path: root/consensus/consensus.go

// 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/>.

// Package consensus implements different Ethereum consensus engines.
package consensus

import (
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/params"
    "github.com/ethereum/go-ethereum/rpc"
)

// ChainReader defines a small collection of methods needed to access the local
// blockchain during header and/or uncle verification.
type ChainReader interface {
    // Config retrieves the blockchain's chain configuration.
    Config() *params.ChainConfig

    // CurrentHeader retrieves the current header from the local chain.
    CurrentHeader() *types.Header

    // GetHeader retrieves a block header from the database by hash and number.
    GetHeader(hash common.Hash, number uint64) *types.Header

    // GetHeaderByNumber retrieves a block header from the database by number.
    GetHeaderByNumber(number uint64) *types.Header

    // GetHeaderByHash retrieves a block header from the database by its hash.
    GetHeaderByHash(hash common.Hash) *types.Header

    // GetBlock retrieves a block from the database by hash and number.
    GetBlock(hash common.Hash, number uint64) *types.Block
}

// Engine is an algorithm agnostic consensus engine.
type Engine interface {
    // Author retrieves the Ethereum address of the account that minted the given
    // block, which may be different from the header's coinbase if a consensus
    // engine is based on signatures.
    Author(header *types.Header) (common.Address, error)

    // VerifyHeader checks whether a header conforms to the consensus rules of a
    // given engine. Verifying the seal may be done optionally here, or explicitly
    // via the VerifySeal method.
    VerifyHeader(chain ChainReader, header *types.Header, seal bool) error

    // VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
    // concurrently. The method returns a quit channel to abort the operations and
    // a results channel to retrieve the async verifications (the order is that of
    // the input slice).
    VerifyHeaders(chain ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error)

    // VerifyUncles verifies that the given block's uncles conform to the consensus
    // rules of a given engine.
    VerifyUncles(chain ChainReader, block *types.Block) error

    // VerifySeal checks whether the crypto seal on a header is valid according to
    // the consensus rules of the given engine.
    VerifySeal(chain ChainReader, header *types.Header) error

    // Prepare initializes the consensus fields of a block header according to the
    // rules of a particular engine. The changes are executed inline.
    Prepare(chain ChainReader, header *types.Header) error

    // Finalize runs any post-transaction state modifications (e.g. block rewards)
    // and assembles the final block.
    // Note: The block header and state database might be updated to reflect any
    // consensus rules that happen at finalization (e.g. block rewards).
    Finalize(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
        uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error)

    // Seal generates a new sealing request for the given input block and pushes
    // the result into the given channel.
    //
    // Note, the method returns immediately and will send the result async. More
    // than one result may also be returned depending on the consensus algorithm.
    Seal(chain ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error

    // SealHash returns the hash of a block prior to it being sealed.
    SealHash(header *types.Header) common.Hash

    // CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
    // that a new block should have.
    CalcDifficulty(chain ChainReader, time uint64, parent *types.Header) *big.Int

    // APIs returns the RPC APIs this consensus engine provides.
    APIs(chain ChainReader) []rpc.API

    // Close terminates any background threads maintained by the consensus engine.
    Close() error
}

// PoW is a consensus engine based on proof-of-work.
type PoW interface {
    Engine

    // Hashrate returns the current mining hashrate of a PoW consensus engine.
    Hashrate() float64
}