clique的挖矿的信任节点

// Snapshot is the state of the authorization voting at a given point in time.type Snapshot struct {    config   *params.CliqueConfig // Consensus engine parameters to fine tune behavior    sigcache *lru.ARCCache        // Cache of recent block signatures to speed up ecrecover    Number  uint64                      `json:"number"`  // Block number where the snapshot was created    Hash    common.Hash                 `json:"hash"`    // Block hash where the snapshot was created    Signers map[common.Address]struct{} `json:"signers"` // Set of authorized signers at this moment    Recents map[uint64]common.Address   `json:"recents"` // Set of recent signers for spam protections    Votes   []*Vote                     `json:"votes"`   // List of votes cast in chronological order    Tally   map[common.Address]Tally    `json:"tally"`   // Current vote tally to avoid recalculating}

func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {    ...    number := header.Number.Uint64()    ...    signer, signFn := c.signer, c.signFn    ...    // Bail out if we're unauthorized to sign a block    snap, err := c.snapshot(chain, number-1, header.ParentHash, nil)    ...    // If we're amongst the recent signers, wait for the next block    for seen, recent := range snap.Recents {        if recent == signer {            // Signer is among recents, only wait if the current block doesn't shift it out            if limit := uint64(len(snap.Signers)/2 + 1); number < limit || seen > number-limit {                log.Info("Signed recently, must wait for others")                <-stop                return nil, nil            }        }    }    ...}

// validVote returns whether it makes sense to cast the specified vote in the// given snapshot context (e.g. don't try to add an already authorized signer).func (s *Snapshot) validVote(address common.Address, authorize bool) bool {    _, signer := s.Signers[address]    return (signer && !authorize) || (!signer && authorize)}

func (s *Snapshot) apply(headers []*types.Header) (*Snapshot, error) {    ...    snap := s.copy()    for _, header := range headers {        // Remove any votes on checkpoint blocks        number := header.Number.Uint64()        if number%s.config.Epoch == 0 {            snap.Votes = nil            snap.Tally = make(map[common.Address]Tally)        }        ...        signer, err := ecrecover(header, s.sigcache)        ...        // If the vote passed, update the list of signers        if tally := snap.Tally[header.Coinbase]; tally.Votes > len(snap.Signers)/2 {            if tally.Authorize {                snap.Signers[header.Coinbase] = struct{}{}            } else {                delete(snap.Signers, header.Coinbase)                ...            }        }    }    ...}