github.com/energicryptocurrency/go-energi@v1.1.7/core/evm.go (about) 1 // Copyright 2018 The Energi Core Authors 2 // Copyright 2016 The go-ethereum Authors 3 // This file is part of the Energi Core library. 4 // 5 // The Energi Core library is free software: you can redistribute it and/or modify 6 // it under the terms of the GNU Lesser General Public License as published by 7 // the Free Software Foundation, either version 3 of the License, or 8 // (at your option) any later version. 9 // 10 // The Energi Core library is distributed in the hope that it will be useful, 11 // but WITHOUT ANY WARRANTY; without even the implied warranty of 12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 // GNU Lesser General Public License for more details. 14 // 15 // You should have received a copy of the GNU Lesser General Public License 16 // along with the Energi Core library. If not, see <http://www.gnu.org/licenses/>. 17 18 package core 19 20 import ( 21 "math/big" 22 23 "github.com/energicryptocurrency/go-energi/common" 24 "github.com/energicryptocurrency/go-energi/consensus" 25 "github.com/energicryptocurrency/go-energi/core/types" 26 "github.com/energicryptocurrency/go-energi/core/vm" 27 ) 28 29 // ChainContext supports retrieving headers and consensus parameters from the 30 // current blockchain to be used during transaction processing. 31 type ChainContext interface { 32 // Engine retrieves the chain's consensus engine. 33 Engine() consensus.Engine 34 35 // GetHeader returns the hash corresponding to their hash. 36 GetHeader(common.Hash, uint64) *types.Header 37 } 38 39 // NewEVMContext creates a new context for use in the EVM. 40 func NewEVMContext(msg Message, header *types.Header, chain ChainContext, author *common.Address) vm.Context { 41 // If we don't have an explicit author (i.e. not mining), extract from the header 42 var beneficiary common.Address 43 if author == nil { 44 beneficiary, _ = chain.Engine().Author(header) // Ignore error, we're past header validation 45 } else { 46 beneficiary = *author 47 } 48 return vm.Context{ 49 CanTransfer: CanTransfer, 50 Transfer: Transfer, 51 GetHash: GetHashFn(header, chain), 52 Origin: msg.From(), 53 Coinbase: beneficiary, 54 BlockNumber: new(big.Int).Set(header.Number), 55 Time: new(big.Int).SetUint64(header.Time), 56 Difficulty: new(big.Int).Set(header.Difficulty), 57 GasLimit: header.GasLimit, 58 GasPrice: new(big.Int).Set(msg.GasPrice()), 59 } 60 } 61 62 // GetHashFn returns a GetHashFunc which retrieves header hashes by number 63 func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash { 64 var cache map[uint64]common.Hash 65 66 return func(n uint64) common.Hash { 67 // If there's no hash cache yet, make one 68 if cache == nil { 69 cache = map[uint64]common.Hash{ 70 ref.Number.Uint64() - 1: ref.ParentHash, 71 } 72 } 73 // Try to fulfill the request from the cache 74 if hash, ok := cache[n]; ok { 75 return hash 76 } 77 // Not cached, iterate the blocks and cache the hashes 78 for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) { 79 cache[header.Number.Uint64()-1] = header.ParentHash 80 if n == header.Number.Uint64()-1 { 81 return header.ParentHash 82 } 83 } 84 return common.Hash{} 85 } 86 } 87 88 // CanTransfer checks whether there are enough funds in the address' account to make a transfer. 89 // This does not take the necessary gas in to account to make the transfer valid. 90 func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool { 91 if amount.Cmp(common.Big0) != 0 && IsBlacklisted(db, addr) { 92 return false 93 } 94 95 return db.GetBalance(addr).Cmp(amount) >= 0 96 } 97 98 // Transfer subtracts amount from sender and adds amount to recipient using the given Db 99 func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) { 100 db.SubBalance(sender, amount) 101 db.AddBalance(recipient, amount) 102 }