C++: IWriteable and IChunkWriter semantic mix

[ciprianf]

Hi,

In C++, the IChunkWriter inherits from publicly the interface IWritable and modifies semantically the end method. Whereas for IWritable end means "all writing is finished, you can close and finalize", in the IChunkWriter it means only the current chunk is finalized, and the writer can be reused after a call to clear.

Having thus a pointer to an object of type IWritable*, one does not really know what end() means or should supposed to do. This pattern breaks polymorphism. It looks like two distinct layers are conflated through this inheritance:

• layer 1: final stream / file destination.
• layer 2: in-memory compression boundary.

One has to pay attention to these details if wanting to implement custom IWritables.