path: root/core/vm/environment.go

// Copyright 2014 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"
)

// Environment is is required by the virtual machine to get information from
// it's own isolated environment.

// Environment is an EVM requirement and helper which allows access to outside
// information such as states.
type Environment interface {
    // The state database
    Db() Database
    // Creates a restorable snapshot
    MakeSnapshot() Database
    // Set database to previous snapshot
    SetSnapshot(Database)
    // Address of the original invoker (first occurrence of the VM invoker)
    Origin() common.Address
    // The block number this VM is invoked on
    BlockNumber() *big.Int
    // The n'th hash ago from this block number
    GetHash(uint64) common.Hash
    // The handler's address
    Coinbase() common.Address
    // The current time (block time)
    Time() *big.Int
    // Difficulty set on the current block
    Difficulty() *big.Int
    // The gas limit of the block
    GasLimit() *big.Int
    // Determines whether it's possible to transact
    CanTransfer(from common.Address, balance *big.Int) bool
    // Transfers amount from one account to the other
    Transfer(from, to Account, amount *big.Int)
    // Adds a LOG to the state
    AddLog(*Log)
    // Adds a structured log to the env
    AddStructLog(StructLog)
    // Returns all coalesced structured logs
    StructLogs() []StructLog
    // Type of the VM
    Vm() *Vm
    // Current calling depth
    Depth() int
    SetDepth(i int)

    // Call another contract
    Call(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
    // Take another's contract code and execute within our own context
    CallCode(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
    // Same as CallCode except sender and value is propagated from parent to child scope
    DelegateCall(me ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error)
    // Create a new contract
    Create(me ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error)
}

// Database is a EVM database for full state querying
type Database interface {
    GetAccount(common.Address) Account
    CreateAccount(common.Address) Account

    AddBalance(common.Address, *big.Int)
    GetBalance(common.Address) *big.Int

    GetNonce(common.Address) uint64
    SetNonce(common.Address, uint64)

    GetCode(common.Address) []byte
    SetCode(common.Address, []byte)

    AddRefund(*big.Int)
    GetRefund() *big.Int

    GetState(common.Address, common.Hash) common.Hash
    SetState(common.Address, common.Hash, common.Hash)

    Delete(common.Address) bool
    Exist(common.Address) bool
    IsDeleted(common.Address) bool
}

// StructLog is emitted to the Environment each cycle and lists information about the current internal state
// prior to the execution of the statement.
type StructLog struct {
    Pc      uint64
    Op      OpCode
    Gas     *big.Int
    GasCost *big.Int
    Memory  []byte
    Stack   []*big.Int
    Storage map[common.Hash][]byte
    Err     error
}

type Account interface {
    SubBalance(amount *big.Int)
    AddBalance(amount *big.Int)
    SetBalance(*big.Int)
    SetNonce(uint64)
    Balance() *big.Int
    Address() common.Address
    ReturnGas(*big.Int, *big.Int)
    SetCode([]byte)
    EachStorage(cb func(key, value []byte))
    Value() *big.Int
}