Detailed Description

Data source backend for variable nodes.

The server redirects every read and write request to callback functions. Internally, the data source needs to implement its own memory management.

Definition at line 45 of file nodestore.hpp.

Public Attributes
std::function< StatusCode(DataValue &value, const NumericRange &range, bool timestamp)>	read

std::function< StatusCode(const DataValue &value, const NumericRange &range)>	write

Member Data Documentation

std::function<StatusCode(DataValue& value, const NumericRange& range, bool timestamp)> opcua::ValueBackendDataSource::read

Callback to set the read value, the result status and optionally a source timestamp.

Note: Zero-copy operations are possible. It is not required to return a copy of the actual content data. You can return a pointer to memory owned by the user. Memory can be reused between read callbacks of a data source, as the result is already encoded on the network buffer between each read operation. To use zero-copy reads, set the value of the Variant (DataValue::getValue) without copying, e.g. with Variant::setScalar or Variant::setArray.

Parameters

value	The DataValue that is returned to the reader
range	If not empty, then the data source shall return only a selection of the (nonscalar) data. Set `UA_STATUSCODE_BADINDEXRANGEINVALID` in `value` if this does not apply
timestamp	Set the source timestamp of `value` if `true`

Definition at line 63 of file nodestore.hpp.

std::function<StatusCode(const DataValue& value, const NumericRange& range)> opcua::ValueBackendDataSource::write

Callback to write the value into a data source.

This function can be empty if the operation is unsupported.

Parameters

value	The DataValue that has been written by the writer
range	If not empty, then only this selection of (non-scalar) data should be written into the data source

Definition at line 74 of file nodestore.hpp.