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[NOD-226] Fix comments around BlockLocator (#334)

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* [NOD-226] Corrected blockLocator-related comments.

* [NOD-226] Fixed "current tips" -> "selected tip".
This commit is contained in:
stasatdaglabs 2019-06-30 12:34:53 +03:00 committed by Ori Newman
parent c14c64d534
commit 589763e8ec
1 changed files with 18 additions and 22 deletions
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40
blockdag/dag.go
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@ -32,19 +32,18 @@ const (
)
// BlockLocator is used to help locate a specific block. The algorithm for
// building the block locator is to add the hashes in reverse order until
// the genesis block is reached. In order to keep the list of locator hashes
// to a reasonable number of entries, first the most recent previous 12 block
// hashes are added, then the step is doubled each loop iteration to
// exponentially decrease the number of hashes as a function of the distance
// from the block being located.
// building the block locator is to add block hashes in reverse order on the
// block's selected parent chain until the genesis block is reached.
// In order to keep the list of locator hashes to a reasonable number of entries,
// the step between each entry is doubled each loop iteration to exponentially
// decrease the number of hashes as a function of the distance from the block
// being located.
//
// For example, assume a block chain with a side chain as depicted below:
// For example, assume a selected parent chain with IDs as depicted below:
// genesis -> 1 -> 2 -> ... -> 15 -> 16 -> 17 -> 18
// \-> 16a -> 17a
//
// The block locator for block 17a would be the hashes of blocks:
// [17a 16a 15 14 13 12 11 10 9 8 7 6 4 genesis]
// The block locator for block 17 would be the hashes of blocks:
// [17 16 14 11 7 2 genesis]
type BlockLocator []*daghash.Hash
// orphanBlock represents a block that we don't yet have the parent for. It
@ -1376,8 +1375,8 @@ func (dag *BlockDAG) HeaderByHash(hash *daghash.Hash) (*wire.BlockHeader, error)
// See BlockLocator for details on the algorithm used to create a block locator.
//
// In addition to the general algorithm referenced above, this function will
// return the block locator for the selected tip if
// the passed hash is not currently known.
// return the block locator for the selected tip if the passed hash is not currently
// known.
//
// This function is safe for concurrent access.
func (dag *BlockDAG) BlockLocatorFromHash(hash *daghash.Hash) BlockLocator {
@ -1393,8 +1392,7 @@ func (dag *BlockDAG) BlockLocatorFromHash(hash *daghash.Hash) BlockLocator {
return locator
}
// LatestBlockLocator returns a block locator for the latest known tip of the
// main (best) chain.
// LatestBlockLocator returns a block locator for the current tips of the DAG.
//
// This function is safe for concurrent access.
func (dag *BlockDAG) LatestBlockLocator() BlockLocator {
@ -1405,8 +1403,8 @@ func (dag *BlockDAG) LatestBlockLocator() BlockLocator {
}
// blockLocator returns a block locator for the passed block node. The passed
// node can be nil in which case the block locator for the current tip
// associated with the view will be returned.
// node can be nil in which case the block locator for the selected tip will be
// returned.
//
// See the BlockLocator type comments for more details.
//
@ -1588,9 +1586,8 @@ func (dag *BlockDAG) locateInventory(locator BlockLocator, hashStop *daghash.Has
return stopNode, 1
}
// Find the most recent locator block hash in the main chain. In the
// case none of the hashes in the locator are in the main chain, fall
// back to the genesis block.
// Find the most recent locator block hash in the DAG. In the case none of
// the hashes in the locator are in the DAG, fall back to the genesis block.
startNode := dag.genesis
for _, hash := range locator {
node := dag.index.LookupNode(hash)
@ -1629,9 +1626,8 @@ func (dag *BlockDAG) locateBlocks(locator BlockLocator, hashStop *daghash.Hash,
}
func (dag *BlockDAG) locateBlockNodes(locator BlockLocator, hashStop *daghash.Hash, maxEntries uint32) []*blockNode {
// Find the first known block in the locator and the
// estimated number of nodes after it needed while respecting the stop hash
// and max entries.
// Find the first known block in the locator and the estimated number of
// nodes after it needed while respecting the stop hash and max entries.
node, estimatedEntries := dag.locateInventory(locator, hashStop, maxEntries)
if estimatedEntries == 0 {
return nil