what.lua

local table_insert = table.insert;
local string_byte, string_substr = string.byte, string.sub;
local bit_lshift, bit_bor = bit.lshift, bit.bor;

local function read_long(ptr, data)
	return ptr + 4, bit_bor(
		string_byte(data, ptr),
		bit_lshift(string_byte(data, ptr + 1), 8),
		bit_lshift(string_byte(data, ptr + 2), 16),
		bit_lshift(string_byte(data, ptr + 3), 24)
	);
end

local function read_null_string(ptr, data)
	local str_end = #data;
	for offset = ptr, str_end do
		if string_byte(data, offset) == 0 then str_end = offset break; end
	end
	return str_end + 1, string_substr(data, ptr, str_end - 1);
end

local HEADER = 23;
--[[
	buffer.Write( Addon::Ident, 4 );
	buffer.WriteType( ( char ) Addon::Version );
	buffer.WriteType( ( uint64_t ) 0ULL );
	buffer.WriteType( ( uint64_t ) Time::UnixTimestamp() );
	buffer.WriteType( ( char ) 0 ); // signifies nothing
]]
local function read_gma(data)
	local files = {};
	local data_block = 0;
	do
		local ptr = HEADER;
		ptr = (read_null_string(ptr, data)); -- buffer.WriteString( strTitle );
		ptr = (read_null_string(ptr, data)); -- buffer.WriteString( strDescription );
		ptr = (read_null_string(ptr, data)) + 4; -- buffer.WriteString( "Author Name" ); buffer.WriteType( ( int32_t ) 1 );
		local file_offset = 0;
		local str, size;
		while string_byte(data, ptr) ~= 0 do
			ptr, str  = read_null_string(ptr + 4, data);
			ptr, size = read_long(ptr, data);
			ptr = ptr + 8;
			table_insert(files, {
				str, size, file_offset, false
			});
			file_offset = file_offset + size
		end
		data_block = ptr + 4;
	end
	local index = 1
	return function()
		local file_entry = files[index];
		index = index + 1;
		if file_entry then
			local offset = data_block + file_entry[3];
			return file_entry[1], string_substr(data, offset, offset + file_entry[2] - 1);
		end
		return nil, nil;
	end;
end

for file_name, file_data in read_gma(file.Read("advdupe2.gma")) do
	print(file_name)
	print(string.sub(file_data, 1, 40))
end