// Copyright 2017 The go-ethereum Authors// This file is part of the go-ethereum library.//// The go-ethereum library is free software: you can redistribute it and/or modify// it under the terms of the GNU Lesser General Public License as published by// the Free Software Foundation, either version 3 of the License, or// (at your option) any later version.//// The go-ethereum library is distributed in the hope that it will be useful,// but WITHOUT ANY WARRANTY; without even the implied warranty of// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the// GNU Lesser General Public License for more details.//// You should have received a copy of the GNU Lesser General Public License// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.packageconsensusimport"errors"var(// ErrUnknownAncestor is returned when validating a block requires an ancestor// that is unknown.ErrUnknownAncestor=errors.New("unknown ancestor")// ErrPrunedAncestor is returned when validating a block requires an ancestor// that is known, but the state of which is not available.ErrPrunedAncestor=errors.New("pruned ancestor")// ErrFutureBlock is returned when a block's timestamp is in the future according// to the current node.ErrFutureBlock=errors.New("block in the future")// ErrInvalidNumber is returned if a block's number doesn't equal its parent's// plus one.ErrInvalidNumber=errors.New("invalid block number"))