Expansion of the TStreamerInfo actions.

[pcanal]

This add TStreamerInfo actions for the case of base class, nested objects, externally assignment streamer and array thereof (kBase, kAny, kStreamer, kStreamLoop) for both scalar and collection cases. It also expands the scope of the writing actions to cover the collections cases and the new cases (kBase, kAny, kStreamer, kStreamLoop)

Companion PR of root-project/roottest#1224

When executing the streaming on an object, the execution of the case covered by the case kBase, kAny, kStreamer, kStreamLoop was migrated from using the legacy code within the source file TStreamerInfoReadBuffer.cxx and TStreamerInfoWriteBuffer.cxx which is based on a pair of 'giant' switch statement to the newer framework based on the composition of TStreamerInfoActions (and the corresponding collection: TActionSequence). The change from switch statement to a set of function pointers allows to improve performance by executing for each data members only the code strictly necessary.

In its previous implementation (which is still used in a few rare cases involved backward compatibility), the case kBase (for both reading and writing) was forcing the use of the switch statement for all the data members of the base classes. This prevented the use of the new convert-on-write actions (with no existing corresponding implementation in the write switch statement) that are necessary for supporting the Enums with non default size.

[github-actions]

Test Results

    18 files      18 suites   3d 21h 3m 41s ⏱️
 2 687 tests  2 686 ✅ 0 💤 1 ❌
46 530 runs  46 529 ✅ 0 💤 1 ❌

For more details on these failures, see this check.

Results for commit 17097bc.

♻️ This comment has been updated with latest results.

[dpiparo]

Thanks for this major improvement. I added some comments for the review. In general I believe it could be very useful to take this opportunity, perhaps to the documentation of TStreamerInfo, to add a 1 page explanation of what this major overhaul does, also explaining simply, without code and only in English, what the pre-existing code was doing.

[pcanal]

to add a 1 page explanation of what this major overhaul does, also explaining simply, without code and only in English, what the pre-existing code was doing.

When executing the streaming on an object, the execution of the case covered by the case kBase, kAny, kStreamer, kStreamLoop was migrated from using the legacy code within the source file TStreamerInfoReadBuffer.cxx and TStreamerInfoWriteBuffer.cxx which is based on a pair of 'giant' switch statement to the newer framework based on the composition of TStreamerInfoActions (and the corresponding collection: TActionSequence). The change from switch statement to a set of function pointers allows to improve performance by executing for each data members only the code strictly necessary.

In its previous implementation (which is still used in a few rare cases involved backward compatibility), the case kBase (for both reading and writing) was forcing the use of the switch statement for all the data members of the base classes. This prevented the use of the new convert-on-write actions (with no existing corresponding implementation in the write switch statement) that are necessary for supporting the Enums with non default size.