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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 (
"context"
"math/big"
"sort"
"sync"
"github.com/dexon-foundation/dexon/common"
"github.com/dexon-foundation/dexon/core/types"
"github.com/dexon-foundation/dexon/internal/ethapi"
"github.com/dexon-foundation/dexon/params"
"github.com/dexon-foundation/dexon/rpc"
)
var maxPrice = big.NewInt(500 * params.GWei)
type Config struct {
Blocks int
Percentile int
Default *big.Int `toml:",omitempty"`
}
// Oracle recommends gas prices based on the content of recent
// blocks. Suitable for both light and full clients.
type Oracle struct {
backend ethapi.Backend
lastHead common.Hash
lastPrice *big.Int
cacheLock sync.RWMutex
fetchLock sync.Mutex
checkBlocks, maxEmpty, maxBlocks int
percentile int
}
// NewOracle returns a new oracle.
func NewOracle(backend ethapi.Backend, params Config) *Oracle {
blocks := params.Blocks
if blocks < 1 {
blocks = 1
}
percent := params.Percentile
if percent < 0 {
percent = 0
}
if percent > 100 {
percent = 100
}
return &Oracle{
backend: backend,
lastPrice: params.Default,
checkBlocks: blocks,
maxEmpty: blocks / 2,
maxBlocks: blocks * 5,
percentile: percent,
}
}
// SuggestPrice returns the recommended gas price.
func (gpo *Oracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
gpo.cacheLock.RLock()
lastHead := gpo.lastHead
lastPrice := gpo.lastPrice
gpo.cacheLock.RUnlock()
head, _ := gpo.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
headHash := head.Hash()
if headHash == lastHead {
return lastPrice, nil
}
gpo.fetchLock.Lock()
defer gpo.fetchLock.Unlock()
// try checking the cache again, maybe the last fetch fetched what we need
gpo.cacheLock.RLock()
lastHead = gpo.lastHead
lastPrice = gpo.lastPrice
gpo.cacheLock.RUnlock()
if headHash == lastHead {
return lastPrice, nil
}
blockNum := head.Number.Uint64()
ch := make(chan getBlockPricesResult, gpo.checkBlocks)
sent := 0
exp := 0
var blockPrices []*big.Int
for sent < gpo.checkBlocks && blockNum > 0 {
go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.backend.ChainConfig(), big.NewInt(int64(blockNum))), blockNum, ch)
sent++
exp++
blockNum--
}
maxEmpty := gpo.maxEmpty
for exp > 0 {
res := <-ch
if res.err != nil {
return lastPrice, res.err
}
exp--
if res.price != nil {
blockPrices = append(blockPrices, res.price)
continue
}
if maxEmpty > 0 {
maxEmpty--
continue
}
if blockNum > 0 && sent < gpo.maxBlocks {
go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.backend.ChainConfig(), big.NewInt(int64(blockNum))), blockNum, ch)
sent++
exp++
blockNum--
}
}
price := lastPrice
if len(blockPrices) > 0 {
sort.Sort(bigIntArray(blockPrices))
price = blockPrices[(len(blockPrices)-1)*gpo.percentile/100]
}
if price.Cmp(maxPrice) > 0 {
price = new(big.Int).Set(maxPrice)
}
gpo.cacheLock.Lock()
gpo.lastHead = headHash
gpo.lastPrice = price
gpo.cacheLock.Unlock()
return price, nil
}
type getBlockPricesResult struct {
price *big.Int
err error
}
type transactionsByGasPrice []*types.Transaction
func (t transactionsByGasPrice) Len() int { return len(t) }
func (t transactionsByGasPrice) Swap(i, j int) { t[i], t[j] = t[j], t[i] }
func (t transactionsByGasPrice) Less(i, j int) bool { return t[i].GasPrice().Cmp(t[j].GasPrice()) < 0 }
// getBlockPrices calculates the lowest transaction gas price in a given block
// and sends it to the result channel. If the block is empty, price is nil.
func (gpo *Oracle) getBlockPrices(ctx context.Context, signer types.Signer, blockNum uint64, ch chan getBlockPricesResult) {
block, err := gpo.backend.BlockByNumber(ctx, rpc.BlockNumber(blockNum))
if block == nil {
ch <- getBlockPricesResult{nil, err}
return
}
blockTxs := block.Transactions()
txs := make([]*types.Transaction, len(blockTxs))
copy(txs, blockTxs)
sort.Sort(transactionsByGasPrice(txs))
for _, tx := range txs {
sender, err := types.Sender(signer, tx)
if err == nil && sender != block.Coinbase() {
ch <- getBlockPricesResult{tx.GasPrice(), nil}
return
}
}
ch <- getBlockPricesResult{nil, nil}
}
type bigIntArray []*big.Int
func (s bigIntArray) Len() int { return len(s) }
func (s bigIntArray) Less(i, j int) bool { return s[i].Cmp(s[j]) < 0 }
func (s bigIntArray) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
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