Anybody have some unicode string handling code I could use?

Question

Text handling plugins are not working for some users, since Lua and Lr are not on the same page char-representation-wise.
For example, if you enter
À
in Lightroom, it's getting interpreted as
À
in Lua.
in non-plugin environment, one could just use slnunicode, however in plugin one needs pure lua solution.
Anybody?
ref: http://lua-users.org/wiki/LuaUnicode
R

Answer 1

Try
Debug.pause( "uni-find", string.find( photo:getFormattedMetadata( 'title' ), 'À' ) )
when title field has an 'À' in it.
Instead of seeing the coordinates of the 'À' that is there, you'll see nil.
PS - this code looks promising (?) found at http://forums.gaspowered.com/viewtopic.php?f=19&t=29879
   function conv2utf8(unicode_list)
      local result = ''
      local w,x,y,z = 0,0,0,0
      local function modulo(a, b)
         return a - math.floor(a/b) * b
      end
      for i,v in ipairs(unicode_list) do
         if v ~= 0 and v ~= nil then
            if v <= 0x7F then -- same as ASCII
               result = result .. string.char(v)
            elseif v >= 0x80 and v <= 0x7FF then -- 2 bytes
               y = (v & 0x0007C0) >> 6
               z = v & 0x00003F
               y = math.floor(modulo(v, 0x000800) / 64)
               z = modulo(v, 0x000040)
               result = result .. string.char(0xC0 + y, 0x80 + z)
            elseif (v >= 0x800 and v <= 0xD7FF) or (v >= 0xE000 and v <= 0xFFFF) then -- 3 bytes
               x = (v & 0x00F000) >> 12
               y = (v & 0x000FC0) >> 6
               z = v & 0x00003F
               x = math.floor(modulo(v, 0x010000) / 4096)
               y = math.floor(modulo(v, 0x001000) / 64)
               z = modulo(v, 0x000040)
               result = result .. string.char(0xE0 + x, 0x80 + y, 0x80 + z)
            elseif (v >= 0x10000 and v <= 0x10FFFF) then -- 4 bytes
               w = (v & 0x1C0000) >> 18
               x = (v & 0x03F000) >> 12
               y = (v & 0x000FC0) >> 6
               z = v & 0x00003F
               w = math.floor(modulo(v, 0x200000) / 262144)
               x = math.floor(modulo(v, 0x040000) / 4096)
               y = math.floor(modulo(v, 0x001000) / 64)
               z = modulo(v, 0x000040)
               result = result .. string.char(0xF0 + w, 0x80 + x, 0x80 + y, 0x80 + z)
            end
         end
      end
      return result
   end
or maybe this: (?)
function unichr(ord)
    if ord == nil then return nil end
    if ord < 32 then return string.format('\\x%02x', ord) end
    if ord < 126 then return string.char(ord) end
    if ord < 65539 then return string.format("\\u%04x", ord) end
    if ord < 1114111 then return string.format("\\u%08x", ord) end
end
from http://stackoverflow.com/questions/7780179/what-is-the-way-to-represent-a-unichar-in-lua
R