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/spruce-solutions/go-quai/common"
	"github.com/spruce-solutions/go-quai/core/state"
	"github.com/spruce-solutions/go-quai/core/types"
	"github.com/spruce-solutions/go-quai/params"
	"github.com/spruce-solutions/go-quai/rpc"
)

// ChainHeaderReader defines a small collection of methods needed to access the local
// blockchain during header verification.
type ChainHeaderReader 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

	// GetExternalBlocks retrieve all external blocks for a header.
	GetExternalBlocks(header *types.Header) ([]*types.ExternalBlock, error)

	// GetExternalBlocks retrieve all external link blocks for a header.
	GetLinkExternalBlocks(header *types.Header) ([]*types.ExternalBlock, error)

	// GetExternalBlock retrieves an external block header by its hash and context.
	GetExternalBlock(hash common.Hash, location []byte, context uint64) (*types.ExternalBlock, error)

	// QueueAndRetrieveExtBlocks passes external blocks to the queue and returns the amount available for this block
	QueueAndRetrieveExtBlocks(externalBlocks []*types.ExternalBlock, header *types.Header) []*types.ExternalBlock

	// GetUnclesInChain retrieves the uncles in the chain based on header.
	GetUnclesInChain(block *types.Block, length int) []*types.Header

	// GetGasUsedInChain gets the number value of gas used in the chain up until a certain number.
	GetGasUsedInChain(block *types.Block, length int) int64

	// CheckContextchecks to make sure the range of a context or order is valid
	CheckContext(context int) error

	// CheckLocationRange checks to make sure the range of r and z are valid
	CheckLocationRange(location []byte) error
}

// ChainReader defines a small collection of methods needed to access the local
// blockchain during header and/or uncle verification.
type ChainReader interface {
	ChainHeaderReader

	// 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 ChainHeaderReader, 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 ChainHeaderReader, 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

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

	// Finalize runs any post-transaction state modifications (e.g. block rewards)
	// but does not assemble the 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 ChainHeaderReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
		uncles []*types.Header)

	// FinalizeAndAssemble 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).
	FinalizeAndAssemble(chain ChainHeaderReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
		uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error)

	// GetExternalBlocks retrieves all valid external blocks from external chains
	GetExternalBlocks(chain ChainHeaderReader, header *types.Header, logging bool) ([]*types.ExternalBlock, error)

	// GetCoincidentAtOrder retrieves the coincident header.
	GetCoincidentAtOrder(chain ChainHeaderReader, context int, expectedOrder int, header *types.Header) (*types.Header, error)

	// CheckPrevHeaderCoincident checks if previous header is a coincident header.
	CheckPrevHeaderCoincident(chain ChainHeaderReader, context int, header *types.Header) (int, error)

	// This function determines the difficulty order of a block
	GetDifficultyOrder(header *types.Header) (int, error)

	// TraceBranches recursively traces region and zone branches to find external blocks.
	TraceBranches(chain ChainHeaderReader, header *types.Header, context int, originalContext int, originalLocation []byte) ([]*types.ExternalBlock, error)

	// GetLinkExternalBlocks links every block to the correct previous block
	GetLinkExternalBlocks(chain ChainHeaderReader, header *types.Header, logging bool) ([]*types.ExternalBlock, error)

	// PreviousCoincidentOnPath searches the path for a block of specified order in the specified slice
	PreviousCoincidentOnPath(chain ChainHeaderReader, header *types.Header, slice []byte, order, path int, fullSliceEqual bool) (*types.Header, 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 ChainHeaderReader, 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 ChainHeaderReader, time uint64, parent *types.Header, context int) *big.Int

	// APIs returns the RPC APIs this consensus engine provides.
	APIs(chain ChainHeaderReader) []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
}