func walk(ch *chain.Chain, hash, hdr []byte, height, blen, txs uint32) {
bh := btc.NewUint256(hash)
if _, ok := bidx[bh.Hash]; ok {
println("walk: ", bh.String(), "already in")
return
}
v := new(chain.BlockTreeNode)
v.BlockHash = bh
v.Height = height
v.BlockSize = blen
v.TxCount = txs
copy(v.BlockHeader[:], hdr)
bidx[bh.Hash] = v
cnt++
}
