Function read_rows 

fn read_rows(
    android: &dyn Android,
    files: &Files,
    wanted: &[Row],
    vault: &(PathBuf, [u8; 32]),
    region: Option<&Region>,
    budget: &mut u64,
) -> Option<Read>

The rows wanted read from Android in one question, taken in that order, each as it travels, its media put in the sharing within budget (the first medium of a step always). A multimedia message whose media do not fit stops the multimedia messages there for this step; the plain texts go on. A row gone meanwhile, or whose id another row took meanwhile, is left to the next listing. None when Android did not answer.