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// Copyright 2015 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 gasprice
import (
"math/big"
"math/rand"
"sync"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
)
const (
gpoProcessPastBlocks = 100
// for testing
gpoDefaultBaseCorrectionFactor = 110
gpoDefaultMinGasPrice = 10000000000000
)
type blockPriceInfo struct {
baseGasPrice *big.Int
}
type GpoParams struct {
GpoMinGasPrice *big.Int
GpoMaxGasPrice *big.Int
GpoFullBlockRatio int
GpobaseStepDown int
GpobaseStepUp int
GpobaseCorrectionFactor int
}
// GasPriceOracle recommends gas prices based on the content of recent
// blocks.
type GasPriceOracle struct {
chain *core.BlockChain
db ethdb.Database
evmux *event.TypeMux
params *GpoParams
initOnce sync.Once
minPrice *big.Int
lastBaseMutex sync.Mutex
lastBase *big.Int
// state of listenLoop
blocks map[uint64]*blockPriceInfo
firstProcessed, lastProcessed uint64
minBase *big.Int
}
// NewGasPriceOracle returns a new oracle.
func NewGasPriceOracle(chain *core.BlockChain, db ethdb.Database, evmux *event.TypeMux, params *GpoParams) *GasPriceOracle {
minprice := params.GpoMinGasPrice
if minprice == nil {
minprice = big.NewInt(gpoDefaultMinGasPrice)
}
minbase := new(big.Int).Mul(minprice, big.NewInt(100))
if params.GpobaseCorrectionFactor > 0 {
minbase = minbase.Div(minbase, big.NewInt(int64(params.GpobaseCorrectionFactor)))
}
return &GasPriceOracle{
chain: chain,
db: db,
evmux: evmux,
params: params,
blocks: make(map[uint64]*blockPriceInfo),
minBase: minbase,
minPrice: minprice,
lastBase: minprice,
}
}
func (gpo *GasPriceOracle) init() {
gpo.initOnce.Do(func() {
gpo.processPastBlocks()
go gpo.listenLoop()
})
}
func (self *GasPriceOracle) processPastBlocks() {
last := int64(-1)
cblock := self.chain.CurrentBlock()
if cblock != nil {
last = int64(cblock.NumberU64())
}
first := int64(0)
if last > gpoProcessPastBlocks {
first = last - gpoProcessPastBlocks
}
self.firstProcessed = uint64(first)
for i := first; i <= last; i++ {
block := self.chain.GetBlockByNumber(uint64(i))
if block != nil {
self.processBlock(block)
}
}
}
func (self *GasPriceOracle) listenLoop() {
events := self.evmux.Subscribe(core.ChainEvent{}, core.ChainSplitEvent{})
defer events.Unsubscribe()
for event := range events.Chan() {
switch event := event.Data.(type) {
case core.ChainEvent:
self.processBlock(event.Block)
case core.ChainSplitEvent:
self.processBlock(event.Block)
}
}
}
func (self *GasPriceOracle) processBlock(block *types.Block) {
i := block.NumberU64()
if i > self.lastProcessed {
self.lastProcessed = i
}
lastBase := self.minPrice
bpl := self.blocks[i-1]
if bpl != nil {
lastBase = bpl.baseGasPrice
}
if lastBase == nil {
return
}
var corr int
lp := self.lowestPrice(block)
if lp == nil {
return
}
if lastBase.Cmp(lp) < 0 {
corr = self.params.GpobaseStepUp
} else {
corr = -self.params.GpobaseStepDown
}
crand := int64(corr * (900 + rand.Intn(201)))
newBase := new(big.Int).Mul(lastBase, big.NewInt(1000000+crand))
newBase.Div(newBase, big.NewInt(1000000))
if newBase.Cmp(self.minBase) < 0 {
newBase = self.minBase
}
bpi := self.blocks[i]
if bpi == nil {
bpi = &blockPriceInfo{}
self.blocks[i] = bpi
}
bpi.baseGasPrice = newBase
self.lastBaseMutex.Lock()
self.lastBase = newBase
self.lastBaseMutex.Unlock()
log.Trace("Processed block, base price updated", "number", i, "base", newBase)
}
// returns the lowers possible price with which a tx was or could have been included
func (self *GasPriceOracle) lowestPrice(block *types.Block) *big.Int {
gasUsed := big.NewInt(0)
receipts := core.GetBlockReceipts(self.db, block.Hash(), block.NumberU64())
if len(receipts) > 0 {
if cgu := receipts[len(receipts)-1].CumulativeGasUsed; cgu != nil {
gasUsed = receipts[len(receipts)-1].CumulativeGasUsed
}
}
if new(big.Int).Mul(gasUsed, big.NewInt(100)).Cmp(new(big.Int).Mul(block.GasLimit(),
big.NewInt(int64(self.params.GpoFullBlockRatio)))) < 0 {
// block is not full, could have posted a tx with MinGasPrice
return big.NewInt(0)
}
txs := block.Transactions()
if len(txs) == 0 {
return big.NewInt(0)
}
// block is full, find smallest gasPrice
minPrice := txs[0].GasPrice()
for i := 1; i < len(txs); i++ {
price := txs[i].GasPrice()
if price.Cmp(minPrice) < 0 {
minPrice = price
}
}
return minPrice
}
// SuggestPrice returns the recommended gas price.
func (self *GasPriceOracle) SuggestPrice() *big.Int {
self.init()
self.lastBaseMutex.Lock()
price := new(big.Int).Set(self.lastBase)
self.lastBaseMutex.Unlock()
price.Mul(price, big.NewInt(int64(self.params.GpobaseCorrectionFactor)))
price.Div(price, big.NewInt(100))
if price.Cmp(self.minPrice) < 0 {
price.Set(self.minPrice)
} else if self.params.GpoMaxGasPrice != nil && price.Cmp(self.params.GpoMaxGasPrice) > 0 {
price.Set(self.params.GpoMaxGasPrice)
}
return price
}
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