Correct way to interpret row data when implementing custom postgres types?

[Boscop]

What is the correct way to interpret row data when implementing custom postgres types?

Diesel seems to use the binary protocol but how are geography points encoded in the binary protocol?

I'm trying to figure out how to get geography points working, are my assumptions correct here?
ThinkAlexandria/diesel_geometry#7 (comment)

When I convert the first 8 bytes of the EWKB string in reversed byte order to a f64, it shows a different value than what PgPoint shows as the first coordinate..

[Boscop]

Ah, I shouldn't reverse the byte order..
Now it shows the same value.

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But now the question arises, what's the correct way to serialize geography points?

Is it valid to write geography points as EWKB in any expression? such as in insert statements, or as argument to functions like ST_DWithin?

[weiznich]

I don't know the exact representation of every postgres type in libpq. This would be a better question for the libpq/postgis folks.
In general serialisation should just be the reverse operation of deserialisation, so just create the same thing you get FromSql::from_sql.

I close this issue because this is nothing actionable for diesel itself. (The representation is something that is defined by libpq/postgis)