if not modules then modules = { } end modules ['l-md5'] = {
    version   = 1.001,
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- This also provides file checksums and checkers.

local md5, file = md5, file
local gsub, format, byte = string.gsub, string.format, string.byte

local function convert(str,fmt)
    return (gsub(md5.sum(str),".",function(chr) return format(fmt,byte(chr)) end))
end

if not md5.HEX then function md5.HEX(str) return convert(str,"%02X") end end
if not md5.hex then function md5.hex(str) return convert(str,"%02x") end end
if not md5.dec then function md5.dec(str) return convert(str,"%03i") end end

--~ if not md5.HEX then
--~     local function remap(chr) return format("%02X",byte(chr)) end
--~     function md5.HEX(str) return (gsub(md5.sum(str),".",remap)) end
--~ end
--~ if not md5.hex then
--~     local function remap(chr) return format("%02x",byte(chr)) end
--~     function md5.hex(str) return (gsub(md5.sum(str),".",remap)) end
--~ end
--~ if not md5.dec then
--~     local function remap(chr) return format("%03i",byte(chr)) end
--~     function md5.dec(str) return (gsub(md5.sum(str),".",remap)) end
--~ end

function file.needsupdating(oldname,newname,threshold) -- size modification access change
    local oldtime = lfs.attributes(oldname,"modification")
    if oldtime then
        local newtime = lfs.attributes(newname,"modification")
        if not newtime then
            return true -- no new file, so no updating needed
        elseif newtime >= oldtime then
            return false -- new file definitely needs updating
        elseif oldtime - newtime < (threshold or 1) then
            return false -- new file is probably still okay
        else
            return true -- new file has to be updated
        end
    else
        return false -- no old file, so no updating needed
    end
end

file.needs_updating = file.needsupdating

function file.syncmtimes(oldname,newname)
    local oldtime = lfs.attributes(oldname,"modification")
    if oldtime and lfs.isfile(newname) then
        lfs.touch(newname,oldtime,oldtime)
    end
end

function file.checksum(name)
    if md5 then
        local data = io.loaddata(name)
        if data then
            return md5.HEX(data)
        end
    end
    return nil
end

function file.loadchecksum(name)
    if md5 then
        local data = io.loaddata(name .. ".md5")
        return data and (gsub(data,"%s",""))
    end
    return nil
end

function file.savechecksum(name,checksum)
    if not checksum then checksum = file.checksum(name) end
    if checksum then
        io.savedata(name .. ".md5",checksum)
        return checksum
    end
    return nil
end