codec-netcdf: Basic netcdf implementation

1 files changed, 106 insertions, 0 deletions

diff --git a/c++/codec-netcdf/netcdf.tmpl.h b/c++/codec-netcdf/netcdf.tmpl.h
new file mode 100644
index 0000000..921c84e
--- /dev/null
+++ b/c++/codec-netcdf/netcdf.tmpl.h
@@ -0,0 +1,106 @@
+#pragma once
+
+namespace saw {
+namespace impl {
+template<typename Schema>
+struct netcdf_is_group {
+		static constexpr bool value = false;
+};
+
+template<typename... T, string_literal... Lits>
+struct netcdf_is_group<schema::Struct<schema::Member<T,Lits>...>> {
+		static constexpr bool value = true;
+};
+
+template<typename Schema, typename RootSchema, typename ToEncode>
+struct netcdf_decode;
+
+template<typename RootSchema, typename ToDecode>
+struct netcdf_decode<schema::Int32, RootSchema, ToDecode> {
+		using Schema = schema::Int32;
+		static error_or<void> decode(data<Schema, ToDecode>& to, int from, int nc_varid){
+				int rc{};
+				
+				nc_type nc_vartype{};
+				int nc_dimnum{};
+				std::array<int,NC_MAX_VAR_DIMS> nc_dimids;
+
+				rc = nc_inq_var(from, nc_varid, nullptr, &nc_vartype, &nc_dimnum, &nc_dimids[0], nullptr);
+				if(rc != NC_NOERR){
+						return make_error<err::critical>();
+				}
+				if(nc_vartype != NC_INT){
+						return make_error<err::critical>();
+				}
+				if(nc_dimnum != 0){
+						return make_error<err::critical>();
+				}
+				
+				int32_t val{};
+				rc = nc_get_var_int(from, nc_varid, &val);
+				if(rc != NC_NOERR){
+						return make_error<err::critical>();
+				}
+
+				to.set(val);
+
+				return void_t {};
+		}
+};
+
+template<typename... T, string_literal... Lits, typename RootSchema, typename ToDecode>
+struct netcdf_decode<schema::Struct<schema::Member<T,Lits>...>, RootSchema, ToDecode> {
+	using Schema = schema::Struct<schema::Member<T,Lits>...>;
+
+	template<std::size_t i>
+	static error_or<void> decode_member(data<Schema,ToDecode>& to, int from){
+			using Type = typename parameter_pack_type<i,T...>::type;
+			constexpr string_literal Literal = parameter_key_pack_type<i, Lits...>::literal;
+			{
+				/**
+				 * We have to ask for the internal id of the netcdf structure
+				 */
+				if constexpr (netcdf_is_group<Type>::value){
+						int nc_group_id{};
+						int rc {};
+						rc = nc_inq_ncid(from, Literal.data.data(), &nc_group_id);
+						if(rc != NC_NOERR) {
+								return make_error<err::critical>();
+						}
+						auto eov = netcdf_decode<Type, RootSchema, ToDecode>::decode(to.template get<Literal>(), nc_group_id);
+						if(eov.is_error()){
+								return eov;
+						}
+				}else{
+						int nc_varid{};
+						int rc {};
+						rc = nc_inq_varid(from, Literal.data.data(), &nc_varid);
+						if(rc != NC_NOERR) {
+								return make_error<err::critical>();
+						}
+						auto eov = netcdf_decode<Type, RootSchema, ToDecode>::decode(to.template get<Literal>(), from, nc_varid); 
+				}
+
+			}
+			if constexpr ((i+1) < sizeof...(T)){
+				auto eov = decode_member<i+1>(from, to, ncid);
+				if(eov.is_error()){
+						return eov;
+				}
+			}
+
+			return void_t{};
+	}
+
+
+	static error_or<void> decode(data<Schema, ToDecode>& to, int from){
+		if constexpr (sizeof...(T) > 0){
+				auto eov = decode_member<0>(to, from);
+				return eov;
+		}
+		
+		return void_t{};
+	}
+};
+}
+}