Round-trip C# byte[] as Lua string

[s5bug]

I'm working with a Lua script that requires binary data be written/read in string form (the io functions are operating on binary files). I cannot change this as I'm required to be backwards compatible with existing scripts. How do I register a function on the NLua context such that a byte[] is returned as a Lua string and not a System.Byte[]?

public byte[] ReadString(long /*nint*/ address, int length, bool absolute = false) {

01:00:07.931 ERR | NLua.Exceptions.LuaScriptException: ...Autosave.lua:59: bad argument #1 to 'write' (string expected, got System.Byte[], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)

This data is not valid UTF-8 and as such will not survive a raw → UTF16 → UTF8 roundtrip.

[viniciusjarina]

Can you write a test case?. I can't understand the error with this amount of information.
Maybe you need to use string.char and convert the byte array to Lua string
https://github.com/NLua/NLua/blob/main/tests/src/LuaTests.cs#L2956

[s5bug]

I cannot modify the extant Lua scripts, so using string.char is not an option for me.

Here's the script I'm working with:

if ReadInt(continue+0xC) ~= prevContinue and ReadByte(0x711438-offset2) == 0 and blacklisted == false then
    local f = io.open("KH2autosave.dat", "wb")
    f:write(ReadString(continue, 0x10FC0))
    f:close()
    ConsolePrint("Wrote autosave")
end

I am expected to implement ReadString. It must be able to:

• Read binary data from address 0x10FC0 from a byte buffer (not valid UTF-8 data, which is why using string will not work)
• Report that binary data to the Lua side as a Lua string for use with f:write

I can't write a test case for this unless the behavior of returning a byte[] from Lua#RegisterFunction should be changed to be Translated as a Lua string.

Here's the other side of the code, which can actually accept a byte[] due to the Translator supporting Lua string → C# byte[]:

local f = io.open("KH2autosave.dat", "rb")
if f ~= nil then
    WriteString(save1, f:read("*a"))
    f:close()
    ConsolePrint("Loaded autosave")
end