`val default_output_filename : string`
`val set_current_output_filename : string ‑> unit`
`module Short_header : sig ... end`

Packs `Probe_id.t` and `Time_ns.t` into a single `int`.

`module Buffer : sig ... end`

Handles allocating `Iobuf.t` and making sure there's enough space in it.

`module Writer : sig ... end`

The `Writer` module contains functions that invoke parts of `Header_protocol` and `Short_header` in order to write into the relevant (global variable) buffers in `Buffer`