RTC: pull rtc code into own file for cleanup

src/gps/RTC.cpp

@@ -0,0 +1,72 @@
+#include "configuration.h"
+#include "RTC.h"
+#include <sys/time.h>
+#include <time.h>
+
+bool timeSetFromGPS; // We try to set our time from GPS each time we wake from sleep
+
+// stuff that really should be in in the instance instead...
+static uint32_t
+    timeStartMsec; // Once we have a GPS lock, this is where we hold the initial msec clock that corresponds to that time
+static uint64_t zeroOffsetSecs; // GPS based time in secs since 1970 - only updated once on initial lock
+
+void readFromRTC()
+{
+    struct timeval tv; /* btw settimeofday() is helpfull here too*/
+
+    if (!gettimeofday(&tv, NULL)) {
+        uint32_t now = millis();
+
+        DEBUG_MSG("Read RTC time as %ld (cur millis %u) valid=%d\n", tv.tv_sec, now, timeSetFromGPS);
+        timeStartMsec = now;
+        zeroOffsetSecs = tv.tv_sec;
+    }
+}
+
+/// If we haven't yet set our RTC this boot, set it from a GPS derived time
+bool perhapsSetRTC(const struct timeval *tv)
+{
+    if (!timeSetFromGPS) {
+        timeSetFromGPS = true;
+        DEBUG_MSG("Setting RTC %ld secs\n", tv->tv_sec);
+#ifndef NO_ESP32
+        settimeofday(tv, NULL);
+#else
+        DEBUG_MSG("ERROR TIME SETTING NOT IMPLEMENTED!\n");
+#endif
+        readFromRTC();
+        return true;
+    } else {
+        return false;
+    }
+}
+
+bool perhapsSetRTC(struct tm &t)
+{
+    /* Convert to unix time
+    The Unix epoch (or Unix time or POSIX time or Unix timestamp) is the number of seconds that have elapsed since January 1, 1970
+    (midnight UTC/GMT), not counting leap seconds (in ISO 8601: 1970-01-01T00:00:00Z).
+    */
+    time_t res = mktime(&t);
+    struct timeval tv;
+    tv.tv_sec = res;
+    tv.tv_usec = 0; // time.centisecond() * (10 / 1000);
+
+    // DEBUG_MSG("Got time from GPS month=%d, year=%d, unixtime=%ld\n", t.tm_mon, t.tm_year, tv.tv_sec);
+    if (t.tm_year < 0 || t.tm_year >= 300) {
+        // DEBUG_MSG("Ignoring invalid GPS month=%d, year=%d, unixtime=%ld\n", t.tm_mon, t.tm_year, tv.tv_sec);
+        return false;
+    } else {
+        return perhapsSetRTC(&tv);
+    }
+}
+
+uint32_t getTime()
+{
+    return ((millis() - timeStartMsec) / 1000) + zeroOffsetSecs;
+}
+
+uint32_t getValidTime()
+{
+    return timeSetFromGPS ? getTime() : 0;
+}