lib/timeutils: Provide simple impl of extra funcs when Epoch is 1970.

Dates/times must be post 2000/1/1 to work correctly with these simple
implementations.
Signed-off-by: Damien George <damien@micropython.org>

lib/timeutils/timeutils.c

@@ -158,7 +158,7 @@ mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
         + (year - 2000) * 31536000;
 }
 
-mp_uint_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
     mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
 
     // Normalize the tuple. This allows things like:

lib/timeutils/timeutils.h

@@ -52,12 +52,21 @@ void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t,
 mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
     mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second);
 
-mp_uint_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
     mp_int_t hours, mp_int_t minutes, mp_int_t seconds);
 
 // Select the Epoch used by the port.
 #if MICROPY_EPOCH_IS_1970
 
+static inline void timeutils_seconds_since_epoch_to_struct_time(uint64_t t, timeutils_struct_time_t *tm) {
+    // TODO this will give incorrect results for dates before 2000/1/1
+    return timeutils_seconds_since_2000_to_struct_time(t - TIMEUTILS_SECONDS_1970_TO_2000, tm);
+}
+
+static inline uint64_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday, mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
+    return timeutils_mktime_2000(year, month, mday, hours, minutes, seconds) + TIMEUTILS_SECONDS_1970_TO_2000;
+}
+
 static inline uint64_t timeutils_seconds_since_epoch(mp_uint_t year, mp_uint_t month,
     mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
     return timeutils_seconds_since_2000(year, month, date, hour, minute, second) + TIMEUTILS_SECONDS_1970_TO_2000;
@@ -75,6 +84,7 @@ static inline uint64_t timeutils_nanoseconds_since_epoch_to_nanoseconds_since_19
 
 #define timeutils_seconds_since_epoch_to_struct_time timeutils_seconds_since_2000_to_struct_time
 #define timeutils_seconds_since_epoch timeutils_seconds_since_2000
+#define timeutils_mktime timeutils_mktime_2000
 
 static inline uint64_t timeutils_seconds_since_epoch_to_nanoseconds_since_1970(mp_uint_t s) {
     return ((uint64_t)s + TIMEUTILS_SECONDS_1970_TO_2000) * 1000000000ULL;