General API Differences

General API Differences

The following is a list of general differences between the NI Driver C APIs and the gRPC API provided by grpc-device. These differences all affect all driver services in grpc-device.

• In attribute names, the abbreviation ATTR (as used in the C API) is spelled out as ATTRIBUTE in the gRPC API.
• In the gRPC API, parameter names are always snake case (e.g. example_parameter_name) rather than camel case (e.g. exampleParameterName), as used in the C API.
• The return value of the C API function will always be a field named status in the in the grpc-device Response message. statusOrRequiredSize in the C API is just called status in the gRPC API. For more information on this, refer to Array Size Parameters.
• Some functions in the C API use int32 parameters to represent booleans or enums. The corresponding functions in the gRPC API use enums or booleans for those parameters.

Array Size Parameters

Many functions in the C API that take in arrays also take in the array size. For example, the C prototype of RFmxBT_ModAccFetchDf1maxTrace is :

int32 __stdcall RFmxBT_ModAccFetchDf1maxTrace (niRFmxInstrHandle instrumentHandle, char selectorString[], float64 timeout, float32 time[], float32 df1max[], int32 arraySize, int32* actualArraySize);

Here, arraySize is just the size of the time and df1max parameters.

In the gRPC API, the arraySize parameter is not present; the gRPC layer automatically determines the correct value to pass in.

Additionally, some functions behave similarly for character arrays. For example, RFmxBT_GetError's parameter errorDescriptionBufferSize is present in the C API but absent in the gRPC API, because the gRPC layer automatically determines the necessary buffer size.

8- and 16-bit Integer types

protobuf does not support integer types narrower than 32 bits (see Scalar Value Types). When these types are used NI Driver C APIs, they are copy converted to or from the corresponding 32-bit type (int32 or uint32).