path: root/light/state_object.go

// 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 light

import (
    "bytes"
    "fmt"
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/rlp"
    "golang.org/x/net/context"
)

var emptyCodeHash = crypto.Keccak256(nil)

// Code represents a contract code in binary form
type Code []byte

// String returns a string representation of the code
func (self Code) String() string {
    return string(self) //strings.Join(Disassemble(self), " ")
}

// Storage is a memory map cache of a contract storage
type Storage map[common.Hash]common.Hash

// String returns a string representation of the storage cache
func (self Storage) String() (str string) {
    for key, value := range self {
        str += fmt.Sprintf("%X : %X\n", key, value)
    }

    return
}

// Copy copies the contents of a storage cache
func (self Storage) Copy() Storage {
    cpy := make(Storage)
    for key, value := range self {
        cpy[key] = value
    }

    return cpy
}

// StateObject is a memory representation of an account or contract and its storage.
// This version is ODR capable, caching only the already accessed part of the
// storage, retrieving unknown parts on-demand from the ODR backend. Changes are
// never stored in the local database, only in the memory objects.
type StateObject struct {
    odr  OdrBackend
    trie *LightTrie

    // Address belonging to this account
    address common.Address
    // The balance of the account
    balance *big.Int
    // The nonce of the account
    nonce uint64
    // The code hash if code is present (i.e. a contract)
    codeHash []byte
    // The code for this account
    code Code
    // Cached storage (flushed when updated)
    storage Storage

    // Mark for deletion
    // When an object is marked for deletion it will be delete from the trie
    // during the "update" phase of the state transition
    remove  bool
    deleted bool
    dirty   bool
}

// NewStateObject creates a new StateObject of the specified account address
func NewStateObject(address common.Address, odr OdrBackend) *StateObject {
    object := &StateObject{
        odr:      odr,
        address:  address,
        balance:  new(big.Int),
        dirty:    true,
        codeHash: emptyCodeHash,
        storage:  make(Storage),
    }
    object.trie = NewLightTrie(&TrieID{}, odr, true)
    return object
}

// MarkForDeletion marks an account to be removed
func (self *StateObject) MarkForDeletion() {
    self.remove = true
    self.dirty = true
}

// getAddr gets the storage value at the given address from the trie
func (c *StateObject) getAddr(ctx context.Context, addr common.Hash) (common.Hash, error) {
    var ret []byte
    val, err := c.trie.Get(ctx, addr[:])
    if err != nil {
        return common.Hash{}, err
    }
    rlp.DecodeBytes(val, &ret)
    return common.BytesToHash(ret), nil
}

// Storage returns the storage cache object of the account
func (self *StateObject) Storage() Storage {
    return self.storage
}

// GetState returns the storage value at the given address from either the cache
// or the trie
func (self *StateObject) GetState(ctx context.Context, key common.Hash) (common.Hash, error) {
    value, exists := self.storage[key]
    if !exists {
        var err error
        value, err = self.getAddr(ctx, key)
        if err != nil {
            return common.Hash{}, err
        }
        if (value != common.Hash{}) {
            self.storage[key] = value
        }
    }

    return value, nil
}

// SetState sets the storage value at the given address
func (self *StateObject) SetState(k, value common.Hash) {
    self.storage[k] = value
    self.dirty = true
}

// AddBalance adds the given amount to the account balance
func (c *StateObject) AddBalance(amount *big.Int) {
    c.SetBalance(new(big.Int).Add(c.balance, amount))
}

// SubBalance subtracts the given amount from the account balance
func (c *StateObject) SubBalance(amount *big.Int) {
    c.SetBalance(new(big.Int).Sub(c.balance, amount))
}

// SetBalance sets the account balance to the given amount
func (c *StateObject) SetBalance(amount *big.Int) {
    c.balance = amount
    c.dirty = true
}

// ReturnGas returns the gas back to the origin. Used by the Virtual machine or Closures
func (c *StateObject) ReturnGas(gas *big.Int) {}

// Copy creates a copy of the state object
func (self *StateObject) Copy() *StateObject {
    stateObject := NewStateObject(self.Address(), self.odr)
    stateObject.balance.Set(self.balance)
    stateObject.codeHash = common.CopyBytes(self.codeHash)
    stateObject.nonce = self.nonce
    stateObject.trie = self.trie
    stateObject.code = self.code
    stateObject.storage = self.storage.Copy()
    stateObject.remove = self.remove
    stateObject.dirty = self.dirty
    stateObject.deleted = self.deleted

    return stateObject
}

//
// Attribute accessors
//

// empty returns whether the account is considered empty.
func (self *StateObject) empty() bool {
    return self.nonce == 0 && self.balance.Sign() == 0 && bytes.Equal(self.codeHash, emptyCodeHash)
}

// Balance returns the account balance
func (self *StateObject) Balance() *big.Int {
    return self.balance
}

// Address returns the address of the contract/account
func (self *StateObject) Address() common.Address {
    return self.address
}

// Code returns the contract code
func (self *StateObject) Code() []byte {
    return self.code
}

// SetCode sets the contract code
func (self *StateObject) SetCode(hash common.Hash, code []byte) {
    self.code = code
    self.codeHash = hash[:]
    self.dirty = true
}

// SetNonce sets the account nonce
func (self *StateObject) SetNonce(nonce uint64) {
    self.nonce = nonce
    self.dirty = true
}

// Nonce returns the account nonce
func (self *StateObject) Nonce() uint64 {
    return self.nonce
}

// ForEachStorage calls a callback function for every key/value pair found
// in the local storage cache. Note that unlike core/state.StateObject,
// light.StateObject only returns cached values and doesn't download the
// entire storage tree.
func (self *StateObject) ForEachStorage(cb func(key, value common.Hash) bool) {
    for h, v := range self.storage {
        cb(h, v)
    }
}

// Never called, but must be present to allow StateObject to be used
// as a vm.Account interface that also satisfies the vm.ContractRef
// interface. Interfaces are awesome.
func (self *StateObject) Value() *big.Int {
    panic("Value on StateObject should never be called")
}

// Encoding

type extStateObject struct {
    Nonce    uint64
    Balance  *big.Int
    Root     common.Hash
    CodeHash []byte
}

// DecodeObject decodes an RLP-encoded state object.
func DecodeObject(ctx context.Context, stateID *TrieID, address common.Address, odr OdrBackend, data []byte) (*StateObject, error) {
    var (
        obj = &StateObject{address: address, odr: odr, storage: make(Storage)}
        ext extStateObject
        err error
    )
    if err = rlp.DecodeBytes(data, &ext); err != nil {
        return nil, err
    }
    trieID := StorageTrieID(stateID, address, ext.Root)
    obj.trie = NewLightTrie(trieID, odr, true)
    if !bytes.Equal(ext.CodeHash, emptyCodeHash) {
        if obj.code, err = retrieveContractCode(ctx, obj.odr, trieID, common.BytesToHash(ext.CodeHash)); err != nil {
            return nil, fmt.Errorf("can't find code for hash %x: %v", ext.CodeHash, err)
        }
    }
    obj.nonce = ext.Nonce
    obj.balance = ext.Balance
    obj.codeHash = ext.CodeHash
    return obj, nil
}