143 lines
4.4 KiB
Nim
143 lines
4.4 KiB
Nim
# nimbus-eth1
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# Copyright (c) 2021 Status Research & Development GmbH
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# Licensed under either of
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
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# http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
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# http://opensource.org/licenses/MIT)
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# at your option. This file may not be copied, modified, or distributed
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# except according to those terms.
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{.push raises: [].}
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import
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eth/[common, trie/nibbles],
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stew/results,
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"."/[aristo_desc, aristo_get]
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type
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Leg* = object
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## For constructing a `VertexPath`
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wp*: VidVtxPair ## Vertex ID and data ref
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nibble*: int8 ## Next vertex selector for `Branch` (if any)
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backend*: bool ## Sources from backend if `true`
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Hike* = object
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## Trie traversal path
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root*: VertexID ## Handy for some fringe cases
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legs*: seq[Leg] ## Chain of vertices and IDs
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tail*: NibblesSeq ## Portion of non completed path
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error*: AristoError ## Info for whoever wants it to see
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# ------------------------------------------------------------------------------
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# Private functions
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# ------------------------------------------------------------------------------
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func getNibblesImpl(hike: Hike; start = 0; maxLen = high(int)): NibblesSeq =
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## May be needed for partial rebuild, as well
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for n in start ..< min(hike.legs.len, maxLen):
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let leg = hike.legs[n]
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case leg.wp.vtx.vType:
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of Branch:
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result = result & @[leg.nibble.byte].initNibbleRange.slice(1)
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of Extension:
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result = result & leg.wp.vtx.ePfx
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of Leaf:
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result = result & leg.wp.vtx.lPfx
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# ------------------------------------------------------------------------------
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# Public functions
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# ------------------------------------------------------------------------------
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func to*(hike: Hike; T: type NibblesSeq): T =
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## Convert back
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hike.getNibblesImpl() & hike.tail
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func legsTo*(hike: Hike; T: type NibblesSeq): T =
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## Convert back
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hike.getNibblesImpl()
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# --------
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proc hikeUp*(
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path: NibblesSeq; # Partial path
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root: VertexID; # Start vertex
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db: AristoDbRef; # Database
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): Hike =
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## For the argument `path`, find and return the logest possible path in the
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## argument database `db`.
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result = Hike(
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root: root,
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tail: path)
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if not root.isValid:
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result.error = HikeRootMissing
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else:
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var vid = root
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while vid.isValid:
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var leg = Leg(wp: VidVtxPair(vid: vid), nibble: -1)
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# Fetch vertex to be checked on this lap
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leg.wp.vtx = db.top.sTab.getOrVoid vid
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if not leg.wp.vtx.isValid:
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# Register vertex fetched from backend (if any)
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let rc = db.getVtxBackend vid
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if rc.isErr:
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break
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leg.backend = true
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leg.wp.vtx = rc.value
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case leg.wp.vtx.vType:
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of Leaf:
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if result.tail.len == result.tail.sharedPrefixLen(leg.wp.vtx.lPfx):
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# Bingo, got full path
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result.legs.add leg
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result.tail = EmptyNibbleSeq
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else:
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result.error = HikeLeafTooEarly # Ooops
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break # Buck stops here
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of Branch:
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if result.tail.len == 0:
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result.legs.add leg
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result.error = HikeBranchTailEmpty # Ooops
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break
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let
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nibble = result.tail[0].int8
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nextVid = leg.wp.vtx.bVid[nibble]
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if not nextVid.isValid:
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result.error = HikeBranchBlindEdge # Ooops
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break
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leg.nibble = nibble
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result.legs.add leg
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result.tail = result.tail.slice(1)
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vid = nextVid
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of Extension:
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if result.tail.len == 0:
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result.legs.add leg
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result.tail = EmptyNibbleSeq
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result.error = HikeExtTailEmpty # Well, somehow odd
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break
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if leg.wp.vtx.ePfx.len != result.tail.sharedPrefixLen(leg.wp.vtx.ePfx):
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result.error = HikeExtTailMismatch # Need to branch from here
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break
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result.legs.add leg
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result.tail = result.tail.slice(leg.wp.vtx.ePfx.len)
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vid = leg.wp.vtx.eVid
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proc hikeUp*(lty: LeafTie; db: AristoDbRef): Hike =
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## Variant of `hike()`
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lty.path.to(NibblesSeq).hikeUp(lty.root, db)
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# ------------------------------------------------------------------------------
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# End
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# ------------------------------------------------------------------------------
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