* Renaming androgynous sub-object names according to where they belong
why:
These objects are not explicitly dealt with. They give meaning to
some generic wrapper objects. Naming them after their origin may
help troubleshooting.
* Redefine proof nodes list data type for `snap/1` wire protocol
why:
The current specification suffered from the fact that the basic data
type for a proof node is an RLP encoded hexary node. This slightly
confused the encoding/decoding magic.
details:
This is the second attempt, now wrapping the `seq[Blob]` into a
wrapper object of `seq[SnapProof]` for a distinct alias sequence.
In the previous attempt, `SnapProof` was a wrapper object holding the
`Blob` with magic applied to the `seq[]`. This needed the `append`
mixin to strip the outer wrapper that was applied to the `Blob` already
when it was passed as argument.
* Fix some prototype inconsistency
why:
For easy reading, `getAccountRange()` handler return code should
resemble the `accoundRange()` anruments prototype.
* Redefine `seq[Blob]` => `seq[SnapProof]` for `snap/1` protocol
why:
Proof nodes are traded as `Blob` type items rather than Nim objects. So
the RLP transcoder must not extra wrap proofs which are of type
seq[Blob]. Without custom encoding one would produce a
`list(blob(item1), blob(item2) ..)` instead of `list(item1, item2 ..)`.
* Limit leaf extractor by RLP size rather than number of items
why:
To be used serving `snap/1` requests, the result of function
`hexaryRangeLeafsProof()` is limited by the maximal space
needed to serialise the result which will be part of the
`snap/1` repsonse.
* Let the range extractor `hexaryRangeLeafsProof()` return RLP list sizes
why:
When collecting accounts, the size oft the accounts list when encoded
as RLP is continually updated. So the summed up value is available
anyway. For the proof nodes list, there are not many (~ 10) so summing
up is not expensive here.
* Unit tests to verify calculations based on hard coded constants
why:
Sizes of RLP encoded objects are available at run time only.
* Changed argument order for `hexaryRangeLeafsProof()` prototype
why:
Better to read as a stand-alone function (arguments were optimised
for functional pipelines)
* Run sub-range proof tests for extracted ranges
