258 lines
9 KiB
Go
258 lines
9 KiB
Go
// Copyright (c) 2016-2017 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package blockchain
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import (
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"math"
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"github.com/btcsuite/btcd/chaincfg"
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)
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const (
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// vbLegacyBlockVersion is the highest legacy block version before the
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// version bits scheme became active.
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vbLegacyBlockVersion = 4
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// vbTopBits defines the bits to set in the version to signal that the
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// version bits scheme is being used.
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vbTopBits = 0x20000000
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// vbTopMask is the bitmask to use to determine whether or not the
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// version bits scheme is in use.
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vbTopMask = 0xe0000000
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// vbNumBits is the total number of bits available for use with the
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// version bits scheme.
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vbNumBits = 29
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)
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// bitConditionChecker provides a thresholdConditionChecker which can be used to
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// test whether or not a specific bit is set when it's not supposed to be
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// according to the expected version based on the known deployments and the
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// current state of the chain. This is useful for detecting and warning about
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// unknown rule activations.
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type bitConditionChecker struct {
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bit uint32
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chain *BlockChain
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}
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// Ensure the bitConditionChecker type implements the thresholdConditionChecker
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// interface.
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var _ thresholdConditionChecker = bitConditionChecker{}
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// BeginTime returns the unix timestamp for the median block time after which
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// voting on a rule change starts (at the next window).
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//
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// Since this implementation checks for unknown rules, it returns 0 so the rule
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// is always treated as active.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c bitConditionChecker) BeginTime() uint64 {
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return 0
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}
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// EndTime returns the unix timestamp for the median block time after which an
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// attempted rule change fails if it has not already been locked in or
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// activated.
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//
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// Since this implementation checks for unknown rules, it returns the maximum
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// possible timestamp so the rule is always treated as active.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c bitConditionChecker) EndTime() uint64 {
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return math.MaxUint64
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}
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// RuleChangeActivationThreshold is the number of blocks for which the condition
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// must be true in order to lock in a rule change.
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//
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// This implementation returns the value defined by the chain params the checker
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// is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c bitConditionChecker) RuleChangeActivationThreshold() uint32 {
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return c.chain.chainParams.RuleChangeActivationThreshold
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}
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// MinerConfirmationWindow is the number of blocks in each threshold state
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// retarget window.
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//
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// This implementation returns the value defined by the chain params the checker
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// is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c bitConditionChecker) MinerConfirmationWindow() uint32 {
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return c.chain.chainParams.MinerConfirmationWindow
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}
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// Condition returns true when the specific bit associated with the checker is
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// set and it's not supposed to be according to the expected version based on
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// the known deployments and the current state of the chain.
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//
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// This function MUST be called with the chain state lock held (for writes).
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c bitConditionChecker) Condition(node *blockNode) (bool, error) {
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conditionMask := uint32(1) << c.bit
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version := uint32(node.version)
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if version&vbTopMask != vbTopBits {
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return false, nil
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}
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if version&conditionMask == 0 {
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return false, nil
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}
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expectedVersion, err := c.chain.calcNextBlockVersion(node.parent)
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if err != nil {
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return false, err
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}
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return uint32(expectedVersion)&conditionMask == 0, nil
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}
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// deploymentChecker provides a thresholdConditionChecker which can be used to
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// test a specific deployment rule. This is required for properly detecting
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// and activating consensus rule changes.
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type deploymentChecker struct {
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deployment *chaincfg.ConsensusDeployment
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chain *BlockChain
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}
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// Ensure the deploymentChecker type implements the thresholdConditionChecker
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// interface.
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var _ thresholdConditionChecker = deploymentChecker{}
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// BeginTime returns the unix timestamp for the median block time after which
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// voting on a rule change starts (at the next window).
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//
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// This implementation returns the value defined by the specific deployment the
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// checker is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c deploymentChecker) BeginTime() uint64 {
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return c.deployment.StartTime
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}
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// EndTime returns the unix timestamp for the median block time after which an
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// attempted rule change fails if it has not already been locked in or
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// activated.
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//
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// This implementation returns the value defined by the specific deployment the
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// checker is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c deploymentChecker) EndTime() uint64 {
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return c.deployment.ExpireTime
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}
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// RuleChangeActivationThreshold is the number of blocks for which the condition
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// must be true in order to lock in a rule change.
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//
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// This implementation returns the value defined by the chain params the checker
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// is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c deploymentChecker) RuleChangeActivationThreshold() uint32 {
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return c.chain.chainParams.RuleChangeActivationThreshold
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}
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// MinerConfirmationWindow is the number of blocks in each threshold state
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// retarget window.
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//
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// This implementation returns the value defined by the chain params the checker
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// is associated with.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c deploymentChecker) MinerConfirmationWindow() uint32 {
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return c.chain.chainParams.MinerConfirmationWindow
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}
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// Condition returns true when the specific bit defined by the deployment
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// associated with the checker is set.
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//
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// This is part of the thresholdConditionChecker interface implementation.
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func (c deploymentChecker) Condition(node *blockNode) (bool, error) {
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conditionMask := uint32(1) << c.deployment.BitNumber
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version := uint32(node.version)
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return (version&vbTopMask == vbTopBits) && (version&conditionMask != 0),
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nil
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}
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// calcNextBlockVersion calculates the expected version of the block after the
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// passed previous block node based on the state of started and locked in
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// rule change deployments.
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//
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// This function differs from the exported CalcNextBlockVersion in that the
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// exported version uses the current best chain as the previous block node
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// while this function accepts any block node.
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//
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// This function MUST be called with the chain state lock held (for writes).
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func (b *BlockChain) calcNextBlockVersion(prevNode *blockNode) (int32, error) {
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// Set the appropriate bits for each actively defined rule deployment
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// that is either in the process of being voted on, or locked in for the
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// activation at the next threshold window change.
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expectedVersion := uint32(vbTopBits)
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for id := 0; id < len(b.chainParams.Deployments); id++ {
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deployment := &b.chainParams.Deployments[id]
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cache := &b.deploymentCaches[id]
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checker := deploymentChecker{deployment: deployment, chain: b}
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state, err := b.thresholdState(prevNode, checker, cache)
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if err != nil {
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return 0, err
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}
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if state == ThresholdStarted || state == ThresholdLockedIn {
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expectedVersion |= uint32(1) << deployment.BitNumber
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}
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}
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return int32(expectedVersion), nil
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}
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// CalcNextBlockVersion calculates the expected version of the block after the
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// end of the current best chain based on the state of started and locked in
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// rule change deployments.
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//
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// This function is safe for concurrent access.
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func (b *BlockChain) CalcNextBlockVersion() (int32, error) {
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b.chainLock.Lock()
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version, err := b.calcNextBlockVersion(b.bestChain.Tip())
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b.chainLock.Unlock()
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return version, err
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}
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// warnUnknownRuleActivations displays a warning when any unknown new rules are
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// either about to activate or have been activated. This will only happen once
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// when new rules have been activated and every block for those about to be
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// activated.
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//
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// This function MUST be called with the chain state lock held (for writes)
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func (b *BlockChain) warnUnknownRuleActivations(node *blockNode) error {
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// Warn if any unknown new rules are either about to activate or have
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// already been activated.
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for bit := uint32(0); bit < vbNumBits; bit++ {
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checker := bitConditionChecker{bit: bit, chain: b}
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cache := &b.warningCaches[bit]
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state, err := b.thresholdState(node.parent, checker, cache)
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if err != nil {
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return err
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}
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switch state {
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case ThresholdActive:
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if !b.unknownRulesWarned {
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log.Warnf("Unknown new rules activated (bit %d)",
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bit)
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b.unknownRulesWarned = true
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}
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case ThresholdLockedIn:
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window := int32(checker.MinerConfirmationWindow())
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activationHeight := window - (node.height % window)
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log.Warnf("Unknown new rules are about to activate in "+
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"%d blocks (bit %d)", activationHeight, bit)
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}
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}
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return nil
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}
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