X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/d431ae6abaf5b0814389f2adf6069915d2e983c2..ebcbc1838c17993801dc53fee28a21d05f92aacc:/luatz/timetable.lua diff --git a/luatz/timetable.lua b/luatz/timetable.lua index 8c44f2f..fc89fca 100644 --- a/luatz/timetable.lua +++ b/luatz/timetable.lua @@ -1,3 +1,4 @@ +local strftime = require "luatz.strftime".strftime local strformat = string.format local floor = math.floor local function idiv ( n , d ) @@ -11,9 +12,17 @@ local months_to_days_cumulative = { 0 } for i = 2, 12 do months_to_days_cumulative [ i ] = months_to_days_cumulative [ i-1 ] + mon_lengths [ i-1 ] end +-- For Sakamoto's Algorithm (day of week) +local sakamoto = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4}; local function is_leap ( y ) - return (y % 4) == 0 and (y % 100) ~= 0 or (y % 400) == 0 + if (y % 4) ~= 0 then + return false + elseif (y % 100) ~= 0 then + return true + else + return (y % 400) == 0 + end end local function year_length ( y ) @@ -32,19 +41,6 @@ local function leap_years_since ( year ) return idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 ) end -local function doomsday ( year ) - return ( 3 -- Tuesday - - 1 + year + leap_years_since ( year ) ) - % 7 + 1 -end -local doomsday_cache = setmetatable ( { } , { - __index = function ( cache , year ) - local d = doomsday ( year ) - cache [ year ] = d - return d - end ; -} ) - local function day_of_year ( day , month , year ) local yday = months_to_days_cumulative [ month ] if month > 2 and is_leap ( year ) then @@ -53,11 +49,21 @@ local function day_of_year ( day , month , year ) return yday + day end -local function day_of_week ( yday , year ) - return ( yday - doomsday_cache [ year ] - 1 ) % 7 + 1 +local function day_of_week ( day , month , year ) + if month < 3 then + year = year - 1 + end + return ( year + leap_years_since ( year ) + sakamoto[month] + day ) % 7 + 1 +end + +local function borrow ( tens , units , base ) + local frac = tens % 1 + units = units + frac * base + tens = tens - frac + return tens , units end -local function increment ( tens , units , base ) +local function carry ( tens , units , base ) if units >= base then tens = tens + idiv ( units , base ) units = units % base @@ -70,32 +76,50 @@ end -- Modify parameters so they all fit within the "normal" range local function normalise ( year , month , day , hour , min , sec ) - min , sec = increment ( min , sec , 60 ) -- TODO: consider leap seconds? - hour , min = increment ( hour , min , 60 ) - day , hour = increment ( day , hour , 24 ) - - while day <= 0 do + -- `month` and `day` start from 1, need -1 and +1 so it works modulo + month , day = month - 1 , day - 1 + + -- Convert everything (except seconds) to an integer + -- by propagating fractional components down. + year , month = borrow ( year , month , 12 ) + -- Carry from month to year first, so we get month length correct in next line around leap years + year , month = carry ( year , month , 12 ) + month , day = borrow ( month , day , month_length ( floor ( month + 1 ) , year ) ) + day , hour = borrow ( day , hour , 24 ) + hour , min = borrow ( hour , min , 60 ) + min , sec = borrow ( min , sec , 60 ) + + -- Propagate out of range values up + -- e.g. if `min` is 70, `hour` increments by 1 and `min` becomes 10 + -- This has to happen for all columns after borrowing, as lower radixes may be pushed out of range + min , sec = carry ( min , sec , 60 ) -- TODO: consider leap seconds? + hour , min = carry ( hour , min , 60 ) + day , hour = carry ( day , hour , 24 ) + -- Ensure `day` is not underflowed + -- Add a whole year of days at a time, this is later resolved by adding months + -- TODO[OPTIMIZE]: This could be slow if `day` is far out of range + while day < 0 do year = year - 1 day = day + year_length ( year ) end + year , month = carry ( year , month , 12 ) - -- Lua months start from 1, need -1 and +1 around this increment - month = month - 1 - year , month = increment ( year , month , 12 ) - month = month + 1 - - -- This could potentially be slow if `day` is very large + -- TODO[OPTIMIZE]: This could potentially be slow if `day` is very large while true do - local i = month_length ( month , year ) - if day <= i then break end + local i = month_length ( month + 1 , year ) + if day < i then break end day = day - i month = month + 1 - if month > 12 then - month = 1 + if month >= 12 then + month = 0 year = year + 1 end end + -- Now we can place `day` and `month` back in their normal ranges + -- e.g. month as 1-12 instead of 0-11 + month , day = month + 1 , day + 1 + return year , month , day , hour , min , sec end @@ -135,12 +159,8 @@ function timetable_methods:normalise ( ) self.day = day self.month = month self.year = year - - local yday = day_of_year ( day , month , year ) - local wday = day_of_week ( yday , year ) - - self.yday = yday - self.wday = wday + self.yday = day_of_year ( day , month , year ) + self.wday = day_of_week ( day , month , year ) return self end @@ -155,6 +175,10 @@ function timetable_methods:rfc_3339 ( ) return strformat ( "%04u-%02u-%02uT%02u:%02u:%06.3f" , self:unpack ( ) ) end +function timetable_methods:strftime ( format_string ) + return strftime ( format_string , self ) +end + local timetable_mt local function coerce_arg ( t ) @@ -168,10 +192,13 @@ timetable_mt = { __index = timetable_methods ; __tostring = timetable_methods.rfc_3339 ; __eq = function ( a , b ) - return coerce_arg ( a ) == coerce_arg ( b ) + return a:timestamp ( ) == b:timestamp ( ) end ; __lt = function ( a , b ) - return coerce_arg ( a ) < coerce_arg ( b ) + return a:timestamp ( ) < b:timestamp ( ) + end ; + __sub = function ( a , b ) + return coerce_arg ( a ) - coerce_arg ( b ) end ; } @@ -197,11 +224,16 @@ function timetable_methods:clone ( ) end local function new_from_timestamp ( ts ) - return new_timetable ( 1970 , 1 , 1 , 0 , 0 , ts ) + if type ( ts ) ~= "number" then + error ( "bad argument #1 to 'new_from_timestamp' (number expected, got " .. type ( ts ) .. ")" , 2 ) + end + return new_timetable ( 1970 , 1 , 1 , 0 , 0 , ts ):normalise ( ) end return { - doomsday = doomsday ; + is_leap = is_leap ; + day_of_year = day_of_year ; + day_of_week = day_of_week ; normalise = normalise ; timestamp = timestamp ;