score: Change TOD_LATEST_YEAR to 2099

This simplifies the implementation a bit.  Declare _TOD_Days_to_date[] in
<rtems/score/todimpl.h>.  Make _TOD_Days_per_month[] and
_TOD_Days_since_last_leap_year[] static.

Update #4338.

4 files changed, 47 insertions, 41 deletions

diff --git a/cpukit/include/rtems/score/todimpl.h b/cpukit/include/rtems/score/todimpl.h
index f85689fd9c..acfec00186 100644
--- a/cpukit/include/rtems/score/todimpl.h
+++ b/cpukit/include/rtems/score/todimpl.h
@@ -142,12 +142,16 @@ extern "C" {
  *  32 bits can accept as latest point in time 2106-Feb-7 6:28:15
  *  but to simplify the implementation, is was decided to only
  *  check that the year is not greater than the year of this constant.
+ *  The year 2099 was chosen because all years evenly divisible by 4 from 1988
+ *  to 2099 are leap years.  In this time frame, years evenly divisible by 100
+ *  are no leap years unless they are evenly divisible by 400.  Thus the year
+ *  2000 is a leap year.
  *
- *  The internal realtime clock can run centuries longer but in
+ *  The internal CLOCK_REALTIME can run centuries longer but in
  *  contrast to the POSIX API, the RTEMS Classic API does not
  *  support this for efficiency reasons.
  */
-#define TOD_LATEST_YEAR 2105
+#define TOD_LATEST_YEAR 2099
 
 /**
  * @addtogroup RTEMSScoreTOD
@@ -176,6 +180,14 @@ typedef struct {
 extern TOD_Control _TOD;
 
 /**
+ * @brief This array contains the number of days in all months up to the month
+ *   indicated by the index of the second dimension.
+ *
+ * The first dimension should be 0 for leap years, and 1 otherwise.
+ */
+extern const uint16_t _TOD_Days_to_date[ 2 ][ 13 ];
+
+/**
  * @brief Locks the time of day mutex.
  */
 void _TOD_Lock( void );
@@ -216,6 +228,21 @@ static inline void _TOD_Release( ISR_lock_Context *lock_context )
 }
 
 /**
+ * @brief Maps the year to the leap year index.
+ *
+ * @param year is the year to map.
+ *
+ * @retval 0 The year is a leap year.
+ *
+ * @retval 1 The year is not a leap year.
+ */
+static inline size_t _TOD_Get_leap_year_index( uint32_t year )
+{
+  _Assert( year % 4 != 0 || year % 100 != 0 || year % 400 == 0 );
+  return ( ( year % 4 ) + 3 ) / 4;
+}
+
+/**
  * @brief Checks the time point is a valid new time of day for _TOD_Set().
  *
  * @param tod the time of day to check.
diff --git a/cpukit/rtems/src/clockgettod.c b/cpukit/rtems/src/clockgettod.c
index dea136d477..5058b42375 100644
--- a/cpukit/rtems/src/clockgettod.c
+++ b/cpukit/rtems/src/clockgettod.c
@@ -32,8 +32,6 @@
 #define RTEMS_DAYS_PER_YEAR   (365UL)
 #define RTEMS_YEAR_BASE       (1970UL)
 
-extern const uint16_t _TOD_Days_to_date[2][13];
-
 static bool _Leap_year(
   uint32_t year
 )
@@ -64,9 +62,9 @@ static uint32_t _Year_day_as_month(
   uint32_t        month = 0;
 
   if ( _Leap_year( year ) )
-    days_to_date = _TOD_Days_to_date[1];
-  else
     days_to_date = _TOD_Days_to_date[0];
+  else
+    days_to_date = _TOD_Days_to_date[1];
 
   days_to_date += 2;
 
diff --git a/cpukit/rtems/src/clocktodtoseconds.c b/cpukit/rtems/src/clocktodtoseconds.c
index 86e89f86eb..43bf6c59c5 100644
--- a/cpukit/rtems/src/clocktodtoseconds.c
+++ b/cpukit/rtems/src/clocktodtoseconds.c
@@ -23,16 +23,9 @@
 #include <rtems/rtems/clockimpl.h>
 #include <rtems/score/todimpl.h>
 
-#define TOD_SECONDS_AT_2100_03_01_00_00 4107542400UL
-
-/*
- *  The following array contains the number of days in all months
- *  up to the month indicated by the index of the second dimension.
- *  The first dimension should be 1 for leap years, and 0 otherwise.
- */
-const uint16_t   _TOD_Days_to_date[2][13] = {
-  { 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 },
-  { 0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 }
+const uint16_t _TOD_Days_to_date[ 2 ][ 13 ] = {
+  { 0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 },
+  { 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 }
 };
 
 /*
@@ -48,21 +41,18 @@ Watchdog_Interval   _TOD_To_seconds(
   const rtems_time_of_day *the_tod
 )
 {
-  uint32_t   time;
-  uint32_t   year_mod_4;
+  uint32_t time;
+  size_t   leap_year_index;
 
   time = the_tod->day - 1;
-  year_mod_4 = the_tod->year & 3;
 
-  if ( year_mod_4 == 0 )
-    time += _TOD_Days_to_date[ 1 ][ the_tod->month ];
-  else
-    time += _TOD_Days_to_date[ 0 ][ the_tod->month ];
+  leap_year_index = _TOD_Get_leap_year_index( the_tod->year );
+  time += _TOD_Days_to_date[ leap_year_index ][ the_tod->month ];
 
   time += ( (the_tod->year - TOD_BASE_YEAR) / 4 ) *
             ( (TOD_DAYS_PER_YEAR * 4) + 1);
 
-  time += _TOD_Days_since_last_leap_year[ year_mod_4 ];
+  time += _TOD_Days_since_last_leap_year[ the_tod->year % 4 ];
 
   time *= TOD_SECONDS_PER_DAY;
 
@@ -70,13 +60,6 @@ Watchdog_Interval   _TOD_To_seconds(
              * TOD_SECONDS_PER_MINUTE;
 
   time += the_tod->second;
-
-  /* The year 2100 is not a leap year */
-  if ( time
-      >= (TOD_SECONDS_AT_2100_03_01_00_00 - TOD_SECONDS_1970_THROUGH_1988)) {
-    time -= TOD_SECONDS_PER_DAY;
-  }
-
   time += TOD_SECONDS_1970_THROUGH_1988;
 
   return( time );
diff --git a/cpukit/rtems/src/clocktodvalidate.c b/cpukit/rtems/src/clocktodvalidate.c
index 0e3b5772b5..4433374e65 100644
--- a/cpukit/rtems/src/clocktodvalidate.c
+++ b/cpukit/rtems/src/clocktodvalidate.c
@@ -26,13 +26,13 @@
 
 /*
  *  The following array contains the number of days in all months.
- *  The first dimension should be 1 for leap years, and 0 otherwise.
+ *  The first dimension should be 0 for leap years, and 1 otherwise.
  *  The second dimension should range from 1 to 12 for January to
- *  February, respectively.
+ *  December, respectively.
  */
-const uint32_t   _TOD_Days_per_month[ 2 ][ 13 ] = {
-  { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
-  { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
+static const uint32_t _TOD_Days_per_month[ 2 ][ 13 ] = {
+  { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
+  { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
 };
 
 rtems_status_code _TOD_Validate(
@@ -40,6 +40,7 @@ rtems_status_code _TOD_Validate(
   TOD_Ticks_validation     ticks_validation
 )
 {
+  size_t  leap_year_index;
   uint32_t days_in_month;
   uint32_t ticks_per_second;
   uint32_t ticks_mask;
@@ -79,11 +80,8 @@ rtems_status_code _TOD_Validate(
     return RTEMS_INVALID_CLOCK;
   }
 
-  if (((the_tod->year % 4) == 0 && (the_tod->year % 100 != 0)) ||
-     (the_tod->year % 400 == 0))
-    days_in_month = _TOD_Days_per_month[ 1 ][ the_tod->month ];
-  else
-    days_in_month = _TOD_Days_per_month[ 0 ][ the_tod->month ];
+  leap_year_index = _TOD_Get_leap_year_index( the_tod->year );
+  days_in_month = _TOD_Days_per_month[ leap_year_index ][ the_tod->month ];
 
   if ( the_tod->day > days_in_month ) {
     return RTEMS_INVALID_CLOCK;