Unlimited dimensions not supported

[andyclegg]

When creating a file with an unlimited dimension, data is not written properly.

package main

import "github.com/fhs/go-netcdf/netcdf"  
                  
func main() {                                                                    
    dataset, _ := netcdf.CreateFile("test.nc", netcdf.NETCDF4 | netcdf.WRITE)      
    dims := make([]netcdf.Dim, 1)                     
    dims[0], _ = dataset.AddDim("time", uint64(4))           
    ncvar, _ := dataset.AddVar("var", netcdf.FLOAT, dims)       
    dataset.EndDef()                                                
    ncvar.WriteFloat32s([]float32{0.1, 0.2, 0.3, 0.4})             
    dataset.Close()    
}        

Output of ncdump test.nc:

netcdf test {
dimensions:
	time = UNLIMITED ; // (0 currently)
variables:
	float var(time) ;
data:
}

However if the time dimension is defined as having a size of uint64(4) instead:

netcdf test {
dimensions:
	time = 4 ;
variables:
	float var(time) ;
data:

 var = 0.1, 0.2, 0.3, 0.4 ;
}

Unlimited dimensions are a very useful part of the netCDF specification and it would be great if they were supported.