Put the macros for compile-time computing of MJD for the start/end of…

… a month into a new 'mjd_defs.h' file, and modified them slightly to work with 32-bit longs (not just 64-bit ones).

delta_t.cpp

@@ -24,6 +24,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 #include <assert.h>
 #include "watdefs.h"
 #include "afuncs.h"
+#include "mjd_defs.h"
 
 #ifdef __WATCOMC__
 #define sinl(x) ((long double)sin((double)x))
@@ -363,29 +364,6 @@ long double DLL_FUNC tdb_minus_tdt( const long double t_centuries)
    return( rval);     /* difference is in _seconds_  */
 }
 
-/* These macros determine the MJD of the given date in 'YEAR'. They
-are valid for (Gregorian) years after roughly 20 billion years ago.
-This was chosen to comfortably include all dates since the Big Bang.
-We use the fact that February 1 is always 31 days after January 1,
-but have to work backward from January 1 of the following year to
-get March to December without having to consider leap days. */
-
-#define BASE_YEAR 19999999999L
-#define JAN_1( YEAR) (((YEAR) * 365L + ((YEAR) + BASE_YEAR) / 4L - ((YEAR) + BASE_YEAR) / 100L \
-                         + ((YEAR) + BASE_YEAR) / 400L) - 678940L \
-                         - ((BASE_YEAR + 1L) / 400L) * 97L)
-#define FEB_1( YEAR) (JAN_1( YEAR) + 31)
-#define DEC_1( YEAR) (JAN_1( (YEAR)+1) - 31)
-#define NOV_1( YEAR) (DEC_1( YEAR) - 30)
-#define OCT_1( YEAR) (NOV_1( YEAR) - 31)
-#define SEP_1( YEAR) (OCT_1( YEAR) - 30)
-#define AUG_1( YEAR) (SEP_1( YEAR) - 31)
-#define JUL_1( YEAR) (AUG_1( YEAR) - 31)
-#define JUN_1( YEAR) (JUL_1( YEAR) - 30)
-#define MAY_1( YEAR) (JUN_1( YEAR) - 31)
-#define APR_1( YEAR) (MAY_1( YEAR) - 30)
-#define MAR_1( YEAR) (APR_1( YEAR) - 31)
-
 #define utc0  (JAN_1( 1972))
       /*  'utc0' = MJD of date when the UTC leap seconds began */
 

mjd_defs.h

@@ -0,0 +1,40 @@
+#ifndef MJD_DEFS_H
+#define MJD_DEFS_H
+
+#include <stdint.h>
+#include <limits.h>
+
+/* These macros determine the MJD of the start of a month in the given
+'YEAR' at compile time.  If sizeof( long) == 8,  they are valid for
+(Gregorian) years after roughly 20 billion years ago. This was chosen
+to comfortably include all dates since the Big Bang.  If sizeof( long)
+== 4,  they only work between years -5877630 and +5881469;  beyond
+that,  the result overflows the 32-bit long.
+
+   February 1 will always be 31 days after January 1.  March 1 through
+December 1 will always be a fixed number of days before January 1 of
+the following year.   */
+
+#if LONG_MAX == INT64_MAX
+   #define BASE_YEAR 19999999999L
+#elif LONG_MAX == INT32_MAX
+   #define BASE_YEAR 1999999999L
+#else
+   #error "Long integers have an unrecognized size"
+#endif
+#define JAN_1( YEAR) (((YEAR) * 365L + ((YEAR) + BASE_YEAR) / 4L - ((YEAR) + BASE_YEAR) / 100L \
+                         + ((YEAR) + BASE_YEAR) / 400L) - 678940L \
+                         - ((BASE_YEAR + 1L) / 400L) * 97L)
+#define FEB_1( YEAR) (JAN_1( YEAR) + 31)
+#define DEC_1( YEAR) (JAN_1( (YEAR)+1) - 31)
+#define NOV_1( YEAR) (DEC_1( YEAR) - 30)
+#define OCT_1( YEAR) (NOV_1( YEAR) - 31)
+#define SEP_1( YEAR) (OCT_1( YEAR) - 30)
+#define AUG_1( YEAR) (SEP_1( YEAR) - 31)
+#define JUL_1( YEAR) (AUG_1( YEAR) - 31)
+#define JUN_1( YEAR) (JUL_1( YEAR) - 30)
+#define MAY_1( YEAR) (JUN_1( YEAR) - 31)
+#define APR_1( YEAR) (MAY_1( YEAR) - 30)
+#define MAR_1( YEAR) (APR_1( YEAR) - 31)
+
+#endif   /* #ifdef MJD_DEFS_H */

utc_test.cpp

@@ -15,32 +15,11 @@ along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 02110-1301, USA. */
 
-/* These macros determine the MJD of the given date in 'YEAR'.
-They are explained a bit in comments in 'delta_t.cpp' (q.v.).
-We're only using the July and January ones (the months in which
-leap seconds occur).  Unused macros are commented out,  just to
-avoid nuisance compiler warnings.   */
-
-#define BASE_YEAR 19999999999L
-#define JAN_1( YEAR) (((YEAR) * 365L + ((YEAR) + BASE_YEAR) / 4L - ((YEAR) + BASE_YEAR) / 100L \
-                         + ((YEAR) + BASE_YEAR) / 400L) - 678940L \
-                         - ((BASE_YEAR + 1L) / 400L) * 97L)
-// #define FEB_1( YEAR) (JAN_1( YEAR) + 31)
-#define DEC_1( YEAR) (JAN_1( (YEAR)+1) - 31)
-#define NOV_1( YEAR) (DEC_1( YEAR) - 30)
-#define OCT_1( YEAR) (NOV_1( YEAR) - 31)
-#define SEP_1( YEAR) (OCT_1( YEAR) - 30)
-#define AUG_1( YEAR) (SEP_1( YEAR) - 31)
-#define JUL_1( YEAR) (AUG_1( YEAR) - 31)
-// #define JUN_1( YEAR) (JUL_1( YEAR) - 30)
-// #define MAY_1( YEAR) (JUN_1( YEAR) - 31)
-// #define APR_1( YEAR) (MAY_1( YEAR) - 30)
-// #define MAR_1( YEAR) (APR_1( YEAR) - 31)
-
 #include <stdio.h>
 #include <stdlib.h>
 #include "watdefs.h"
 #include "afuncs.h"
+#include "mjd_defs.h"
 
 int main( const int argc, const char **argv)
 {