diff options
Diffstat (limited to 'core/headerchain.go')
| -rw-r--r-- | core/headerchain.go | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/core/headerchain.go b/core/headerchain.go index 2ac0cccc7..6e759ed1c 100644 --- a/core/headerchain.go +++ b/core/headerchain.go @@ -307,6 +307,43 @@ func (hc *HeaderChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []co return chain } +// 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 (hc *HeaderChain) GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64) { + if ancestor > number { + return common.Hash{}, 0 + } + if ancestor == 1 { + // in this case it is cheaper to just read the header + if header := hc.GetHeader(hash, number); header != nil { + return header.ParentHash, number - 1 + } else { + return common.Hash{}, 0 + } + } + for ancestor != 0 { + if rawdb.ReadCanonicalHash(hc.chainDb, number) == hash { + number -= ancestor + return rawdb.ReadCanonicalHash(hc.chainDb, number), number + } + if *maxNonCanonical == 0 { + return common.Hash{}, 0 + } + *maxNonCanonical-- + ancestor-- + header := hc.GetHeader(hash, number) + if header == nil { + return common.Hash{}, 0 + } + hash = header.ParentHash + number-- + } + return hash, number +} + // GetTd retrieves a block's total difficulty in the canonical chain from the // database by hash and number, caching it if found. func (hc *HeaderChain) GetTd(hash common.Hash, number uint64) *big.Int { |