core, eth, les: more efficient hash-based header chain retrieval (#16946)

1 files changed, 12 insertions, 0 deletions

diff --git a/light/lightchain.go b/light/lightchain.go
index 9d0a4e4f7..30b9bd89a 100644
--- a/light/lightchain.go
+++ b/light/lightchain.go
@@ -433,6 +433,18 @@ func (self *LightChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []c
 	return self.hc.GetBlockHashesFromHash(hash, max)
 }
 
+// GetAncestor retrieves the Nth ancestor of a given block. It assumes that either the given block or
+// a close ancestor of it is canonical. maxNonCanonical points to a downwards counter limiting the
+// number of blocks to be individually checked before we reach the canonical chain.
+//
+// Note: ancestor == 0 returns the same block, 1 returns its parent and so on.
+func (bc *LightChain) GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64) {
+	bc.chainmu.Lock()
+	defer bc.chainmu.Unlock()
+
+	return bc.hc.GetAncestor(hash, number, ancestor, maxNonCanonical)
+}
+
 // GetHeaderByNumber retrieves a block header from the database by number,
 // caching it (associated with its hash) if found.
 func (self *LightChain) GetHeaderByNumber(number uint64) *types.Header {