function struct.pack()

in lib/shenyu/register/core/struct.lua [25:113]

• 79 lines of code
• 17 McCabe index (conditional complexity)

function struct.pack(format, ...)
  local stream = {}
  local vars = {...}
  local endianness = true

  for i = 1, format:len() do
    local opt = format:sub(i, i)

    if opt == "<" then
      endianness = true
    elseif opt == ">" then
      endianness = false
    elseif opt:find("[bBhHiIlL]") then
      local n = opt:find("[hH]") and 2 or opt:find("[iI]") and 4 or opt:find("[lL]") and 8 or 1
      local val = tonumber(table.remove(vars, 1))

      local bytes = {}
      for j = 1, n do
        table.insert(bytes, string.char(val % (2 ^ 8)))
        val = math.floor(val / (2 ^ 8))
      end

      if not endianness then
        table.insert(stream, string.reverse(table.concat(bytes)))
      else
        table.insert(stream, table.concat(bytes))
      end
    elseif opt:find("[fd]") then
      local val = tonumber(table.remove(vars, 1))
      local sign = 0

      if val < 0 then
        sign = 1
        val = -val
      end

      local mantissa, exponent = math.frexp(val)
      if val == 0 then
        mantissa = 0
        exponent = 0
      else
        mantissa = (mantissa * 2 - 1) * math.ldexp(0.5, (opt == "d") and 53 or 24)
        exponent = exponent + ((opt == "d") and 1022 or 126)
      end

      local bytes = {}
      if opt == "d" then
        val = mantissa
        for i = 1, 6 do
          table.insert(bytes, string.char(math.floor(val) % (2 ^ 8)))
          val = math.floor(val / (2 ^ 8))
        end
      else
        table.insert(bytes, string.char(math.floor(mantissa) % (2 ^ 8)))
        val = math.floor(mantissa / (2 ^ 8))
        table.insert(bytes, string.char(math.floor(val) % (2 ^ 8)))
        val = math.floor(val / (2 ^ 8))
      end

      table.insert(bytes, string.char(math.floor(exponent * ((opt == "d") and 16 or 128) + val) % (2 ^ 8)))
      val = math.floor((exponent * ((opt == "d") and 16 or 128) + val) / (2 ^ 8))
      table.insert(bytes, string.char(math.floor(sign * 128 + val) % (2 ^ 8)))
      val = math.floor((sign * 128 + val) / (2 ^ 8))

      if not endianness then
        table.insert(stream, string.reverse(table.concat(bytes)))
      else
        table.insert(stream, table.concat(bytes))
      end
    elseif opt == "s" then
      table.insert(stream, tostring(table.remove(vars, 1)))
      table.insert(stream, string.char(0))
    elseif opt == "c" then
      local n = format:sub(i + 1):match("%d+")
      local str = tostring(table.remove(vars, 1))
      local len = tonumber(n)
      if len <= 0 then
        len = str:len()
      end
      if len - str:len() > 0 then
        str = str .. string.rep(" ", len - str:len())
      end
      table.insert(stream, str:sub(1, len))
      i = i + n:len()
    end
  end

  return table.concat(stream)
end