Binary tx format for an array?

Hi there,

My question relates to trying to implement the binary transmission
protocol for an Array type. I understand that the only place the
format is documented is in the Postgres C source code.

I've had a look through it and it seems comprehensible enough (to a
non-C programmer), but I was wondering how the following expression
would evaluate:

// arrayfuncs.c, in array_recv
element_type = pq_getmsgint(buf, sizeof(Oid));

or more specifically, the

int size = sizeof(Oid);

expression. Knowing this value would mean knowing how many bytes
describing the Oid to transmit.

Cheers

Michael