The extension does not keep the files on disk opened like file_text functions do - rather, it grabs the content into a buffer, builds up a data structure representation of it, and converts back into a buffer and overwrites the file when saving.
You might be able to achieve a similar result for file_text functions by passing the string from a buffer into file_text_open_from_string, although I'm not sure where the limit is checked for.
Correct - for example, this works as intended and successfully prints values from 1024 different files:
// pre-generate 1024 INI files:
for (var i = 0; i < 1024; i++) {
var f = file_text_open_write("f" + string(i) + ".ini");
file_text_write_string(f, "[test]");
file_text_writeln(f);
file_text_write_string(f, "index=" + string(i));
file_text_close(f);
}
// open INIs:
for (var i = 0; i < 1024; i++) {
inis[i] = file_ini_open("f" + string(i) + ".ini");
}
// print values:
for (var i = 0; i < 1024; i++) {
show_debug_message(file_ini_read_real(inis[i], "test", "index", -1));
}