Improve WkbWriter constructors

[pka]

This PR adresses #156 (first commit) and should fix different dimensions in reader and writer (second commit).

Follow-up to discussion with @Oreilles in #153 (comment)

Instead of the ugly with_extended_opts constructor we should probably use a builder pattern.

[nyurik]

I think this is a good direction, thx! Would it make sense to perhaps simplify all readers/writers to own underlying impl Read/impl Write? Same as std::io::BufWriter and others? The wrappers would still allow access to the underlying inner reader/writer, same as buffer - with get_ref and get_mut

[Oreilles]

Thanks for solving this, I was about to go at it when I saw your PR 🙂

Regarding the constructor issue: I don't know if that's a common pattern in rust, but in Typescript you often create functions accepting a single parameter object containing all the options, rather than one function argument for each parameter. It makes it easier to merge default values and reduce friction with adding new options. It has the disadvantage of being a bit more verbose though.

In this case, it could look something like this (untested):

#[derive(Default)]
pub struct WkbWriterParams {
    pub dialect: WkbDialect,
    pub dims: CoordDimensions,
    pub srid: Option<i32>,
    pub envelope: Vec<f64>,
    pub envelope_dims: CoordDimensions,
    pub extended_gpkg: bool,
}

impl<'a, W: Write> WkbWriter<'a, W> {
    pub fn new(out: &'a mut W, params: WkbWriterParams) -> WkbWriter<'a, W> {
        WkbWriter {
            dialect: params.dialect,
            dims: params.dims,
            srid: params.srid,
            envelope: params.envelope,
            envelope_dims: params.envelope_dims,
            extended_gpkg: params.extended_gpkg,
            empty: false,
            endian: scroll::LE,
            dialect,
            first_header: true,
            geom_state: GeomState::Normal,
            out,
        }
    }
}

// Or even just: 
impl<'a, W: Write> WkbWriter<'a, W> {
    pub fn new(out: &'a mut W, params: WkbWriterParams) -> WkbWriter<'a, W> {
        WkbWriter {
            params,
            empty: false,
            endian: scroll::LE,
            dialect,
            first_header: true,
            geom_state: GeomState::Normal,
            out,
        }
    }
}

which you would then call as such:

let writer = WkbWriter::new(out, WkbWriterParams { srid: Some(4326), Default::default() })

[nyurik]

Rust usually uses builder pattern as it is far more concise and does not break when options are changed, e.g. this guide. The biggest unknown is if the builder should return &mut Self or Self on each setter

[pka]

I'm hesitating to put too much work into this mostly internal API. We could also implement Default for writer structs instead of having with_extended_opts or builder functions. But implementingDefault isn't easy because of out: &'a mut W. So yes, we should probably switch to out: W.

[michaelkirk]

So yes, we should probably switch to out: W.

This is done in #162

[nyurik]

eeek! ok :)

[nyurik]

these two vars are not really needed - too little value, but i guess they are ok if we will switch to a builder soon