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nimbus-eth2/beacon_chain/consensus_object_pools/block_dag.nim

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# beacon_chain
# Copyright (c) 2018-2021 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.push raises: [Defect].}
import
chronicles,
../spec/datatypes/[phase0, altair, merge],
../spec/[helpers]
export chronicles, phase0, altair, merge, helpers
type
BlockId* = object
## A BlockId is the root and the slot in which that block was
## produced - there are no guarantees that this block is part of
## the canonical chain, or that we have validated it
root*: Eth2Digest
slot*: Slot
BlockSlotId* = object
## A BlockId at a slot equal to or higher than the slot of the block
bid*: BlockId
slot*: Slot
BlockRef* = ref object
## Node in object graph guaranteed to lead back to tail block, and to have
## a corresponding entry in database.
##
## All blocks identified by a `BlockRef` are valid per the state transition
## rules and that at some point were candidates for head selection. The
## ChainDAG offers stronger guarantees: it only returns `BlockRef` instances
## that are rooted in the currently finalized chain - however, these
## guarantees are valid only until the next head update - in particular,
## they are not valid across `await` calls.
##
## Block graph forms a tree - in particular, there are no cycles.
bid*: BlockId ##\
## Root that can be used to retrieve block data from database
parent*: BlockRef ##\
## Not nil, except for the tail
BlockSlot* = object
## Unique identifier for a particular fork and time in the block chain -
## normally, there's a block for every slot, but in the case a block is not
## produced, the chain progresses anyway, producing a new state for every
## slot.
blck*: BlockRef
slot*: Slot ##\
## Slot time for this BlockSlot which may differ from blck.slot when time
## has advanced without blocks
template root*(blck: BlockRef): Eth2Digest = blck.bid.root
template slot*(blck: BlockRef): Slot = blck.bid.slot
func init*(T: type BlockRef, root: Eth2Digest, slot: Slot): BlockRef =
BlockRef(
bid: BlockId(root: root, slot: slot)
)
func init*(T: type BlockRef, root: Eth2Digest, blck: SomeSomeBeaconBlock):
BlockRef =
BlockRef.init(root, blck.slot)
func toBlockId*(blck: SomeSomeSignedBeaconBlock): BlockId =
BlockId(root: blck.root, slot: blck.message.slot)
func toBlockId*(blck: ForkedSignedBeaconBlock): BlockId =
withBlck(blck): BlockId(root: blck.root, slot: blck.message.slot)
func parent*(bs: BlockSlot): BlockSlot =
## Return a blockslot representing the previous slot, using the parent block
## if the current slot had a block
if bs.slot == Slot(0):
BlockSlot(blck: nil, slot: Slot(0))
else:
BlockSlot(
blck: if bs.slot > bs.blck.slot: bs.blck else: bs.blck.parent,
slot: bs.slot - 1
)
func parentOrSlot*(bs: BlockSlot): BlockSlot =
## Return a blockslot representing the previous slot, using the parent block
## with the current slot if the current had a block
if bs.blck.isNil():
BlockSlot(blck: nil, slot: Slot(0))
elif bs.slot == bs.blck.slot:
BlockSlot(blck: bs.blck.parent, slot: bs.slot)
else:
BlockSlot(blck: bs.blck, slot: bs.slot - 1)
func getDepth*(a, b: BlockRef): tuple[ancestor: bool, depth: int] =
var b = b
var depth = 0
const maxDepth = (100'i64 * 365 * 24 * 60 * 60 div SECONDS_PER_SLOT.int)
while true:
if a == b:
return (true, depth)
# for now, use an assert for block chain length since a chain this long
# indicates a circular reference here..
doAssert depth < maxDepth
depth += 1
if a.slot >= b.slot or b.parent.isNil:
return (false, depth)
doAssert b.slot > b.parent.slot
b = b.parent
func isAncestorOf*(a, b: BlockRef): bool =
let (isAncestor, _) = getDepth(a, b)
isAncestor
func link*(parent, child: BlockRef) =
doAssert (not (parent.root == Eth2Digest() or child.root == Eth2Digest())),
"blocks missing root!"
doAssert parent.root != child.root, "self-references not allowed"
child.parent = parent
func get_ancestor*(blck: BlockRef, slot: Slot,
maxDepth = 100'i64 * 365 * 24 * 60 * 60 div SECONDS_PER_SLOT.int):
BlockRef =
## https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/phase0/fork-choice.md#get_ancestor
## Return the most recent block as of the time at `slot` that not more recent
## than `blck` itself
if isNil(blck): return nil
var blck = blck
var depth = 0
while true:
if blck.slot <= slot:
return blck
if isNil(blck.parent):
return nil
doAssert depth < maxDepth
depth += 1
blck = blck.parent
func atSlot*(blck: BlockRef, slot: Slot): BlockSlot =
## Return a BlockSlot at a given slot, with the block set to the closest block
## available. If slot comes from before the block, a suitable block ancestor
## will be used, else blck is returned as if all slots after it were empty.
## This helper is useful when imagining what the chain looked like at a
## particular moment in time, or when imagining what it will look like in the
## near future if nothing happens (such as when looking ahead for the next
## block proposal)
BlockSlot(blck: blck.get_ancestor(slot), slot: slot)
func atSlot*(blck: BlockRef): BlockSlot =
blck.atSlot(blck.slot)
func atSlot*(bid: BlockId, slot: Slot): BlockSlotId =
BlockSlotId(bid: bid, slot: slot)
func atSlot*(bid: BlockId): BlockSlotId =
bid.atSlot(bid.slot)
func atEpochStart*(blck: BlockRef, epoch: Epoch): BlockSlot =
## Return the BlockSlot corresponding to the first slot in the given epoch
atSlot(blck, epoch.compute_start_slot_at_epoch())
func atSlotEpoch*(blck: BlockRef, epoch: Epoch): BlockSlot =
## Return the last block that was included in the chain leading
## up to the given epoch - this amounts to the state at the time
## when epoch processing for `epoch` has been done, but no block
## has yet been applied
if epoch == GENESIS_EPOCH:
blck.atEpochStart(epoch)
else:
let start = epoch.compute_start_slot_at_epoch()
let tmp = blck.atSlot(start - 1)
if isNil(tmp.blck):
BlockSlot()
else:
tmp.blck.atSlot(start)
func toBlockSlotId*(bs: BlockSlot): BlockSlotId =
if isNil(bs.blck):
BlockSlotId()
else:
bs.blck.bid.atSlot(bs.slot)
func isProposed*(bid: BlockId, slot: Slot): bool =
## Return true if `bid` was proposed in the given slot
bid.slot == slot
func isProposed*(blck: BlockRef, slot: Slot): bool =
## Return true if `blck` was proposed in the given slot
not isNil(blck) and blck.isProposed(slot)
func isProposed*(bs: BlockSlot): bool =
## Return true if `bs` represents the proposed block (as opposed to an empty
## slot)
bs.blck.isProposed(bs.slot)
func isProposed*(bsi: BlockSlotId): bool =
## Return true if `bs` represents the proposed block (as opposed to an empty
## slot)
bsi.bid.isProposed(bsi.slot)
func shortLog*(v: BlockId): string =
# epoch:root when logging epoch, root:slot when logging slot!
shortLog(v.root) & ":" & $v.slot
func shortLog*(v: BlockSlotId): string =
# epoch:root when logging epoch, root:slot when logging slot!
if v.bid.slot == v.slot:
shortLog(v.bid)
else: # There was a gap - log it
shortLog(v.bid) & "@" & $v.slot
func shortLog*(v: BlockRef): string =
# epoch:root when logging epoch, root:slot when logging slot!
if v.isNil():
"nil:0"
else:
shortLog(v.bid)
func shortLog*(v: BlockSlot): string =
# epoch:root when logging epoch, root:slot when logging slot!
if isNil(v.blck):
"nil:0@" & $v.slot
elif v.blck.slot == v.slot:
shortLog(v.blck)
else: # There was a gap - log it
shortLog(v.blck) & "@" & $v.slot
chronicles.formatIt BlockId: shortLog(it)
chronicles.formatIt BlockSlotId: shortLog(it)
chronicles.formatIt BlockSlot: shortLog(it)
chronicles.formatIt BlockRef: shortLog(it)
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