From d96d015887e6fcbe1ca8defcec44cb794421785d Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg42.2a@gmail.com>
Date: Sat, 21 Sep 2013 13:31:56 +0200
Subject: sync with Context as of 2013-09-21

---
 lualibs-os.lua | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

(limited to 'lualibs-os.lua')

diff --git a/lualibs-os.lua b/lualibs-os.lua
index 8bfcf78..7f3fd7c 100644
--- a/lualibs-os.lua
+++ b/lualibs-os.lua
@@ -492,3 +492,60 @@ end
 -- print(os.which("inkscape"))
 -- print(os.which("gs.exe"))
 -- print(os.which("ps2pdf"))
+
+-- These are moved from core-con.lua (as I needed them elsewhere).
+
+local function isleapyear(year)
+    return (year % 400 == 0) or ((year % 100 ~= 0) and (year % 4 == 0))
+end
+
+os.isleapyear = isleapyear
+
+-- nicer:
+--
+-- local days = {
+--     [false] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
+--     [true]  = { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
+-- }
+--
+-- local function nofdays(year,month)
+--     return days[isleapyear(year)][month]
+--     return month == 2 and isleapyear(year) and 29 or days[month]
+-- end
+--
+-- more efficient:
+
+local days = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
+
+local function nofdays(year,month)
+    if not month then
+        return isleapyear(year) and 365 or 364
+    else
+        return month == 2 and isleapyear(year) and 29 or days[month]
+    end
+end
+
+os.nofdays = nofdays
+
+function os.weekday(day,month,year)
+    return date("%w",time { year = year, month = month, day = day }) + 1
+end
+
+function os.validdate(year,month,day)
+    -- we assume that all three values are set
+    -- year is always ok, even if lua has a 1970 time limit
+    if month < 1 then
+        month = 1
+    elseif month > 12 then
+        month = 12
+    end
+    if day < 1 then
+        day = 1
+    else
+        local max = nofdays(year,month)
+        if day > max then
+            day = max
+        end
+    end
+    return year, month, day
+end
-- 
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