Computer Craft URL helper lib

local strlib = {}
strlib.findpattern = function( haystack, seed, start )
  return string.sub(haystack, string.find(haystack, seed, start))
end

strlib.explode = function(haystack, seed)
  if seed == '' then return haystack end
  local pos, arr = 0, {}
  for st, sp in function() return string.find(haystack,seed,pos,true) end do
    arr[#arr+1] = string.sub(haystack,pos,st-1)
    pos = sp+1
  end
  arr[#arr+1] = string.sub(haystack,pos)
  return arr
end

local hex = {"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"}
local hex2dec = {}
for k, v in pairs(hex) do
  hex2dec[v] = k-1
end

strlib.urlencode = function(str)
  local out = ""
  local c = 1
  while c <= #str do
    local chr = string.sub(str,c,c)
    local val = string.byte(chr)
    if(val>=48 and val<=57) or
      (val>=65 and val<=90) or
      (val>=97 and val<=122) then
      out = out..chr
    else
      out = out.."%"..hex[1+math.floor(val/16)]
            ..hex[1+(val%16)]
    end
    c = c+1
  end
  return out
end

strlib.urldecode = function(str)
  local out = ""
  local c = 0
  while c <= #str do
    local chr = string.sub(str,c,c)
    if chr ~= "%" then
      out = out .. chr
    else
      if #str < c+2 then return out end
      local code1 = string.sub(str,c+1,c+1)
      local code2 = string.sub(str,c+2,c+2)

      out = out..string.char(hex2dec[code1]*16+hex2dec[code2])
      c = c+2
    end
    c=c+1
  end
  return out
end