* Renamed source file clique_utils => clique_helpers
why:
New name is more in line with other modules where local libraries
are named similarly.
* re-implemented PoA verification module as clique_verify.nim
details:
The verification code was ported from the go sources and provisionally
stored in the clique_misc.nim source file.
todo:
Bring it to life.
* re-design Snapshot descriptor as: ref object
why:
Avoids some copying descriptor objects
details:
The snapshot management in clique_snapshot.nim has been cleaned up.
todo:
There is a lot of unnecessary copying & sub-list manipulation of
seq[BlockHeader] lists which needs to be simplified by managing
index intervals.
* optimised sequence handling for Clique/PoA
why:
To much ado about nothing
details:
* Working with shallow sequences inside PoA processing avoids
unnecessary copying.
* Using degenerate lists in the cliqueVerify() batch where only the
parent (and no other ancestor) is needed.
todo:
Expose only functions that are needed, shallow sequences should be
handles with care.
* fix var-parameter function argument
* Activate PoA engine -- currently proof of concept
details:
PoA engine is activated with newChain(extraValidation = true) applied
to a PoA network.
status and todo:
The extraValidation flag on the Chain object can be set at a later
state which allows to pre-load parts of the block chain without
verification. Setting it later will only go back the block chain to
the latest epoch checkpoint. This is inherent to the Clique protocol,
needs testing though.
PoA engine works in fine weather mode on Goerli replay. With the
canonical eip-225 tests, there are quite a few fringe conditions
that fail. These can easily fudged over to make things work but need
some more work to understand and correct properly.
* Make the last offending verification header available
why:
Makes some fringe case tests work.
details:
Within a failed transaction comprising several blocks, this
feature help to identify the offending block if there was a
PoA verification error.
* Make PoA header verifier store the final snapshot
why:
The last snapshot needed by the verifier is the one of the parent but
the list of authorised signer is derived from the current snapshot. So
updating to the latest snapshot provides the latest signers list.
details:
Also, PoA processing has been implemented as transaction in
persistBlocks() with Clique state rollback.
Clique tests succeed now.
* Avoiding double yields in iterator => replaced by template
why:
Tanks to Andri who observed it (see #762)
* Calibrate logging interval and fix logging event detection
why:
Logging interval as copied from Go implementation was too large and
needed re-calibration. Elapsed time calculation was bonkers, negative
the wrong way round.
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