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Comparing 2 UInt64 in Lua

I am trying to print "No Value" on certain 64bit nullable sentinel values for SBE protocols. Here is a code example:

-- Size: Cross Id
size_of.cross_id = 8

-- Display: Cross Id
display.cross_id = function(value)
  -- Check if field has value
  if value == 18446744073709551615 then
    return "Cross Id: No Value ("..value..")"
  end

  return "Cross Id: "..value
end

-- Dissect: Cross Id
dissect.cross_id = function(buffer, offset, packet, parent)
  local length = size_of.cross_id
  local range = buffer(offset, length)
  local value = range:le_uint64()
  local display = display.cross_id(value, buffer, offset, packet, parent)

  parent:add(cme_futures_ilink3_sbe_v8_7.fields.cross_id, range, value, display)

  return offset + length, value
end

This script prints 18446744073709551615 for the null values. I know the 64 bit types have special handling. What is the cleanest method to handle this type?

Comparing 2 UInt64 in Lua

I am trying to print "No Value" on certain 64bit nullable sentinel values for SBE protocols. Here is a code example:

-- Size: Cross Id
size_of.cross_id = 8

-- Display: Cross Id
display.cross_id = function(value)
  -- Check if field has value
  if value == 18446744073709551615 then
    return "Cross Id: No Value ("..value..")"
  end

  return "Cross Id: "..value
end

-- Dissect: Cross Id
dissect.cross_id = function(buffer, offset, packet, parent)
  local length = size_of.cross_id
  local range = buffer(offset, length)
  local value = range:le_uint64()
  local display = display.cross_id(value, buffer, offset, packet, parent)

  parent:add(cme_futures_ilink3_sbe_v8_7.fields.cross_id, range, value, display)

  return offset + length, value
end

This script prints 18446744073709551615 for the null values. I know the 64 bit types have special handling. What is the cleanest method to handle this type?