls=%d dst=%d\n",
t.year + 2000, t.yday, t.hour, t.minute, t.second, t.ls, t.ly, t.dst);
exit(0);
now = t;
time_valid = true;
}
void set_divisor(uint32_t div) {}
void next_second() {}
void next_second() {
if(!time_valid) return;
advance_second(now);
if(now.second == 0 || now.second >= 59)
{
wwvb_t t = now;
printf("%d/%03d %2d:%02d:%02d.%04d ly=%d ls=%d dst=%d ",
t.year + 2000, t.yday, t.hour, t.minute, t.second, free_running_ms, t.ls, t.ly, t.dst);
apply_tz(t);
printf("%d/%03d %2d:%02d:%02d.%04d C%cT\n",
t.year + 2000, t.yday, t.hour, t.minute, t.second, free_running_ms, isdst(now) ? 'D' : 'S');
}
}
int main() {
wwvb_t t0 = { 1, 1, 30, 0, 0, 0, 0, 0 },
t1 = { 2, 1, 30, 0, 0, 0, 0, 0 },
t2 = { 3, 1, 30, 0, 0, 0, 0, 0 };
ticks = 0;
steer_timer(t0);
ticks = 86401234;
steer_timer(t1);
ticks += 86400001;
steer_timer(t2);
while(1) {
int c = getchar();
if(c == EOF) break;
wwvb_receive_loop(c == '1');
}
printf("failed to set time\n");
if(!time_valid) printf("failed to set time\n");
}
#else
#include <stdio.h>