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generator.go
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generator.go
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// Copyright (c) 2016-2017 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package chaingen
import (
"bytes"
"encoding/binary"
"fmt"
"math"
"math/big"
"runtime"
"sort"
"time"
"github.com/hybridnetwork/hxd/blockchain"
"github.com/hybridnetwork/hxd/chaincfg"
"github.com/hybridnetwork/hxd/chaincfg/chainhash"
"github.com/hybridnetwork/hxd/txscript"
"github.com/hybridnetwork/hxd/wire"
dcrutil "github.com/hybridnetwork/hxutil"
)
var (
// hash256prngSeedConst is a constant derived from the hex
// representation of pi and is used in conjuction with a caller-provided
// seed when initializing the deterministic lottery prng.
hash256prngSeedConst = []byte{0x24, 0x3f, 0x6a, 0x88, 0x85, 0xa3, 0x08,
0xd3}
// opTrueScript is a simple public key script that contains the OP_TRUE
// opcode. It is defined here to reduce garbage creation.
opTrueScript = []byte{txscript.OP_TRUE}
// opTrueRedeemScript is the signature script that can be used to redeem
// a p2sh output to the opTrueScript. It is defined here to reduce
// garbage creation.
opTrueRedeemScript = []byte{txscript.OP_DATA_1, txscript.OP_TRUE}
// coinbaseSigScript is the signature script used by the tests when
// creating standard coinbase transactions. It is defined here to
// reduce garbage creation.
coinbaseSigScript = []byte{txscript.OP_0, txscript.OP_0}
)
const (
// voteBitYes is the specific bit that is set in the vote bits to
// indicate that the previous block is valid.
voteBitYes = 0x01
)
// SpendableOut represents a transaction output that is spendable along with
// additional metadata such as the block its in and how much it pays.
type SpendableOut struct {
prevOut wire.OutPoint
blockHeight uint32
blockIndex uint32
amount dcrutil.Amount
}
// PrevOut returns the outpoint associated with the spendable output.
func (s *SpendableOut) PrevOut() wire.OutPoint {
return s.prevOut
}
// BlockHeight returns the block height of the block the spendable output is in.
func (s *SpendableOut) BlockHeight() uint32 {
return s.blockHeight
}
// BlockIndex returns the offset into the block the spendable output is in.
func (s *SpendableOut) BlockIndex() uint32 {
return s.blockIndex
}
// Amount returns the amount associated with the spendable output.
func (s *SpendableOut) Amount() dcrutil.Amount {
return s.amount
}
// MakeSpendableOutForTx returns a spendable output for the given transaction
// block height, transaction index within the block, and transaction output
// index within the transaction.
func MakeSpendableOutForTx(tx *wire.MsgTx, blockHeight, txIndex, txOutIndex uint32) SpendableOut {
return SpendableOut{
prevOut: wire.OutPoint{
Hash: *tx.CachedTxHash(),
Index: txOutIndex,
Tree: wire.TxTreeRegular,
},
blockHeight: blockHeight,
blockIndex: txIndex,
amount: dcrutil.Amount(tx.TxOut[txOutIndex].Value),
}
}
// MakeSpendableOut returns a spendable output for the given block, transaction
// index within the block, and transaction output index within the transaction.
func MakeSpendableOut(block *wire.MsgBlock, txIndex, txOutIndex uint32) SpendableOut {
tx := block.Transactions[txIndex]
return MakeSpendableOutForTx(tx, block.Header.Height, txIndex, txOutIndex)
}
// stakeTicket represents a transaction that is an sstx along with the height of
// the block it was mined in and the its index within that block.
type stakeTicket struct {
tx *wire.MsgTx
blockHeight uint32
blockIndex uint32
}
// stakeTicketSorter implements sort.Interface to allow a slice of stake tickets
// to be sorted.
type stakeTicketSorter []*stakeTicket
// Len returns the number of stake tickets in the slice. It is part of the
// sort.Interface implementation.
func (t stakeTicketSorter) Len() int { return len(t) }
// Swap swaps the stake tickets at the passed indices. It is part of the
// sort.Interface implementation.
func (t stakeTicketSorter) Swap(i, j int) { t[i], t[j] = t[j], t[i] }
// Less returns whether the stake ticket with index i should sort before the
// stake ticket with index j. It is part of the sort.Interface implementation.
func (t stakeTicketSorter) Less(i, j int) bool {
iHash := t[i].tx.CachedTxHash()[:]
jHash := t[j].tx.CachedTxHash()[:]
return bytes.Compare(iHash, jHash) < 0
}
// Generator houses state used to ease the process of generating test blocks
// that build from one another along with housing other useful things such as
// available spendable outputs and generic payment scripts used throughout the
// tests.
type Generator struct {
params *chaincfg.Params
tip *wire.MsgBlock
tipName string
blocks map[chainhash.Hash]*wire.MsgBlock
blocksByName map[string]*wire.MsgBlock
p2shOpTrueAddr dcrutil.Address
p2shOpTrueScript []byte
// Used for tracking spendable coinbase outputs.
spendableOuts [][]SpendableOut
prevCollectedHash chainhash.Hash
// Used for tracking the live ticket pool.
originalParents map[chainhash.Hash]chainhash.Hash
immatureTickets []*stakeTicket
liveTickets []*stakeTicket
wonTickets map[chainhash.Hash][]*stakeTicket
expiredTickets []*stakeTicket
}
// MakeGenerator returns a generator instance initialized with the genesis block
// as the tip as well as a cached generic pay-to-script-hash script for OP_TRUE.
func MakeGenerator(params *chaincfg.Params) (Generator, error) {
// Generate a generic pay-to-script-hash script that is a simple
// OP_TRUE. This allows the tests to avoid needing to generate and
// track actual public keys and signatures.
p2shOpTrueAddr, err := dcrutil.NewAddressScriptHash(opTrueScript, params)
if err != nil {
return Generator{}, err
}
p2shOpTrueScript, err := txscript.PayToAddrScript(p2shOpTrueAddr)
if err != nil {
return Generator{}, err
}
genesis := params.GenesisBlock
genesisHash := genesis.BlockHash()
return Generator{
params: params,
tip: genesis,
tipName: "genesis",
blocks: map[chainhash.Hash]*wire.MsgBlock{genesisHash: genesis},
blocksByName: map[string]*wire.MsgBlock{"genesis": genesis},
p2shOpTrueAddr: p2shOpTrueAddr,
p2shOpTrueScript: p2shOpTrueScript,
originalParents: make(map[chainhash.Hash]chainhash.Hash),
wonTickets: make(map[chainhash.Hash][]*stakeTicket),
}, nil
}
// Params returns the chain params associated with the generator instance.
func (g *Generator) Params() *chaincfg.Params {
return g.params
}
// Tip returns the current tip block of the generator instance.
func (g *Generator) Tip() *wire.MsgBlock {
return g.tip
}
// TipName returns the name of the current tip block of the generator instance.
func (g *Generator) TipName() string {
return g.tipName
}
// BlockByName returns the block associated with the provided block name. It
// will panic if the specified block name does not exist.
func (g *Generator) BlockByName(blockName string) *wire.MsgBlock {
block, ok := g.blocksByName[blockName]
if !ok {
panic(fmt.Sprintf("block name %s does not exist", blockName))
}
return block
}
// BlockByHash returns the block associated with the provided block hash. It
// will panic if the specified block hash does not exist.
func (g *Generator) BlockByHash(hash *chainhash.Hash) *wire.MsgBlock {
block, ok := g.blocks[*hash]
if !ok {
panic(fmt.Sprintf("block with hash %s does not exist", hash))
}
return block
}
// opReturnScript returns a provably-pruneable OP_RETURN script with the
// provided data.
func opReturnScript(data []byte) []byte {
builder := txscript.NewScriptBuilder()
script, err := builder.AddOp(txscript.OP_RETURN).AddData(data).Script()
if err != nil {
panic(err)
}
return script
}
// UniqueOpReturnScript returns a standard provably-pruneable OP_RETURN script
// with a random uint64 encoded as the data.
func UniqueOpReturnScript() []byte {
rand, err := wire.RandomUint64()
if err != nil {
panic(err)
}
data := make([]byte, 8, 8)
binary.LittleEndian.PutUint64(data[0:8], rand)
return opReturnScript(data)
}
// calcFullSubsidy returns the full block subsidy for the given block height.
//
// NOTE: This and the other subsidy calculation funcs intentionally are not
// using the blockchain code since the intent is to be able to generate known
// good tests which exercise that code, so it wouldn't make sense to use the
// same code to generate them.
func (g *Generator) calcFullSubsidy(blockHeight uint32) dcrutil.Amount {
iterations := int64(blockHeight) / g.params.SubsidyReductionInterval
subsidy := g.params.BaseSubsidy
for i := int64(0); i < iterations; i++ {
subsidy *= g.params.MulSubsidy
subsidy /= g.params.DivSubsidy
}
return dcrutil.Amount(subsidy)
}
// calcPoWSubsidy returns the proof-of-work subsidy portion from a given full
// subsidy, block height, and number of votes that will be included in the
// block.
//
// NOTE: This and the other subsidy calculation funcs intentionally are not
// using the blockchain code since the intent is to be able to generate known
// good tests which exercise that code, so it wouldn't make sense to use the
// same code to generate them.
func (g *Generator) calcPoWSubsidy(fullSubsidy dcrutil.Amount, blockHeight uint32, numVotes uint16) dcrutil.Amount {
powProportion := dcrutil.Amount(g.params.WorkRewardProportion)
totalProportions := dcrutil.Amount(g.params.TotalSubsidyProportions())
powSubsidy := (fullSubsidy * powProportion) / totalProportions
if int64(blockHeight) < g.params.StakeValidationHeight {
return powSubsidy
}
// Reduce the subsidy according to the number of votes.
ticketsPerBlock := dcrutil.Amount(g.params.TicketsPerBlock)
return (powSubsidy * dcrutil.Amount(numVotes)) / ticketsPerBlock
}
// calcPoSSubsidy returns the proof-of-stake subsidy portion for a given block
// height being voted on.
//
// NOTE: This and the other subsidy calculation funcs intentionally are not
// using the blockchain code since the intent is to be able to generate known
// good tests which exercise that code, so it wouldn't make sense to use the
// same code to generate them.
func (g *Generator) calcPoSSubsidy(heightVotedOn uint32) dcrutil.Amount {
if int64(heightVotedOn+1) < g.params.StakeValidationHeight {
return 0
}
fullSubsidy := g.calcFullSubsidy(heightVotedOn)
posProportion := dcrutil.Amount(g.params.StakeRewardProportion)
totalProportions := dcrutil.Amount(g.params.TotalSubsidyProportions())
return (fullSubsidy * posProportion) / totalProportions
}
// calcDevSubsidy returns the dev org subsidy portion from a given full subsidy.
//
// NOTE: This and the other subsidy calculation funcs intentionally are not
// using the blockchain code since the intent is to be able to generate known
// good tests which exercise that code, so it wouldn't make sense to use the
// same code to generate them.
func (g *Generator) calcDevSubsidy(fullSubsidy dcrutil.Amount, blockHeight uint32, numVotes uint16) dcrutil.Amount {
devProportion := dcrutil.Amount(g.params.BlockTaxProportion)
totalProportions := dcrutil.Amount(g.params.TotalSubsidyProportions())
devSubsidy := (fullSubsidy * devProportion) / totalProportions
if int64(blockHeight) < g.params.StakeValidationHeight {
return devSubsidy
}
// Reduce the subsidy according to the number of votes.
ticketsPerBlock := dcrutil.Amount(g.params.TicketsPerBlock)
return (devSubsidy * dcrutil.Amount(numVotes)) / ticketsPerBlock
}
// standardCoinbaseOpReturnScript returns a standard script suitable for use as
// the second output of a standard coinbase transaction of a new block. In
// particular, the serialized data used with the OP_RETURN starts with the block
// height and is followed by 32 bytes which are treated as 4 uint64 extra
// nonces. This implementation puts a cryptographically random value into the
// final extra nonce position. The actual format of the data after the block
// height is not defined however this effectivley mirrors the actual mining code
// at the time it was written.
func standardCoinbaseOpReturnScript(blockHeight uint32) []byte {
rand, err := wire.RandomUint64()
if err != nil {
panic(err)
}
data := make([]byte, 36, 36)
binary.LittleEndian.PutUint32(data[0:4], blockHeight)
binary.LittleEndian.PutUint64(data[28:36], rand)
return opReturnScript(data)
}
// addCoinbaseTxOutputs adds the following outputs to the provided transaction
// which is assumed to be a coinbase transaction:
// - First output pays the development subsidy portion to the dev org
// - Second output is a standard provably prunable data-only coinbase output
// - Third and subsequent outputs pay the pow subsidy portion to the generic
// OP_TRUE p2sh script hash
func (g *Generator) addCoinbaseTxOutputs(tx *wire.MsgTx, blockHeight uint32, devSubsidy, powSubsidy dcrutil.Amount) {
// First output is the developer subsidy.
tx.AddTxOut(&wire.TxOut{
Value: int64(devSubsidy),
Version: g.params.OrganizationPkScriptVersion,
PkScript: g.params.OrganizationPkScript,
})
// Second output is a provably prunable data-only output that is used
// to ensure the coinbase is unique.
tx.AddTxOut(wire.NewTxOut(0, standardCoinbaseOpReturnScript(blockHeight)))
// Final outputs are the proof-of-work subsidy split into more than one
// output. These are in turn used througout the tests as inputs to
// other transactions such as ticket purchases and additional spend
// transactions.
const numPoWOutputs = 6
amount := powSubsidy / numPoWOutputs
for i := 0; i < numPoWOutputs; i++ {
if i == numPoWOutputs-1 {
amount = powSubsidy - amount*(numPoWOutputs-1)
}
tx.AddTxOut(wire.NewTxOut(int64(amount), g.p2shOpTrueScript))
}
}
// CreateCoinbaseTx returns a coinbase transaction paying an appropriate
// subsidy based on the passed block height and number of votes to the dev org
// and proof-of-work miner.
//
// See the addCoinbaseTxOutputs documentation for a breakdown of the outputs
// the transaction contains.
func (g *Generator) CreateCoinbaseTx(blockHeight uint32, numVotes uint16) *wire.MsgTx {
// Calculate the subsidy proportions based on the block height and the
// number of votes the block will include.
fullSubsidy := g.calcFullSubsidy(blockHeight)
devSubsidy := g.calcDevSubsidy(fullSubsidy, blockHeight, numVotes)
powSubsidy := g.calcPoWSubsidy(fullSubsidy, blockHeight, numVotes)
tx := wire.NewMsgTx()
tx.AddTxIn(&wire.TxIn{
// Coinbase transactions have no inputs, so previous outpoint is
// zero hash and max index.
PreviousOutPoint: *wire.NewOutPoint(&chainhash.Hash{},
wire.MaxPrevOutIndex, wire.TxTreeRegular),
Sequence: wire.MaxTxInSequenceNum,
ValueIn: int64(devSubsidy + powSubsidy),
BlockHeight: wire.NullBlockHeight,
BlockIndex: wire.NullBlockIndex,
SignatureScript: coinbaseSigScript,
})
g.addCoinbaseTxOutputs(tx, blockHeight, devSubsidy, powSubsidy)
return tx
}
// purchaseCommitmentScript returns a standard provably-pruneable OP_RETURN
// commitment script suitable for use in a ticket purchase tx (sstx) using the
// provided target address, amount, and fee limits.
func purchaseCommitmentScript(addr dcrutil.Address, amount, voteFeeLimit, revocationFeeLimit dcrutil.Amount) []byte {
// The limits are defined in terms of the closest base 2 exponent and
// a bit that must be set to specify the limit is to be applied. The
// vote fee exponent is in the bottom 8 bits, while the revocation fee
// exponent is in the upper 8 bits.
limits := uint16(0)
if voteFeeLimit != 0 {
exp := uint16(math.Ceil(math.Log2(float64(voteFeeLimit))))
limits |= (exp | 0x40)
}
if revocationFeeLimit != 0 {
exp := uint16(math.Ceil(math.Log2(float64(revocationFeeLimit))))
limits |= ((exp | 0x40) << 8)
}
// The data consists of the 20-byte raw script address for the given
// address, 8 bytes for the amount to commit to (with the upper bit flag
// set to indicate a pay-to-script-hash address), and 2 bytes for the
// fee limits.
var data [30]byte
copy(data[:], addr.ScriptAddress())
binary.LittleEndian.PutUint64(data[20:], uint64(amount))
data[27] |= 1 << 7
binary.LittleEndian.PutUint16(data[28:], limits)
script, err := txscript.NewScriptBuilder().AddOp(txscript.OP_RETURN).
AddData(data[:]).Script()
if err != nil {
panic(err)
}
return script
}
// createTicketPurchaseTx creates a new transaction that spends the provided
// output to purchase a stake submission ticket (sstx) at the given ticket
// price. Both the ticket and the change will go to a p2sh script that is
// composed with a single OP_TRUE.
//
// The transaction consists of the following outputs:
// - First output is an OP_SSTX followed by the OP_TRUE p2sh script hash
// - Second output is an OP_RETURN followed by the commitment script
// - Third output is an OP_SSTXCHANGE followed by the OP_TRUE p2sh script hash
func (g *Generator) createTicketPurchaseTx(spend *SpendableOut, ticketPrice, fee dcrutil.Amount) *wire.MsgTx {
// The first output is the voting rights address. This impl uses the
// standard pay-to-script-hash to an OP_TRUE.
pkScript, err := txscript.PayToSStx(g.p2shOpTrueAddr)
if err != nil {
panic(err)
}
// Generate the commitment script.
commitScript := purchaseCommitmentScript(g.p2shOpTrueAddr,
ticketPrice+fee, 0, ticketPrice)
// Calculate change and generate script to deliver it.
change := spend.amount - ticketPrice - fee
changeScript, err := txscript.PayToSStxChange(g.p2shOpTrueAddr)
if err != nil {
panic(err)
}
// Generate and return the transaction spending from the provided
// spendable output with the previously described outputs.
tx := wire.NewMsgTx()
tx.AddTxIn(&wire.TxIn{
PreviousOutPoint: spend.prevOut,
Sequence: wire.MaxTxInSequenceNum,
ValueIn: int64(spend.amount),
BlockHeight: spend.blockHeight,
BlockIndex: spend.blockIndex,
SignatureScript: opTrueRedeemScript,
})
tx.AddTxOut(wire.NewTxOut(int64(ticketPrice), pkScript))
tx.AddTxOut(wire.NewTxOut(0, commitScript))
tx.AddTxOut(wire.NewTxOut(int64(change), changeScript))
return tx
}
// isTicketPurchaseTx returns whether or not the passed transaction is a stake
// ticket purchase.
//
// NOTE: Like many other functions in this test code, this function
// intentionally does not use the blockchain/stake package code since the intent
// is to be able to generate known good tests which exercise that code, so it
// wouldn't make sense to use the same code to generate them. It must also be
// noted that this function is NOT robust. It is the minimum necessary needed
// by the testing framework.
func isTicketPurchaseTx(tx *wire.MsgTx) bool {
if len(tx.TxOut) == 0 {
return false
}
txOut := tx.TxOut[0]
scriptClass := txscript.GetScriptClass(txOut.Version, txOut.PkScript)
return scriptClass == txscript.StakeSubmissionTy
}
// isVoteTx returns whether or not the passed tx is a stake vote (ssgen).
//
// NOTE: Like many other functions in this test code, this function
// intentionally does not use the blockchain/stake package code since the intent
// is to be able to generate known good tests which exercise that code, so it
// wouldn't make sense to use the same code to generate them. It must also be
// noted that this function is NOT robust. It is the minimum necessary needed
// by the testing framework.
func isVoteTx(tx *wire.MsgTx) bool {
if len(tx.TxOut) < 3 {
return false
}
txOut := tx.TxOut[2]
scriptClass := txscript.GetScriptClass(txOut.Version, txOut.PkScript)
return scriptClass == txscript.StakeGenTy
}
// isRevocationTx returns whether or not the passed tx is a stake ticket
// revocation (ssrtx).
//
// NOTE: Like many other functions in this test code, this function
// intentionally does not use the blockchain/stake package code since the intent
// is to be able to generate known good tests which exercise that code, so it
// wouldn't make sense to use the same code to generate them. It must also be
// noted that this function is NOT robust. It is the minimum necessary needed
// by the testing framework.
func isRevocationTx(tx *wire.MsgTx) bool {
if len(tx.TxOut) == 0 {
return false
}
txOut := tx.TxOut[0]
scriptClass := txscript.GetScriptClass(txOut.Version, txOut.PkScript)
return scriptClass == txscript.StakeRevocationTy
}
// voteBlockScript returns a standard provably-pruneable OP_RETURN script
// suitable for use in a vote tx (ssgen) given the block to vote on.
func voteBlockScript(parentBlock *wire.MsgBlock) []byte {
var data [36]byte
parentHash := parentBlock.BlockHash()
copy(data[:], parentHash[:])
binary.LittleEndian.PutUint32(data[32:], parentBlock.Header.Height)
script, err := txscript.NewScriptBuilder().AddOp(txscript.OP_RETURN).
AddData(data[:]).Script()
if err != nil {
panic(err)
}
return script
}
// voteBitsScript returns a standard provably-pruneable OP_RETURN script
// suitable for use in a vote tx (ssgen) with the appropriate vote bits set
// depending on the provided params.
func voteBitsScript(bits uint16, voteVersion uint32) []byte {
data := make([]byte, 6)
binary.LittleEndian.PutUint16(data[:], bits)
binary.LittleEndian.PutUint32(data[2:], voteVersion)
if voteVersion == 0 {
data = data[:2]
}
script, err := txscript.NewScriptBuilder().AddOp(txscript.OP_RETURN).
AddData(data[:]).Script()
if err != nil {
panic(err)
}
return script
}
// createVoteTx returns a new transaction (ssgen) paying an appropriate subsidy
// for the given block height (and the number of votes per block) as well as the
// original commitments.
//
// The transaction consists of the following outputs:
// - First output is an OP_RETURN followed by the block hash and height
// - Second output is an OP_RETURN followed by the vote bits
// - Third and subsequent outputs are the payouts according to the ticket
// commitments and the appropriate proportion of the vote subsidy.
func (g *Generator) createVoteTx(parentBlock *wire.MsgBlock, ticket *stakeTicket) *wire.MsgTx {
// Calculate the proof-of-stake subsidy proportion based on the block
// height.
posSubsidy := g.calcPoSSubsidy(parentBlock.Header.Height)
voteSubsidy := posSubsidy / dcrutil.Amount(g.params.TicketsPerBlock)
ticketPrice := dcrutil.Amount(ticket.tx.TxOut[0].Value)
// The first output is the block (hash and height) the vote is for.
blockScript := voteBlockScript(parentBlock)
// The second output is the vote bits.
voteScript := voteBitsScript(voteBitYes, 0)
// The third and subsequent outputs pay the original commitment amounts
// along with the appropriate portion of the vote subsidy. This impl
// uses the standard pay-to-script-hash to an OP_TRUE.
stakeGenScript, err := txscript.PayToSSGen(g.p2shOpTrueAddr)
if err != nil {
panic(err)
}
// Generate and return the transaction with the proof-of-stake subsidy
// coinbase and spending from the provided ticket along with the
// previously described outputs.
ticketHash := ticket.tx.CachedTxHash()
tx := wire.NewMsgTx()
tx.AddTxIn(&wire.TxIn{
PreviousOutPoint: *wire.NewOutPoint(&chainhash.Hash{},
wire.MaxPrevOutIndex, wire.TxTreeRegular),
Sequence: wire.MaxTxInSequenceNum,
ValueIn: int64(voteSubsidy),
BlockHeight: wire.NullBlockHeight,
BlockIndex: wire.NullBlockIndex,
SignatureScript: g.params.StakeBaseSigScript,
})
tx.AddTxIn(&wire.TxIn{
PreviousOutPoint: *wire.NewOutPoint(ticketHash, 0,
wire.TxTreeStake),
Sequence: wire.MaxTxInSequenceNum,
ValueIn: int64(ticketPrice),
BlockHeight: ticket.blockHeight,
BlockIndex: ticket.blockIndex,
SignatureScript: opTrueRedeemScript,
})
tx.AddTxOut(wire.NewTxOut(0, blockScript))
tx.AddTxOut(wire.NewTxOut(0, voteScript))
tx.AddTxOut(wire.NewTxOut(int64(voteSubsidy+ticketPrice), stakeGenScript))
return tx
}
// ancestorBlock returns the ancestor block at the provided height by following
// the chain backwards from the given block. The returned block will be nil
// when a height is requested that is after the height of the passed block.
// Also, a callback can optionally be provided that is invoked with each block
// as it traverses.
func (g *Generator) ancestorBlock(block *wire.MsgBlock, height uint32, f func(*wire.MsgBlock)) *wire.MsgBlock {
// Nothing to do if the requested height is outside of the valid
// range.
if block == nil || height > block.Header.Height {
return nil
}
// Iterate backwards until the requested height is reached.
for block != nil && block.Header.Height > height {
block = g.blocks[block.Header.PrevBlock]
if f != nil && block != nil {
f(block)
}
}
return block
}
// mergeDifficulty takes an original stake difficulty and two new, scaled
// stake difficulties, merges the new difficulties, and outputs a new
// merged stake difficulty.
func mergeDifficulty(oldDiff int64, newDiff1 int64, newDiff2 int64) int64 {
newDiff1Big := big.NewInt(newDiff1)
newDiff2Big := big.NewInt(newDiff2)
newDiff2Big.Lsh(newDiff2Big, 32)
oldDiffBig := big.NewInt(oldDiff)
oldDiffBigLSH := big.NewInt(oldDiff)
oldDiffBigLSH.Lsh(oldDiffBig, 32)
newDiff1Big.Div(oldDiffBigLSH, newDiff1Big)
newDiff2Big.Div(newDiff2Big, oldDiffBig)
// Combine the two changes in difficulty.
summedChange := big.NewInt(0)
summedChange.Set(newDiff2Big)
summedChange.Lsh(summedChange, 32)
summedChange.Div(summedChange, newDiff1Big)
summedChange.Mul(summedChange, oldDiffBig)
summedChange.Rsh(summedChange, 32)
return summedChange.Int64()
}
// limitRetarget clamps the passed new difficulty to the old one adjusted by the
// factor specified in the chain parameters. This ensures the difficulty can
// only move up or down by a limited amount.
func (g *Generator) limitRetarget(oldDiff, newDiff int64) int64 {
maxRetarget := g.params.RetargetAdjustmentFactor
switch {
case newDiff == 0:
fallthrough
case (oldDiff / newDiff) > (maxRetarget - 1):
return oldDiff / maxRetarget
case (newDiff / oldDiff) > (maxRetarget - 1):
return oldDiff * maxRetarget
}
return newDiff
}
// calcNextRequiredDifficulty returns the required proof-of-work difficulty for
// the block after the current tip block the generator is associated with.
//
// An overview of the algorithm is as follows:
// 1) Use the proof-of-work limit for all blocks before the first retarget
// window
// 2) Use the previous block's difficulty if the next block is not at a retarget
// interval
// 3) Calculate the ideal retarget difficulty for each window based on the
// actual timespan of the window versus the target timespan and exponentially
// weight each difficulty such that the most recent window has the highest
// weight
// 4) Calculate the final retarget difficulty based on the exponential weighted
// average and ensure it is limited to the max retarget adjustment factor
func (g *Generator) calcNextRequiredDifficulty() uint32 {
// Target difficulty before the first retarget interval is the pow
// limit.
nextHeight := g.tip.Header.Height + 1
windowSize := g.params.WorkDiffWindowSize
if int64(nextHeight) < windowSize {
return g.params.PowLimitBits
}
// Return the previous block's difficulty requirements if the next block
// is not at a difficulty retarget interval.
curDiff := int64(g.tip.Header.Bits)
if int64(nextHeight)%windowSize != 0 {
return uint32(curDiff)
}
// Calculate the ideal retarget difficulty for each window based on the
// actual time between blocks versus the target time and exponentially
// weight them.
adjustedTimespan := big.NewInt(0)
tempBig := big.NewInt(0)
weightedTimespanSum, weightSum := big.NewInt(0), big.NewInt(0)
targetTimespan := int64(g.params.TargetTimespan)
targetTimespanBig := big.NewInt(targetTimespan)
numWindows := g.params.WorkDiffWindows
weightAlpha := g.params.WorkDiffAlpha
block := g.tip
finalWindowTime := block.Header.Timestamp.UnixNano()
for i := int64(0); i < numWindows; i++ {
// Get the timestamp of the block at the start of the window and
// calculate the actual timespan accordingly. Use the target
// timespan if there are not yet enough blocks left to cover the
// window.
actualTimespan := targetTimespan
if int64(block.Header.Height) > windowSize {
for j := int64(0); j < windowSize; j++ {
block = g.blocks[block.Header.PrevBlock]
}
startWindowTime := block.Header.Timestamp.UnixNano()
actualTimespan = finalWindowTime - startWindowTime
// Set final window time for the next window.
finalWindowTime = startWindowTime
}
// Calculate the ideal retarget difficulty for the window based
// on the actual timespan and weight it exponentially by
// multiplying it by 2^(window_number) such that the most recent
// window receives the most weight.
//
// Also, since integer division is being used, shift up the
// number of new tickets 32 bits to avoid losing precision.
//
// windowWeightShift = ((numWindows - i) * weightAlpha)
// adjustedTimespan = (actualTimespan << 32) / targetTimespan
// weightedTimespanSum += adjustedTimespan << windowWeightShift
// weightSum += 1 << windowWeightShift
windowWeightShift := uint((numWindows - i) * weightAlpha)
adjustedTimespan.SetInt64(actualTimespan)
adjustedTimespan.Lsh(adjustedTimespan, 32)
adjustedTimespan.Div(adjustedTimespan, targetTimespanBig)
adjustedTimespan.Lsh(adjustedTimespan, windowWeightShift)
weightedTimespanSum.Add(weightedTimespanSum, adjustedTimespan)
weight := tempBig.SetInt64(1)
weight.Lsh(weight, windowWeightShift)
weightSum.Add(weightSum, weight)
}
// Calculate the retarget difficulty based on the exponential weigthed
// average and shift the result back down 32 bits to account for the
// previous shift up in order to avoid losing precision. Then, limit it
// to the maximum allowed retarget adjustment factor.
//
// nextDiff = (weightedTimespanSum/weightSum * curDiff) >> 32
curDiffBig := tempBig.SetInt64(curDiff)
weightedTimespanSum.Div(weightedTimespanSum, weightSum)
weightedTimespanSum.Mul(weightedTimespanSum, curDiffBig)
weightedTimespanSum.Rsh(weightedTimespanSum, 32)
nextDiff := weightedTimespanSum.Int64()
nextDiff = g.limitRetarget(curDiff, nextDiff)
if nextDiff > int64(g.params.PowLimitBits) {
return g.params.PowLimitBits
}
return uint32(nextDiff)
}
// calcNextRequiredStakeDifficulty returns the required stake difficulty (aka
// ticket price) for the block after the current tip block the generator is
// associated with.
//
// An overview of the algorithm is as follows:
// 1) Use the minimum value for any blocks before any tickets could have
// possibly been purchased due to coinbase maturity requirements
// 2) Return 0 if the current tip block stake difficulty is 0. This is a
// safety check against a condition that should never actually happen.
// 3) Use the previous block's difficulty if the next block is not at a retarget
// interval
// 4) Calculate the ideal retarget difficulty for each window based on the
// actual pool size in the window versus the target pool size skewed by a
// constant factor to weight the ticket pool size instead of the tickets per
// block and exponentially weight each difficulty such that the most recent
// window has the highest weight
// 5) Calculate the pool size retarget difficulty based on the exponential
// weighted average and ensure it is limited to the max retarget adjustment
// factor -- This is the first metric used to calculate the final difficulty
// 6) Calculate the ideal retarget difficulty for each window based on the
// actual new tickets in the window versus the target new tickets per window
// and exponentially weight each difficulty such that the most recent window
// has the highest weight
// 7) Calculate the tickets per window retarget difficulty based on the
// exponential weighted average and ensure it is limited to the max retarget
// adjustment factor
// 8) Calculate the final difficulty by averaging the pool size retarget
// difficulty from #5 and the tickets per window retarget difficulty from #7
// using scaled multiplication and ensure it is limited to the max retarget
// adjustment factor
//
// NOTE: In order to simplify the test code, this implementation does not use
// big integers so it will NOT match the actual consensus code for really big
// numbers. However, the parameters on simnet and the pool sizes used in these
// tests are low enough that this is not an issue for the tests. Anyone looking
// at this code should NOT use it for mainnet calculations as is since it will
// not always yield the correct results.
func (g *Generator) calcNextRequiredStakeDifficulty() int64 {
// Stake difficulty before any tickets could possibly be purchased is
// the minimum value.
nextHeight := g.tip.Header.Height + 1
stakeDiffStartHeight := uint32(g.params.CoinbaseMaturity) + 1
if nextHeight < stakeDiffStartHeight {
return g.params.MinimumStakeDiff
}
// Return 0 if the current difficulty is already zero since any scaling
// of 0 is still 0. This should never really happen since there is a
// minimum stake difficulty, but the consensus code checks the condition
// just in case, so follow suit here.
curDiff := g.tip.Header.SBits
if curDiff == 0 {
return 0
}
// Return the previous block's difficulty requirements if the next block
// is not at a difficulty retarget interval.
windowSize := g.params.StakeDiffWindowSize
if int64(nextHeight)%windowSize != 0 {
return curDiff
}
// --------------------------------
// Ideal pool size retarget metric.
// --------------------------------
// Calculate the ideal retarget difficulty for each window based on the
// actual pool size in the window versus the target pool size and
// exponentially weight them.
var weightedPoolSizeSum, weightSum uint64
ticketsPerBlock := int64(g.params.TicketsPerBlock)
targetPoolSize := ticketsPerBlock * int64(g.params.TicketPoolSize)
numWindows := g.params.StakeDiffWindows
weightAlpha := g.params.StakeDiffAlpha
block := g.tip
for i := int64(0); i < numWindows; i++ {
// Get the pool size for the block at the start of the window.
// Use zero if there are not yet enough blocks left to cover the
// window.
prevRetargetHeight := nextHeight - uint32(windowSize*(i+1))
windowPoolSize := int64(0)
block = g.ancestorBlock(block, prevRetargetHeight, nil)
if block != nil {
windowPoolSize = int64(block.Header.PoolSize)
}
// Skew the pool size by the constant weight factor specified in
// the chain parameters (which is typically the max adjustment
// factor) in order to help weight the ticket pool size versus
// tickets per block. Also, ensure the skewed pool size is a
// minimum of 1.
skewedPoolSize := targetPoolSize + (windowPoolSize-
targetPoolSize)*int64(g.params.TicketPoolSizeWeight)
if skewedPoolSize <= 0 {
skewedPoolSize = 1
}
// Calculate the ideal retarget difficulty for the window based
// on the skewed pool size and weight it exponentially by
// multiplying it by 2^(window_number) such that the most recent
// window receives the most weight.
//
// Also, since integer division is being used, shift up the
// number of new tickets 32 bits to avoid losing precision.
//
// NOTE: The real algorithm uses big ints, but these purpose
// built tests won't be using large enough values to overflow,
// so just use uint64s.
adjusted := (skewedPoolSize << 32) / targetPoolSize
adjusted = adjusted << uint64((numWindows-i)*weightAlpha)
weightedPoolSizeSum += uint64(adjusted)
weightSum += 1 << uint64((numWindows-i)*weightAlpha)
}
// Calculate the pool size retarget difficulty based on the exponential
// weigthed average and shift the result back down 32 bits to account
// for the previous shift up in order to avoid losing precision. Then,
// limit it to the maximum allowed retarget adjustment factor.
//
// This is the first metric used in the final calculated difficulty.
nextPoolSizeDiff := (int64(weightedPoolSizeSum/weightSum) * curDiff) >> 32
nextPoolSizeDiff = g.limitRetarget(curDiff, nextPoolSizeDiff)
// -----------------------------------------
// Ideal tickets per window retarget metric.
// -----------------------------------------
// Calculate the ideal retarget difficulty for each window based on the
// actual number of new tickets in the window versus the target tickets
// per window and exponentially weight them.
var weightedTicketsSum uint64
targetTicketsPerWindow := ticketsPerBlock * windowSize
block = g.tip
for i := int64(0); i < numWindows; i++ {
// Since the difficulty for the next block after the current tip
// is being calculated and there is no such block yet, the sum
// of all new tickets in the first window needs to start with
// the number of new tickets in the tip block.
var windowNewTickets int64
if i == 0 {
windowNewTickets = int64(block.Header.FreshStake)
}
// Tally all of the new tickets in all blocks in the window and
// ensure the number of new tickets is a minimum of 1.
prevRetargetHeight := nextHeight - uint32(windowSize*(i+1))
block = g.ancestorBlock(block, prevRetargetHeight, func(blk *wire.MsgBlock) {
windowNewTickets += int64(blk.Header.FreshStake)
})
if windowNewTickets <= 0 {
windowNewTickets = 1
}
// Calculate the ideal retarget difficulty for the window based
// on the number of new tickets and weight it exponentially by
// multiplying it by 2^(window_number) such that the most recent
// window receives the most weight.
//
// Also, since integer division is being used, shift up the
// number of new tickets 32 bits to avoid losing precision.
//
// NOTE: The real algorithm uses big ints, but these purpose
// built tests won't be using large enough values to overflow,
// so just use uint64s.
adjusted := (windowNewTickets << 32) / targetTicketsPerWindow
adjusted = adjusted << uint64((numWindows-i)*weightAlpha)
weightedTicketsSum += uint64(adjusted)
}
// Calculate the tickets per window retarget difficulty based on the
// exponential weighted average and shift the result back down 32 bits
// to account for the previous shift up in order to avoid losing
// precision. Then, limit it to the maximum allowed retarget adjustment
// factor.
//
// This is the second metric used in the final calculated difficulty.
nextNewTixDiff := (int64(weightedTicketsSum/weightSum) * curDiff) >> 32
nextNewTixDiff = g.limitRetarget(curDiff, nextNewTixDiff)
// Average the previous two metrics using scaled multiplication and
// ensure the result is limited to both the maximum allowed retarget
// adjustment factor and the minimum allowed stake difficulty.
nextDiff := mergeDifficulty(curDiff, nextPoolSizeDiff, nextNewTixDiff)
nextDiff = g.limitRetarget(curDiff, nextDiff)
if nextDiff < g.params.MinimumStakeDiff {
return g.params.MinimumStakeDiff
}
return nextDiff
}
// hash256prng is a determinstic pseudorandom number generator that uses a
// 256-bit secure hashing function to generate random uint32s starting from
// an initial seed.
type hash256prng struct {
seed chainhash.Hash // Initialization seed
idx uint64 // Hash iterator index
cachedHash chainhash.Hash // Most recently generated hash
hashOffset int // Offset into most recently generated hash
}
// newHash256PRNG creates a pointer to a newly created hash256PRNG.
func newHash256PRNG(seed []byte) *hash256prng {
// The provided seed is initialized by appending a constant derived from
// the hex representation of pi and hashing the result to give 32 bytes.
// This ensures the PRNG is always doing a short number of rounds