github.com/attkernel/go-ethereum@v1.9.7/core/evm.go (about)

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