https://arrow.apache.org/docs/format/IPC.html#file-format
<EOS [optional]: int32> If this stream marker is optional in the file format, doesn't this prevent someone from reading the file without being able to seek() it, e.g. if it is "piped in" to a program? Or otherwise they'll have to stream in the entire thing before they can start parsing? Any reason it can't be mandatory for a File? -John
