hex.lua

--[[---------------
Hex v0.4
-------------------
Hex conversion lib for lua.

How to use:
 hex.to_hex(n) -- convert a number to a hex string
 hex.to_dec(hex) -- convert a hex string(prefix with '0x' or '0X') to number
 
Part of LuaBit(http://luaforge.net/projects/bit/).

Under the MIT license.

copyright(c) 2006~2007 hanzhao (abrash_han@hotmail.com)
--]]---------------

local function to_hex(n)
   if (type(n) ~= "number") then
      error("non-number type passed in.")
   end

   -- checking not float
   if (n - math.floor(n) > 0) then
      error("trying to apply bitwise operation on non-integer!")
   end

   if (n < 0) then
      -- negative
      n = bit.tobits(bit.bnot(math.abs(n)) + 1)
      n = bit.tonumb(n)
   end

   hex_tbl = {'A', 'B', 'C', 'D', 'E', 'F'}
   hex_str = ""

   while (n ~= 0) do
      last = math.mod(n, 16)
      if (last < 10) then
         hex_str = tostring(last) .. hex_str
      else
         hex_str = hex_tbl[last-10+1] .. hex_str
      end
      n = math.floor(n/16)
   end
   if (hex_str == "") then
      hex_str = "0"
   end
   return "0x" .. hex_str
end

local function to_dec(hex)
   if (type(hex) ~= "string") then
      error("non-string type passed in.")
   end

   head = string.sub(hex, 1, 2)

   if (head ~= "0x" and head ~= "0X") then
      error("wrong hex format, should lead by 0x or 0X.")
   end

   v = tonumber(string.sub(hex, 3), 16)
   return v;
end

--------------------
-- hex lib interface
return {
   to_dec = to_dec,
   to_hex = to_hex
}

--[[
-- test
d = 4341688
h = to_hex(d)
print(h)
print(to_dec(h))


for i = 1, 100000 do
 h = hex.to_hex(i)
 d = hex.to_dec(h)
 if(d ~= i) then 
  error("failed " .. i .. ", " .. h)
 end
end
--]]