Scopira 20080306

Input/output flows

Scopira includes its own input/output streaming flow facility. Features include:

  • Easy output for many type with the << operator.
  • Polymorphic architecture allows for the construction of layered, filtered data flows.
  • Fully serialization (object persistence) capabilities, include the ability to handle circular references.

Interfaces

Six primary interfaces are provided in the flow system. Three interfaces are for input:

And three interfaces are for output:

  • scopira::tool::ioflow_i writes raw bytes via two write() methods. A failed() method tests if the flow is in a failed state.
  • scopira::tool::iotflow_i builds on scopira::tool::ioflow_i by adding primitive type aware write methods. Primitives such as strings are included with the usual ints and doubles.
  • scopira::tool::ioobjflow_i builds on scopira::tool::iotflow_i by adding a scopira::tool::object-based serialization write method. This method stores type information about the object for later reconstruction by iiobjflow}.

End Flows

End flows are flow objects that take and produce data from concrete locations. These include:

Filtering Flows

Filtering flows provide flow classes that perform some kind of operations on the data flow as it passes to another flow. Filtering flows must always be connected to other flows and may be chained to perform stacked operations. Filters are organized into three tiers.

At the byte level (descendants from scopira::tool::iflow_i and scopira::tool::oflow_i) transformations are done on the raw byte stream itself:

  • scopira::tool::hexiflow and tool::hexiflow transform the stream into ASCII hex numbers. This is useful for storing arbitrary binary data in a text form.
  • scopira::tool::distoflow multiplexes its output to multiple tool::oflow_i objects.
  • scopira::tool::commentiflow is used to filter out comments from a file. A comment is defined as a # character in the first column, until end of line.
  • Future binary filtering flows could include those for checksum calculation, encryption and compression.

Type-level filters (those that descend from scopira::tool::itflow and scopira::tool::otflow) operate on primitive types and convert them to and from bytes. They connect to binary filters or end flows directly. They include:

Finally, object-level filters (those that descend from scopira::tool::iobjflow_i and scopira::tool::oobjflow_i) convert objects to a series of primitives. They connect to type-level filters. Two serialization (persistent) capable filters are provided:

  • scopira::tool::polyiflow and scopira::tool::polyoflow perform straight polymorphic serialization. This is the faster of the two streams but does not handle circular references, and stores duplicate object instances multiple times in the stream.
  • scopira::tool::isoiflow and scopira::tool::isooflow build on the polymorphic streams. They support circular references and record only references to previously saved object instances. This pair should be preferred when the data being serialized is potentially complex or circular.

Serializable Objects

To make your own objects serialization, see Object I/O