extend setAttribute to specify type

Sources/SwiftNetCDF/AttributeProvidable.swift

@@ -37,11 +37,14 @@ extension AttributeProvidable {
         try setAttribute(name, [value])
     }
 
-    /// Define a new attribute by name. The value must be a supported external type.
-    public func setAttribute<T: NetcdfConvertible>(_ name: String, _ value: [T]) throws {
-        let type = T.netcdfType.typeId
+    /// Define a new attribute by name. The value must be a supported external type. The type parameter can be set to enfore
+    public func setAttribute<T: NetcdfConvertible>(_ name: String, _ value: [T], type: ExternalDataType = T.netcdfType) throws {
+        guard T.canRead(type: type) else {
+            throw NetCDFError.datatypeNotCompatible
+        }
+
         try T.withPointer(to: value) { ptr in
-            try setAttributeRaw(name: name, type: type, length: value.count, ptr: ptr)
+            try setAttributeRaw(name: name, type: type.typeId, length: value.count, ptr: ptr)
         }
     }
 

Sources/SwiftNetCDF/Error.swift

@@ -33,6 +33,7 @@ public enum NetCDFError: Error {
     case hdf5Error
     case netCDF4MetedataError
     case alreadyExists
+    case datatypeNotCompatible
 
     /// Init from NetCDF error code
     /// TODO find NetCDF definiton for code 2 "no such file"

Tests/SwiftNetCDFTests/SwiftNetCDFTests.swift

@@ -12,6 +12,9 @@ final class SwiftNetCDFTests: XCTestCase {
         let file = try NetCDF.create(path: "test.nc", overwriteExisting: true)
         try file.setAttribute("TITLE", "My data set")
 
+        // Write attribute as [Char] instead of string with 0 terminator
+        try file.setAttribute("TITLE_CHAR", Array("My data set".utf8CString), type: .char)
+
         let dimensions = [
             try file.createDimension(name: "LAT", length: 10),
             try file.createDimension(name: "LON", length: 5)