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 (
    "errors"
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/state"
)

// Environment is is required by the virtual machine to get information from
// it's own isolated environment. For an example see `core.VMEnv`
type Environment interface {
    State() *state.StateDB

    Origin() common.Address
    BlockNumber() *big.Int
    GetHash(n uint64) common.Hash
    Coinbase() common.Address
    Time() *big.Int
    Difficulty() *big.Int
    GasLimit() *big.Int
    CanTransfer(from Account, balance *big.Int) bool
    Transfer(from, to Account, amount *big.Int) error
    AddLog(*state.Log)
    AddStructLog(StructLog)
    StructLogs() []StructLog

    VmType() Type

    Depth() int
    SetDepth(i int)

    Call(me ContextRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
    CallCode(me ContextRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
    Create(me ContextRef, data []byte, gas, price, value *big.Int) ([]byte, error, ContextRef)
}

// StructLog is emited to the Environment each cycle and lists information about the curent 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)
    Balance() *big.Int
    Address() common.Address
}

// generic transfer method
func Transfer(from, to Account, amount *big.Int) error {
    if from.Balance().Cmp(amount) < 0 {
        return errors.New("Insufficient balance in account")
    }

    from.SubBalance(amount)
    to.AddBalance(amount)

    return nil
}