------------------------------------------------------------------------------ | |

-- -- | |

-- GNAT RUN-TIME COMPONENTS -- | |

-- -- | |

-- A D A . C A L E N D A R -- | |

-- -- | |

-- S p e c -- | |

-- -- | |

-- Copyright (C) 1992-2021, Free Software Foundation, Inc. -- | |

-- -- | |

-- This specification is derived from the Ada Reference Manual for use with -- | |

-- GNAT. The copyright notice above, and the license provisions that follow -- | |

-- apply solely to the contents of the part following the private keyword. -- | |

-- -- | |

-- GNAT is free software; you can redistribute it and/or modify it under -- | |

-- terms of the GNU General Public License as published by the Free Soft- -- | |

-- ware Foundation; either version 3, or (at your option) any later ver- -- | |

-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- | |

-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- | |

-- or FITNESS FOR A PARTICULAR PURPOSE. -- | |

-- -- | |

-- As a special exception under Section 7 of GPL version 3, you are granted -- | |

-- additional permissions described in the GCC Runtime Library Exception, -- | |

-- version 3.1, as published by the Free Software Foundation. -- | |

-- -- | |

-- You should have received a copy of the GNU General Public License and -- | |

-- a copy of the GCC Runtime Library Exception along with this program; -- | |

-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- | |

-- <http://www.gnu.org/licenses/>. -- | |

-- -- | |

-- GNAT was originally developed by the GNAT team at New York University. -- | |

-- Extensive contributions were provided by Ada Core Technologies Inc. -- | |

-- -- | |

------------------------------------------------------------------------------ | |

package Ada.Calendar with | |

SPARK_Mode, | |

Abstract_State => (Clock_Time with Synchronous), | |

Initializes => Clock_Time | |

is | |

type Time is private; | |

-- Declarations representing limits of allowed local time values. Note that | |

-- these do NOT constrain the possible stored values of time which may well | |

-- permit a larger range of times (this is explicitly allowed in Ada 95). | |

subtype Year_Number is Integer range 1901 .. 2399; | |

subtype Month_Number is Integer range 1 .. 12; | |

subtype Day_Number is Integer range 1 .. 31; | |

-- A Day_Duration value of 86_400.0 designates a new day | |

subtype Day_Duration is Duration range 0.0 .. 86_400.0; | |

function Clock return Time with | |

Volatile_Function, | |

Global => Clock_Time; | |

-- The returned time value is the number of nanoseconds since the start | |

-- of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled, | |

-- the result will contain all elapsed leap seconds since the start of | |

-- Ada time until now. | |

function Year (Date : Time) return Year_Number; | |

function Month (Date : Time) return Month_Number; | |

function Day (Date : Time) return Day_Number; | |

function Seconds (Date : Time) return Day_Duration; | |

-- SPARK Note: These routines, just like Split and Time_Of below, might use | |

-- the OS-specific timezone database that is typically stored in a file. | |

-- This side effect needs to be modeled, so there is no Global => null. | |

procedure Split | |

(Date : Time; | |

Year : out Year_Number; | |

Month : out Month_Number; | |

Day : out Day_Number; | |

Seconds : out Day_Duration); | |

-- Break down a time value into its date components set in the current | |

-- time zone. If Split is called on a time value created using Ada 2005 | |

-- Time_Of in some arbitrary time zone, the input value will always be | |

-- interpreted as relative to the local time zone. | |

function Time_Of | |

(Year : Year_Number; | |

Month : Month_Number; | |

Day : Day_Number; | |

Seconds : Day_Duration := 0.0) return Time; | |

-- GNAT Note: Normally when procedure Split is called on a Time value | |

-- result of a call to function Time_Of, the out parameters of procedure | |

-- Split are identical to the in parameters of function Time_Of. However, | |

-- when a non-existent time of day is specified, the values for Seconds | |

-- may or may not be different. This may happen when Daylight Saving Time | |

-- (DST) is in effect, on the day when switching to DST, if Seconds | |

-- specifies a time of day in the hour that does not exist. For example, | |

-- in New York: | |

-- | |

-- Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0) | |

-- | |

-- will return a Time value T. If Split is called on T, the resulting | |

-- Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being | |

-- a time that not exist). | |

function "+" (Left : Time; Right : Duration) return Time | |

with | |

Global => null; | |

function "+" (Left : Duration; Right : Time) return Time | |

with | |

Global => null; | |

function "-" (Left : Time; Right : Duration) return Time | |

with | |

Global => null; | |

function "-" (Left : Time; Right : Time) return Duration | |

with | |

Global => null; | |

-- The first three functions will raise Time_Error if the resulting time | |

-- value is less than the start of Ada time in UTC or greater than the | |

-- end of Ada time in UTC. The last function will raise Time_Error if the | |

-- resulting difference cannot fit into a duration value. | |

function "<" (Left, Right : Time) return Boolean with Global => null; | |

function "<=" (Left, Right : Time) return Boolean with Global => null; | |

function ">" (Left, Right : Time) return Boolean with Global => null; | |

function ">=" (Left, Right : Time) return Boolean with Global => null; | |

Time_Error : exception; | |

private | |

-- Mark the private part as SPARK_Mode Off to avoid accounting for variable | |

-- Invalid_Time_Zone_Offset in abstract state. | |

pragma SPARK_Mode (Off); | |

pragma Inline (Clock); | |

pragma Inline (Year); | |

pragma Inline (Month); | |

pragma Inline (Day); | |

pragma Inline ("+"); | |

pragma Inline ("-"); | |

pragma Inline ("<"); | |

pragma Inline ("<="); | |

pragma Inline (">"); | |

pragma Inline (">="); | |

-- The units used in this version of Ada.Calendar are nanoseconds. The | |

-- following constants provide values used in conversions of seconds or | |

-- days to the underlying units. | |

Nano : constant := 1_000_000_000; | |

Nano_F : constant := 1_000_000_000.0; | |

Nanos_In_Day : constant := 86_400_000_000_000; | |

Secs_In_Day : constant := 86_400; | |

---------------------------- | |

-- Implementation of Time -- | |

---------------------------- | |

-- Time is represented as a signed 64 bit signed integer count of | |

-- nanoseconds since the "epoch" 2150-01-01 00:00:00 UTC. Thus a value of 0 | |

-- represents the epoch. As of this writing, the epoch is in the future, | |

-- so Time values returned by Clock will be negative. | |

-- | |

-- Time values produced by Time_Of are internally normalized to UTC | |

-- regardless of their local time zone. This representation ensures correct | |

-- handling of leap seconds as well as performing arithmetic. In Ada 95, | |

-- Split and Time_Of will treat a time value as being in the local time | |

-- zone, in Ada 2005, Split and Time_Of will treat a time value as being in | |

-- the designated time zone by the formal parameter or in UTC by | |

-- default. The size of the type is large enough to cover the Ada | |

-- range of time (1901-01-01T00:00:00.0 UTC - 2399-12-31T23:59:59.999999999 | |

-- UTC). | |

------------------ | |

-- Leap Seconds -- | |

------------------ | |

-- Due to Earth's slowdown, the astronomical time is not as precise as the | |

-- International Atomic Time. To compensate for this inaccuracy, a single | |

-- leap second is added after the last day of June or December. The count | |

-- of seconds during those occurrences becomes: | |

-- ... 58, 59, leap second 60, 0, 1, 2 ... | |

-- Unlike leap days, leap seconds occur simultaneously around the world. | |

-- In other words, if a leap second occurs at 23:59:60 UTC, it also occurs | |

-- on 18:59:60 -5 the same day or 2:59:60 +2 on the next day. | |

-- Leap seconds do not follow a formula. The International Earth Rotation | |

-- and Reference System Service decides when to add one. Leap seconds are | |

-- included in the representation of time in Ada 95 mode. As a result, | |

-- the following two time values will differ by two seconds: | |

-- 1972-06-30 23:59:59.0 | |

-- 1972-07-01 00:00:00.0 | |

-- When a new leap second is introduced, the following steps must be | |

-- carried out: | |

-- 1) Increment Leap_Seconds_Count in a-calend.adb by one | |

-- 2) Increment LS_Count in xleaps.adb by one | |

-- 3) Add the new date to the aggregate of array LS_Dates in | |

-- xleaps.adb | |

-- 4) Compile and execute xleaps | |

-- 5) Replace the values of Leap_Second_Times in a-calend.adb with the | |

-- aggregate generated by xleaps | |

-- The algorithms that build the actual leap second values and discover | |

-- how many leap seconds have occurred between two dates do not need any | |

-- modification. | |

------------------------------ | |

-- Non-leap Centennial Years -- | |

------------------------------ | |

-- Over the range of Ada time, centennial years 2100, 2200 and 2300 are | |

-- non-leap. As a consequence, seven non-leap years occur over the period | |

-- of year - 4 to year + 4. Internally, routines Split and Time_Of add or | |

-- subtract a "fake" February 29 to facilitate the arithmetic involved. | |

------------------------ | |

-- Local Declarations -- | |

------------------------ | |

type Time_Rep is new Long_Long_Integer; | |

type Time is new Time_Rep; | |

-- The underlying type of Time has been chosen to be a 64 bit signed | |

-- integer number since it allows for easier processing of sub-seconds | |

-- and arithmetic. We use Long_Long_Integer to allow this unit to compile | |

-- when using custom target configuration files where the max integer is | |

-- 32 bits. This is useful for static analysis tools such as SPARK or | |

-- CodePeer. | |

-- | |

-- Note: the reason we have two separate types here is to avoid problems | |

-- with overloading ambiguities in the body if we tried to use Time as an | |

-- internal computational type. | |

function Epoch_Offset return Time_Rep; | |

pragma Inline (Epoch_Offset); | |

-- Return the difference between our epoch and 1970-1-1 UTC (the Unix | |

-- epoch) expressed in nanoseconds. Note that year 2100 is non-leap. | |

Days_In_Month : constant array (Month_Number) of Day_Number := | |

(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); | |

-- Days in month for non-leap year, leap year case is adjusted in code | |

Invalid_Time_Zone_Offset : Long_Integer; | |

pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff"); | |

function Is_Leap (Year : Year_Number) return Boolean; | |

-- Determine whether a given year is leap | |

---------------------------------------------------------- | |

-- Target-Independent Interface to Children of Calendar -- | |

---------------------------------------------------------- | |

-- The following packages provide a target-independent interface to the | |

-- children of Calendar - Arithmetic, Conversions, Delays, Formatting and | |

-- Time_Zones. | |

--------------------------- | |

-- Arithmetic_Operations -- | |

--------------------------- | |

package Arithmetic_Operations is | |

function Add (Date : Time; Days : Long_Integer) return Time; | |

-- Add a certain number of days to a time value | |

procedure Difference | |

(Left : Time; | |

Right : Time; | |

Days : out Long_Integer; | |

Seconds : out Duration; | |

Leap_Seconds : out Integer); | |

-- Calculate the difference between two time values in terms of days, | |

-- seconds and leap seconds elapsed. The leap seconds are not included | |

-- in the seconds returned. If Left is greater than Right, the returned | |

-- values are positive, negative otherwise. | |

function Subtract (Date : Time; Days : Long_Integer) return Time; | |

-- Subtract a certain number of days from a time value | |

end Arithmetic_Operations; | |

--------------------------- | |

-- Conversion_Operations -- | |

--------------------------- | |

package Conversion_Operations is | |

function To_Ada_Time (Unix_Time : Long_Integer) return Time; | |

-- Unix to Ada Epoch conversion | |

function To_Ada_Time | |

(tm_year : Integer; | |

tm_mon : Integer; | |

tm_day : Integer; | |

tm_hour : Integer; | |

tm_min : Integer; | |

tm_sec : Integer; | |

tm_isdst : Integer) return Time; | |

-- Struct tm to Ada Epoch conversion | |

function To_Duration | |

(tv_sec : Long_Integer; | |

tv_nsec : Long_Integer) return Duration; | |

-- Struct timespec to Duration conversion | |

procedure To_Struct_Timespec | |

(D : Duration; | |

tv_sec : out Long_Integer; | |

tv_nsec : out Long_Integer); | |

-- Duration to struct timespec conversion | |

procedure To_Struct_Tm | |

(T : Time; | |

tm_year : out Integer; | |

tm_mon : out Integer; | |

tm_day : out Integer; | |

tm_hour : out Integer; | |

tm_min : out Integer; | |

tm_sec : out Integer); | |

-- Time to struct tm conversion | |

function To_Unix_Time (Ada_Time : Time) return Long_Integer; | |

-- Ada to Unix Epoch conversion | |

end Conversion_Operations; | |

---------------------- | |

-- Delay_Operations -- | |

---------------------- | |

package Delay_Operations is | |

function To_Duration (Date : Time) return Duration; | |

-- Given a time value in nanoseconds since 1901, convert it into a | |

-- duration value giving the number of nanoseconds since the Unix Epoch. | |

end Delay_Operations; | |

--------------------------- | |

-- Formatting_Operations -- | |

--------------------------- | |

package Formatting_Operations is | |

function Day_Of_Week (Date : Time) return Integer; | |

-- Determine which day of week Date falls on. The returned values are | |

-- within the range of 0 .. 6 (Monday .. Sunday). | |

procedure Split | |

(Date : Time; | |

Year : out Year_Number; | |

Month : out Month_Number; | |

Day : out Day_Number; | |

Day_Secs : out Day_Duration; | |

Hour : out Integer; | |

Minute : out Integer; | |

Second : out Integer; | |

Sub_Sec : out Duration; | |

Leap_Sec : out Boolean; | |

Use_TZ : Boolean; | |

Is_Historic : Boolean; | |

Time_Zone : Long_Integer); | |

pragma Export (Ada, Split, "__gnat_split"); | |

-- Split a time value into its components. If flag Is_Historic is set, | |

-- this routine would try to use to the best of the OS's abilities the | |

-- time zone offset that was or will be in effect on Date. Set Use_TZ | |

-- to use the local time zone (the value in Time_Zone is ignored) when | |

-- splitting a time value. | |

function Time_Of | |

(Year : Year_Number; | |

Month : Month_Number; | |

Day : Day_Number; | |

Day_Secs : Day_Duration; | |

Hour : Integer; | |

Minute : Integer; | |

Second : Integer; | |

Sub_Sec : Duration; | |

Leap_Sec : Boolean; | |

Use_Day_Secs : Boolean; | |

Use_TZ : Boolean; | |

Is_Historic : Boolean; | |

Time_Zone : Long_Integer) return Time; | |

pragma Export (Ada, Time_Of, "__gnat_time_of"); | |

-- Given all the components of a date, return the corresponding time | |

-- value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the | |

-- day duration will be calculated from Hour, Minute, Second and Sub_ | |

-- Sec. If flag Is_Historic is set, this routine would try to use to the | |

-- best of the OS's abilities the time zone offset that was or will be | |

-- in effect on the input date. Set Use_TZ to use the local time zone | |

-- (the value in formal Time_Zone is ignored) when building a time value | |

-- and to verify the validity of a requested leap second. | |

end Formatting_Operations; | |

--------------------------- | |

-- Time_Zones_Operations -- | |

--------------------------- | |

package Time_Zones_Operations is | |

function UTC_Time_Offset (Date : Time) return Long_Integer; | |

-- Return (in seconds) the difference between the local time zone and | |

-- UTC time at a specific historic date. | |

end Time_Zones_Operations; | |

end Ada.Calendar; |