Lua, dealing with non-ascii byte streams, byteorder change

Question

Need to encode & decode byte-stream (containing non-ascii characters possibly), from/into uint16, uint32, uint64 (their typical C/C++ meaning), taking care of endianness

Answer 1

Take a look at the struct and lpack libraries.

In this example, I use the struct.unpack to decode a Lua string into two integers with forced little-endian encoding:

require 'struct'
-- convert character codes to a Lua string - this may come from your source
local str = string.char(0x00, 0x1d, 0xff, 0x23, 0x44, 0x32)
-- format string: < = little endian, In = unsigned int (n bytes)
local u16, u32 = struct.unpack(' 7424    843326463