aboutsummaryrefslogtreecommitdiffstats
path: root/accounts/abi/bind/backends/simulated.go
blob: 0621e81c2b5c4a87b72e37a1c8cb94b431a8ee6f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
// 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 backends

import (
    "context"
    "errors"
    "fmt"
    "math/big"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/accounts/abi/bind"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/math"
    "github.com/ethereum/go-ethereum/consensus/ethash"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/core/vm"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/params"
)

// This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
var _ bind.ContractBackend = (*SimulatedBackend)(nil)

var errBlockNumberUnsupported = errors.New("SimulatedBackend cannot access blocks other than the latest block")

// SimulatedBackend implements bind.ContractBackend, simulating a blockchain in
// the background. Its main purpose is to allow easily testing contract bindings.
type SimulatedBackend struct {
    database   ethdb.Database   // In memory database to store our testing data
    blockchain *core.BlockChain // Ethereum blockchain to handle the consensus

    mu           sync.Mutex
    pendingBlock *types.Block   // Currently pending block that will be imported on request
    pendingState *state.StateDB // Currently pending state that will be the active on on request

    config *params.ChainConfig
}

// NewSimulatedBackend creates a new binding backend using a simulated blockchain
// for testing purposes.
func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
    database, _ := ethdb.NewMemDatabase()
    genesis := core.Genesis{Config: params.AllProtocolChanges, Alloc: alloc}
    genesis.MustCommit(database)
    blockchain, _ := core.NewBlockChain(database, genesis.Config, ethash.NewFaker(), vm.Config{})
    backend := &SimulatedBackend{database: database, blockchain: blockchain, config: genesis.Config}
    backend.rollback()
    return backend
}

// Commit imports all the pending transactions as a single block and starts a
// fresh new state.
func (b *SimulatedBackend) Commit() {
    b.mu.Lock()
    defer b.mu.Unlock()

    if _, err := b.blockchain.InsertChain([]*types.Block{b.pendingBlock}); err != nil {
        panic(err) // This cannot happen unless the simulator is wrong, fail in that case
    }
    b.rollback()
}

// Rollback aborts all pending transactions, reverting to the last committed state.
func (b *SimulatedBackend) Rollback() {
    b.mu.Lock()
    defer b.mu.Unlock()

    b.rollback()
}

func (b *SimulatedBackend) rollback() {
    blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
    b.pendingBlock = blocks[0]
    b.pendingState, _ = state.New(b.pendingBlock.Root(), state.NewDatabase(b.database))
}

// CodeAt returns the code associated with a certain account in the blockchain.
func (b *SimulatedBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
        return nil, errBlockNumberUnsupported
    }
    statedb, _ := b.blockchain.State()
    return statedb.GetCode(contract), nil
}

// BalanceAt returns the wei balance of a certain account in the blockchain.
func (b *SimulatedBackend) BalanceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (*big.Int, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
        return nil, errBlockNumberUnsupported
    }
    statedb, _ := b.blockchain.State()
    return statedb.GetBalance(contract), nil
}

// NonceAt returns the nonce of a certain account in the blockchain.
func (b *SimulatedBackend) NonceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (uint64, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
        return 0, errBlockNumberUnsupported
    }
    statedb, _ := b.blockchain.State()
    return statedb.GetNonce(contract), nil
}

// StorageAt returns the value of key in the storage of an account in the blockchain.
func (b *SimulatedBackend) StorageAt(ctx context.Context, contract common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
        return nil, errBlockNumberUnsupported
    }
    statedb, _ := b.blockchain.State()
    val := statedb.GetState(contract, key)
    return val[:], nil
}

// TransactionReceipt returns the receipt of a transaction.
func (b *SimulatedBackend) TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error) {
    receipt, _, _, _ := core.GetReceipt(b.database, txHash)
    return receipt, nil
}

// PendingCodeAt returns the code associated with an account in the pending state.
func (b *SimulatedBackend) PendingCodeAt(ctx context.Context, contract common.Address) ([]byte, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    return b.pendingState.GetCode(contract), nil
}

// CallContract executes a contract call.
func (b *SimulatedBackend) CallContract(ctx context.Context, call ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
        return nil, errBlockNumberUnsupported
    }
    state, err := b.blockchain.State()
    if err != nil {
        return nil, err
    }
    rval, _, _, err := b.callContract(ctx, call, b.blockchain.CurrentBlock(), state)
    return rval, err
}

// PendingCallContract executes a contract call on the pending state.
func (b *SimulatedBackend) PendingCallContract(ctx context.Context, call ethereum.CallMsg) ([]byte, error) {
    b.mu.Lock()
    defer b.mu.Unlock()
    defer b.pendingState.RevertToSnapshot(b.pendingState.Snapshot())

    rval, _, _, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState)
    return rval, err
}

// PendingNonceAt implements PendingStateReader.PendingNonceAt, retrieving
// the nonce currently pending for the account.
func (b *SimulatedBackend) PendingNonceAt(ctx context.Context, account common.Address) (uint64, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
}

// SuggestGasPrice implements ContractTransactor.SuggestGasPrice. Since the simulated
// chain doens't have miners, we just return a gas price of 1 for any call.
func (b *SimulatedBackend) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
    return big.NewInt(1), nil
}

// EstimateGas executes the requested code against the currently pending block/state and
// returns the used amount of gas.
func (b *SimulatedBackend) EstimateGas(ctx context.Context, call ethereum.CallMsg) (*big.Int, error) {
    b.mu.Lock()
    defer b.mu.Unlock()

    // Binary search the gas requirement, as it may be higher than the amount used
    var (
        lo uint64 = params.TxGas - 1
        hi uint64
    )
    if call.Gas != nil && call.Gas.Uint64() >= params.TxGas {
        hi = call.Gas.Uint64()
    } else {
        hi = b.pendingBlock.GasLimit().Uint64()
    }
    for lo+1 < hi {
        // Take a guess at the gas, and check transaction validity
        mid := (hi + lo) / 2
        call.Gas = new(big.Int).SetUint64(mid)

        snapshot := b.pendingState.Snapshot()
        _, _, failed, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState)
        b.pendingState.RevertToSnapshot(snapshot)

        // If the transaction became invalid or execution failed, raise the gas limit
        if err != nil || failed {
            lo = mid
            continue
        }
        // Otherwise assume the transaction succeeded, lower the gas limit
        hi = mid
    }
    return new(big.Int).SetUint64(hi), nil
}

// callContract implemens common code between normal and pending contract calls.
// state is modified during execution, make sure to copy it if necessary.
func (b *SimulatedBackend) callContract(ctx context.Context, call ethereum.CallMsg, block *types.Block, statedb *state.StateDB) ([]byte, *big.Int, bool, error) {
    // Ensure message is initialized properly.
    if call.GasPrice == nil {
        call.GasPrice = big.NewInt(1)
    }
    if call.Gas == nil || call.Gas.Sign() == 0 {
        call.Gas = big.NewInt(50000000)
    }
    if call.Value == nil {
        call.Value = new(big.Int)
    }
    // Set infinite balance to the fake caller account.
    from := statedb.GetOrNewStateObject(call.From)
    from.SetBalance(math.MaxBig256)
    // Execute the call.
    msg := callmsg{call}

    evmContext := core.NewEVMContext(msg, block.Header(), b.blockchain, nil)
    // Create a new environment which holds all relevant information
    // about the transaction and calling mechanisms.
    vmenv := vm.NewEVM(evmContext, statedb, b.config, vm.Config{})
    gaspool := new(core.GasPool).AddGas(math.MaxBig256)
    ret, gasUsed, _, failed, err := core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
    return ret, gasUsed, failed, err
}

// SendTransaction updates the pending block to include the given transaction.
// It panics if the transaction is invalid.
func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transaction) error {
    b.mu.Lock()
    defer b.mu.Unlock()

    sender, err := types.Sender(types.HomesteadSigner{}, tx)
    if err != nil {
        panic(fmt.Errorf("invalid transaction: %v", err))
    }
    nonce := b.pendingState.GetNonce(sender)
    if tx.Nonce() != nonce {
        panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
    }

    blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
        for _, tx := range b.pendingBlock.Transactions() {
            block.AddTx(tx)
        }
        block.AddTx(tx)
    })
    b.pendingBlock = blocks[0]
    b.pendingState, _ = state.New(b.pendingBlock.Root(), state.NewDatabase(b.database))
    return nil
}

// JumpTimeInSeconds adds skip seconds to the clock
func (b *SimulatedBackend) AdjustTime(adjustment time.Duration) error {
    b.mu.Lock()
    defer b.mu.Unlock()
    blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
        for _, tx := range b.pendingBlock.Transactions() {
            block.AddTx(tx)
        }
        block.OffsetTime(int64(adjustment.Seconds()))
    })
    b.pendingBlock = blocks[0]
    b.pendingState, _ = state.New(b.pendingBlock.Root(), state.NewDatabase(b.database))

    return nil
}

// callmsg implements core.Message to allow passing it as a transaction simulator.
type callmsg struct {
    ethereum.CallMsg
}

func (m callmsg) From() common.Address { return m.CallMsg.From }
func (m callmsg) Nonce() uint64        { return 0 }
func (m callmsg) CheckNonce() bool     { return false }
func (m callmsg) To() *common.Address  { return m.CallMsg.To }
func (m callmsg) GasPrice() *big.Int   { return m.CallMsg.GasPrice }
func (m callmsg) Gas() *big.Int        { return m.CallMsg.Gas }
func (m callmsg) Value() *big.Int      { return m.CallMsg.Value }
func (m callmsg) Data() []byte         { return m.CallMsg.Data }