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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 vm
- import (
- "math/big"
- "github.com/ethereum/go-ethereum/common"
- "github.com/holiman/uint256"
- )
- // ContractRef is a reference to the contract's backing object
- type ContractRef interface {
- Address() common.Address
- }
- // AccountRef implements ContractRef.
- //
- // Account references are used during EVM initialisation and
- // it's primary use is to fetch addresses. Removing this object
- // proves difficult because of the cached jump destinations which
- // are fetched from the parent contract (i.e. the caller), which
- // is a ContractRef.
- type AccountRef common.Address
- // Address casts AccountRef to a Address
- func (ar AccountRef) Address() common.Address { return (common.Address)(ar) }
- // Contract represents an ethereum contract in the state database. It contains
- // the contract code, calling arguments. Contract implements ContractRef
- type Contract struct {
- // CallerAddress is the result of the caller which initialised this
- // contract. However when the "call method" is delegated this value
- // needs to be initialised to that of the caller's caller.
- CallerAddress common.Address
- caller ContractRef
- self ContractRef
- jumpdests map[common.Hash]bitvec // Aggregated result of JUMPDEST analysis.
- analysis bitvec // Locally cached result of JUMPDEST analysis
- Code []byte
- CodeHash common.Hash
- CodeAddr *common.Address
- Input []byte
- Gas uint64
- value *big.Int
- }
- // NewContract returns a new contract environment for the execution of EVM.
- func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uint64) *Contract {
- c := &Contract{CallerAddress: caller.Address(), caller: caller, self: object}
- if parent, ok := caller.(*Contract); ok {
- // Reuse JUMPDEST analysis from parent context if available.
- c.jumpdests = parent.jumpdests
- } else {
- c.jumpdests = make(map[common.Hash]bitvec)
- }
- // Gas should be a pointer so it can safely be reduced through the run
- // This pointer will be off the state transition
- c.Gas = gas
- // ensures a value is set
- c.value = value
- return c
- }
- func (c *Contract) validJumpdest(dest *uint256.Int) bool {
- udest, overflow := dest.Uint64WithOverflow()
- // PC cannot go beyond len(code) and certainly can't be bigger than 63bits.
- // Don't bother checking for JUMPDEST in that case.
- if overflow || udest >= uint64(len(c.Code)) {
- return false
- }
- // Only JUMPDESTs allowed for destinations
- if OpCode(c.Code[udest]) != JUMPDEST {
- return false
- }
- return c.isCode(udest)
- }
- // isCode returns true if the provided PC location is an actual opcode, as
- // opposed to a data-segment following a PUSHN operation.
- func (c *Contract) isCode(udest uint64) bool {
- // Do we already have an analysis laying around?
- if c.analysis != nil {
- return c.analysis.codeSegment(udest)
- }
- // Do we have a contract hash already?
- // If we do have a hash, that means it's a 'regular' contract. For regular
- // contracts ( not temporary initcode), we store the analysis in a map
- if c.CodeHash != (common.Hash{}) {
- // Does parent context have the analysis?
- analysis, exist := c.jumpdests[c.CodeHash]
- if !exist {
- // Do the analysis and save in parent context
- // We do not need to store it in c.analysis
- analysis = codeBitmap(c.Code)
- c.jumpdests[c.CodeHash] = analysis
- }
- // Also stash it in current contract for faster access
- c.analysis = analysis
- return analysis.codeSegment(udest)
- }
- // We don't have the code hash, most likely a piece of initcode not already
- // in state trie. In that case, we do an analysis, and save it locally, so
- // we don't have to recalculate it for every JUMP instruction in the execution
- // However, we don't save it within the parent context
- if c.analysis == nil {
- c.analysis = codeBitmap(c.Code)
- }
- return c.analysis.codeSegment(udest)
- }
- // AsDelegate sets the contract to be a delegate call and returns the current
- // contract (for chaining calls)
- func (c *Contract) AsDelegate() *Contract {
- // NOTE: caller must, at all times be a contract. It should never happen
- // that caller is something other than a Contract.
- parent := c.caller.(*Contract)
- c.CallerAddress = parent.CallerAddress
- c.value = parent.value
- return c
- }
- // GetOp returns the n'th element in the contract's byte array
- func (c *Contract) GetOp(n uint64) OpCode {
- return OpCode(c.GetByte(n))
- }
- // GetByte returns the n'th byte in the contract's byte array
- func (c *Contract) GetByte(n uint64) byte {
- if n < uint64(len(c.Code)) {
- return c.Code[n]
- }
- return 0
- }
- // Caller returns the caller of the contract.
- //
- // Caller will recursively call caller when the contract is a delegate
- // call, including that of caller's caller.
- func (c *Contract) Caller() common.Address {
- return c.CallerAddress
- }
- // UseGas attempts the use gas and subtracts it and returns true on success
- func (c *Contract) UseGas(gas uint64) (ok bool) {
- if c.Gas < gas {
- return false
- }
- c.Gas -= gas
- return true
- }
- // Address returns the contracts address
- func (c *Contract) Address() common.Address {
- return c.self.Address()
- }
- // Value returns the contract's value (sent to it from it's caller)
- func (c *Contract) Value() *big.Int {
- return c.value
- }
- // SetCallCode sets the code of the contract and address of the backing data
- // object
- func (c *Contract) SetCallCode(addr *common.Address, hash common.Hash, code []byte) {
- c.Code = code
- c.CodeHash = hash
- c.CodeAddr = addr
- }
- // SetCodeOptionalHash can be used to provide code, but it's optional to provide hash.
- // In case hash is not provided, the jumpdest analysis will not be saved to the parent context
- func (c *Contract) SetCodeOptionalHash(addr *common.Address, codeAndHash *codeAndHash) {
- c.Code = codeAndHash.code
- c.CodeHash = codeAndHash.hash
- c.CodeAddr = addr
- }
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