[netcdfgroup] Single-Pass NetCDF

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: [netcdfgroup] Single-Pass NetCDF
• From: Elizabeth Fischer <rpf2116@xxxxxxxxxxxx>
• Date: Sun, 17 Jan 2016 19:07:45 -0500

Hello,

One of the biggest pains with NetCDF is having to write your I/O routines
three times: one for define, one for write and one for read.  I've
developed some techniques that greatly ease this burden; for many standard
cases, only a SINGLE subroutine needs to be written.  What I've done is in
C++, but it would apply equally well to Fortran 2003.

Would anyone be interested in exploring this further?  Example is below.

-- Elizabeth

```
void GridSpec_LonLat::ncio(ibmisc::NcIO &ncio, std::string const &vname)
{

auto lonb_d = get_or_add_dim(ncio,
vname + ".lon_boundaries.length", this->lonb.size());
ncio_vector(ncio, this->lonb, true,
vname + ".lon_boundaries", ncDouble, {lonb_d});

auto latb_d = get_or_add_dim(ncio,
vname + ".lat_boundaries.length", this->latb.size());
ncio_vector(ncio, this->latb, true,
vname + ".lat_boundaries", ncDouble, {latb_d});

NcVar info_v = get_or_add_var(ncio, vname + ".info", ncInt, {});
get_or_put_att(info_v, ncio.rw, "north_pole_cap", north_pole);
get_or_put_att(info_v, ncio.rw, "south_pole_cap", south_pole);
get_or_put_att(info_v, ncio.rw, "points_in_side", ncInt, points_in_side);
if (ncio.rw == 'w') {
int n;
n = nlon();
get_or_put_att(info_v, ncio.rw, "nlon", ncInt, n);
n = nlat();
get_or_put_att(info_v, ncio.rw, "nlat", ncInt, n);
}

}
```

To write:
```
ibmisc::NcIO ncio(spec.name + ".nc", netCDF::NcFile::replace);
spec.ncio(ncio, "grid");
ncio.close();
```

To read:
```
ibmisc::NcIO ncio(spec.name + ".nc", netCDF::NcFile::read);
spec.ncio(ncio, "grid");
ncio.close();
```