An optional facility for transcribing the outcome of runs of software.

§1. The telemetry file is optional, and transcribes the outcome of each run. This is mainly for testing Inform, but may also be useful for teachers who want to monitor how a whole class is using the system.

Nothing is done unless a filename is sent to the following function:

filename *spool_telemetry_to = NULL;
void Telemetry::locate_telemetry_file(filename *F) {
    spool_telemetry_to = F;
}

§2. A little lazily, the telemetry file once opened stays open until the process finishes.

int attempts_to_open_telemetry = 0;
text_stream telemetry_file_struct;  The actual telemetry file (if created)
text_stream *telemetry_file = &telemetry_file_struct;  Main telemetry stream
text_stream *telmy = NULL;  Current telemetry stream

void Telemetry::ensure_telemetry_file?Usage of Telemetry::ensure_telemetry_file:
§3
Problems, Level 0 - §9(void) {
    if (spool_telemetry_to == NULL) return;
    if (telmy) return;
    if (attempts_to_open_telemetry++ > 0) return;
    if (STREAM_OPEN_TO_FILE_APPEND(telemetry_file, spool_telemetry_to, ISO_ENC) == FALSE)
        Problems::fatal_on_file("Can't open telemetry file", spool_telemetry_to);
    telmy = telemetry_file;
    WRITE_TO(telmy, "\n-- -- -- -- -- -- -- --\n%B (build %B): telemetry.\n",
        FALSE, TRUE);
    int this_month = the_present->tm_mon + 1;
    int this_day = the_present->tm_mday;
    int this_year = the_present->tm_year + 1900;
    WRITE_TO(telmy, "Running on %4d-%02d-%02d at %02d:%02d.\n\n",
        this_year, this_month, this_day, the_present->tm_hour, the_present->tm_min);
    LOG("Opening telemetry file.\n");
}

§3. And log messages can be written here:

void Telemetry::write_to_telemetry_file(wchar_t *m) {
    Telemetry::ensure_telemetry_file();
    WRITE_TO(telmy, "The user says:\n\n%w\n\n", m);
}