All patches and comments are welcome. Please squash your changes to logical
commits before using git-format-patch and git-send-email to
patches@git.madduck.net.
If you'd read over the Git project's submission guidelines and adhered to them,
I'd be especially grateful.
1 local strftime = require "luatz.strftime".strftime
2 local strformat = string.format
3 local floor = math.floor
4 local function idiv ( n , d )
9 local mon_lengths = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
10 -- Number of days in year until start of month; not corrected for leap years
11 local months_to_days_cumulative = { 0 }
13 months_to_days_cumulative [ i ] = months_to_days_cumulative [ i-1 ] + mon_lengths [ i-1 ]
15 -- For Sakamoto's Algorithm (day of week)
16 local sakamoto = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
18 local function is_leap ( y )
19 return (y % 4) == 0 and (y % 100) ~= 0 or (y % 400) == 0
22 local function year_length ( y )
23 return is_leap ( y ) and 366 or 365
26 local function month_length ( m , y )
28 return is_leap ( y ) and 29 or 28
30 return mon_lengths [ m ]
34 local function leap_years_since ( year )
35 return idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 )
38 local function day_of_year ( day , month , year )
39 local yday = months_to_days_cumulative [ month ]
40 if month > 2 and is_leap ( year ) then
46 local function day_of_week ( day , month , year )
50 return ( year + leap_years_since ( year ) + sakamoto[month] + day ) % 7 + 1
53 local function increment ( tens , units , base )
55 tens = tens + idiv ( units , base )
58 tens = tens - 1 + idiv ( -units , base )
59 units = base - ( -units % base )
64 -- Modify parameters so they all fit within the "normal" range
65 local function normalise ( year , month , day , hour , min , sec )
66 min , sec = increment ( min , sec , 60 ) -- TODO: consider leap seconds?
67 hour , min = increment ( hour , min , 60 )
68 day , hour = increment ( day , hour , 24 )
72 day = day + year_length ( year )
75 -- Lua months start from 1, need -1 and +1 around this increment
77 year , month = increment ( year , month , 12 )
80 -- This could potentially be slow if `day` is very large
82 local i = month_length ( month , year )
83 if day <= i then break end
92 return year , month , day , hour , min , sec
95 local leap_years_since_1970 = leap_years_since ( 1970 )
96 local function timestamp ( year , month , day , hour , min , sec )
97 year , month , day , hour , min , sec = normalise ( year , month , day , hour , min , sec )
99 local days_since_epoch = day_of_year ( day , month , year )
100 + 365 * ( year - 1970 )
101 -- Each leap year adds one day
102 + ( leap_years_since ( year - 1 ) - leap_years_since_1970 ) - 1
104 return days_since_epoch * (60*60*24)
111 local timetable_methods = { }
113 function timetable_methods:unpack ( )
114 return assert ( self.year , "year required" ) ,
115 assert ( self.month , "month required" ) ,
116 assert ( self.day , "day required" ) ,
124 function timetable_methods:normalise ( )
125 local year , month , day
126 year , month , day , self.hour , self.min , self.sec = normalise ( self:unpack ( ) )
131 self.yday = day_of_year ( day , month , year )
132 self.wday = day_of_week ( day , month , year )
136 timetable_methods.normalize = timetable_methods.normalise -- American English
138 function timetable_methods:timestamp ( )
139 return timestamp ( self:unpack ( ) )
142 function timetable_methods:rfc_3339 ( )
143 -- %06.3f gives 3 (=6-3) digits after decimal
144 return strformat ( "%04u-%02u-%02uT%02u:%02u:%06.3f" , self:unpack ( ) )
147 function timetable_methods:strftime ( format_string )
148 return strftime ( format_string , self )
151 local timetable_mt = {
152 __index = timetable_methods ;
153 __tostring = timetable_methods.rfc_3339 ;
154 __eq = function ( a , b )
155 return a:timestamp ( ) == b:timestamp ( )
157 __lt = function ( a , b )
158 return a:timestamp ( ) < b:timestamp ( )
162 local function cast_timetable ( tm )
163 return setmetatable ( tm , timetable_mt )
166 local function new_timetable ( year , month , day , hour , min , sec , yday , wday )
167 return cast_timetable {
179 function timetable_methods:clone ( )
180 return new_timetable ( self:unpack ( ) )
183 local function new_from_timestamp ( ts )
184 return new_timetable ( 1970 , 1 , 1 , 0 , 0 , ts )
188 day_of_year = day_of_year ;
189 day_of_week = day_of_week ;
190 normalise = normalise ;
191 timestamp = timestamp ;
193 new = new_timetable ;
194 new_from_timestamp = new_from_timestamp ;
195 cast = cast_timetable ;
196 timetable_mt = timetable_mt ;