github.com/ethxdao/go-ethereum@v0.0.0-20221218102228-5ae34a9cc189/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/ethxdao/go-ethereum/common"
    23  	"github.com/ethxdao/go-ethereum/consensus"
    24  	"github.com/ethxdao/go-ethereum/core/types"
    25  	"github.com/ethxdao/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 header corresponding to the hash/number argument pair.
    35  	GetHeader(common.Hash, uint64) *types.Header
    36  }
    37  
    38  // NewEVMBlockContext creates a new context for use in the EVM.
    39  func NewEVMBlockContext(header *types.Header, chain ChainContext, author *common.Address) vm.BlockContext {
    40  	var (
    41  		beneficiary common.Address
    42  		baseFee     *big.Int
    43  		random      *common.Hash
    44  	)
    45  
    46  	// If we don't have an explicit author (i.e. not mining), extract from the header
    47  	if author == nil {
    48  		beneficiary, _ = chain.Engine().Author(header) // Ignore error, we're past header validation
    49  	} else {
    50  		beneficiary = *author
    51  	}
    52  	if header.BaseFee != nil {
    53  		baseFee = new(big.Int).Set(header.BaseFee)
    54  	}
    55  	if header.Difficulty.Cmp(common.Big0) == 0 {
    56  		random = &header.MixDigest
    57  	}
    58  	return vm.BlockContext{
    59  		CanTransfer: CanTransfer,
    60  		Transfer:    Transfer,
    61  		GetHash:     GetHashFn(header, chain),
    62  		Coinbase:    beneficiary,
    63  		BlockNumber: new(big.Int).Set(header.Number),
    64  		Time:        new(big.Int).SetUint64(header.Time),
    65  		Difficulty:  new(big.Int).Set(header.Difficulty),
    66  		BaseFee:     baseFee,
    67  		GasLimit:    header.GasLimit,
    68  		Random:      random,
    69  	}
    70  }
    71  
    72  // NewEVMTxContext creates a new transaction context for a single transaction.
    73  func NewEVMTxContext(msg Message) vm.TxContext {
    74  	return vm.TxContext{
    75  		Origin:   msg.From(),
    76  		GasPrice: new(big.Int).Set(msg.GasPrice()),
    77  	}
    78  }
    79  
    80  // GetHashFn returns a GetHashFunc which retrieves header hashes by number
    81  func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
    82  	// Cache will initially contain [refHash.parent],
    83  	// Then fill up with [refHash.p, refHash.pp, refHash.ppp, ...]
    84  	var cache []common.Hash
    85  
    86  	return func(n uint64) common.Hash {
    87  		if ref.Number.Uint64() <= n {
    88  			// This situation can happen if we're doing tracing and using
    89  			// block overrides.
    90  			return common.Hash{}
    91  		}
    92  		// If there's no hash cache yet, make one
    93  		if len(cache) == 0 {
    94  			cache = append(cache, ref.ParentHash)
    95  		}
    96  		if idx := ref.Number.Uint64() - n - 1; idx < uint64(len(cache)) {
    97  			return cache[idx]
    98  		}
    99  		// No luck in the cache, but we can start iterating from the last element we already know
   100  		lastKnownHash := cache[len(cache)-1]
   101  		lastKnownNumber := ref.Number.Uint64() - uint64(len(cache))
   102  
   103  		for {
   104  			header := chain.GetHeader(lastKnownHash, lastKnownNumber)
   105  			if header == nil {
   106  				break
   107  			}
   108  			cache = append(cache, header.ParentHash)
   109  			lastKnownHash = header.ParentHash
   110  			lastKnownNumber = header.Number.Uint64() - 1
   111  			if n == lastKnownNumber {
   112  				return lastKnownHash
   113  			}
   114  		}
   115  		return common.Hash{}
   116  	}
   117  }
   118  
   119  // CanTransfer checks whether there are enough funds in the address' account to make a transfer.
   120  // This does not take the necessary gas in to account to make the transfer valid.
   121  func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {
   122  	return db.GetBalance(addr).Cmp(amount) >= 0
   123  }
   124  
   125  // Transfer subtracts amount from sender and adds amount to recipient using the given Db
   126  func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) {
   127  	db.SubBalance(sender, amount)
   128  	db.AddBalance(recipient, amount)
   129  }