shared/timeutils: Standardize supported date range on all platforms.

This is code makes sure that time functions work properly on a
reasonable date range, on all platforms, regardless of the epoch.
The suggested minimum range is 1970 to 2099.

In order to reduce code footprint, code to support far away dates
is only enabled specified by the port.

New types are defined to identify timestamps.

The implementation with the smallest code footprint is when
support timerange is limited to 1970-2099 and Epoch is 1970.
This makes it possible to use 32 bit unsigned integers for
all timestamps.

On ARM4F, adding support for dates up to year 3000 adds
460 bytes of code. Supporting dates back to 1600 adds
another 44 bytes of code.

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/py/mpconfig.h b/py/mpconfig.h
index cf0538cae..4c1276275 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -893,6 +893,64 @@ typedef double mp_float_t;
 #define MICROPY_FULL_CHECKS (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_CORE_FEATURES)
 #endif
 
+// Ports can choose to use timestamps based on 2000-01-01 or 1970-01-01
+// Default is timestamps based on 2000-01-01
+#if !defined(MICROPY_EPOCH_IS_2000) && !defined(MICROPY_EPOCH_IS_1970)
+#define MICROPY_EPOCH_IS_2000 (1)
+#define MICROPY_EPOCH_IS_1970 (0)
+#elif !defined(MICROPY_EPOCH_IS_1970)
+#define MICROPY_EPOCH_IS_1970 (1 - (MICROPY_EPOCH_IS_2000))
+#elif !defined(MICROPY_EPOCH_IS_2000)
+#define MICROPY_EPOCH_IS_2000 (1 - (MICROPY_EPOCH_IS_1970))
+#endif
+
+// To maintain reasonable compatibility with CPython on embedded systems,
+// and avoid breaking anytime soon, time functions are defined to work
+// at least between 1970 and 2099 (included) on any machine.
+//
+// Specific ports can enable extended date support
+// - after 2099 using MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND
+// - before 1970 using MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+// The largest possible range is year 1600 to year 3000
+//
+// By default, extended date support is only enabled for machines using 64 bit pointers,
+// but it can be enabled by specific ports
+#ifndef MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+#if MP_SSIZE_MAX > 2147483647
+#define MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE (1)
+#else
+#define MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE (0)
+#endif
+#endif
+
+// When support for dates <1970 is enabled, supporting >=2100 does not cost anything
+#ifndef MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND
+#define MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND (MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE)
+#endif
+
+// The type to be used to represent platform-specific timestamps depends on the choices above
+#define MICROPY_TIMESTAMP_IMPL_LONG_LONG (0)
+#define MICROPY_TIMESTAMP_IMPL_UINT (1)
+#define MICROPY_TIMESTAMP_IMPL_TIME_T (2)
+
+#ifndef MICROPY_TIMESTAMP_IMPL
+#if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE || MICROPY_EPOCH_IS_2000
+#define MICROPY_TIMESTAMP_IMPL (MICROPY_TIMESTAMP_IMPL_LONG_LONG)
+#else
+#define MICROPY_TIMESTAMP_IMPL (MICROPY_TIMESTAMP_IMPL_UINT)
+#endif
+#endif
+
+// `mp_timestamp_t` is the type that should be used by the port
+// to represent timestamps, and is referenced to the platform epoch
+#if MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_LONG_LONG
+typedef long long mp_timestamp_t;
+#elif MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_UINT
+typedef mp_uint_t mp_timestamp_t;
+#elif MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_TIME_T
+typedef time_t mp_timestamp_t;
+#endif
+
 // Whether POSIX-semantics non-blocking streams are supported
 #ifndef MICROPY_STREAMS_NON_BLOCK
 #define MICROPY_STREAMS_NON_BLOCK (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)