aboutsummaryrefslogtreecommitdiffstats
path: root/accounts/abi/bind/backends/simulated.go
blob: 17a0ed7fe709b90d82514cb0f68184084b9acd29 (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
// Copyright 2016 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 (
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "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/ethdb"
    "github.com/ethereum/go-ethereum/event"
)

// 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

    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
}

// NewSimulatedBackend creates a new binding backend using a simulated blockchain
// for testing purposes.
func NewSimulatedBackend(accounts ...core.GenesisAccount) *SimulatedBackend {
    database, _ := ethdb.NewMemDatabase()
    core.WriteGenesisBlockForTesting(database, accounts...)
    blockchain, _ := core.NewBlockChain(database, new(core.FakePow), new(event.TypeMux))

    backend := &SimulatedBackend{
        database:   database,
        blockchain: blockchain,
    }
    backend.Rollback()

    return backend
}

// Commit imports all the pending transactions as a single block and starts a
// fresh new state.
func (b *SimulatedBackend) Commit() {
    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() {
    blocks, _ := core.GenerateChain(b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})

    b.pendingBlock = blocks[0]
    b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
}

// ContractCall implements ContractCaller.ContractCall, executing the specified
// contract with the given input data.
func (b *SimulatedBackend) ContractCall(contract common.Address, data []byte, pending bool) ([]byte, error) {
    // Create a copy of the current state db to screw around with
    var (
        block   *types.Block
        statedb *state.StateDB
    )
    if pending {
        block, statedb = b.pendingBlock, b.pendingState
    } else {
        block = b.blockchain.CurrentBlock()
        statedb, _ = b.blockchain.State()
    }
    statedb = statedb.Copy()

    // Set infinite balance to the a fake caller account
    from := statedb.GetOrNewStateObject(common.Address{})
    from.SetBalance(common.MaxBig)

    // Assemble the call invocation to measure the gas usage
    msg := callmsg{
        from:     from,
        to:       &contract,
        gasPrice: new(big.Int),
        gasLimit: common.MaxBig,
        value:    new(big.Int),
        data:     data,
    }
    // Execute the call and return
    vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header())
    gaspool := new(core.GasPool).AddGas(common.MaxBig)

    out, _, err := core.ApplyMessage(vmenv, msg, gaspool)
    return out, err
}

// AccountNonce implements ContractTransactor.AccountNonce, retrieving the nonce
// currently pending for the account.
func (b *SimulatedBackend) AccountNonce(account common.Address) (uint64, error) {
    return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
}

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

// GasLimit implements ContractTransactor.GasLimit, executing the requested code
// against the currently pending block/state and returning the used gas.
func (b *SimulatedBackend) GasLimit(sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
    // Create a copy of the currently pending state db to screw around with
    var (
        block   = b.pendingBlock
        statedb = b.pendingState.Copy()
    )

    // Set infinite balance to the a fake caller account
    from := statedb.GetOrNewStateObject(sender)
    from.SetBalance(common.MaxBig)

    // Assemble the call invocation to measure the gas usage
    msg := callmsg{
        from:     from,
        to:       contract,
        gasPrice: new(big.Int),
        gasLimit: common.MaxBig,
        value:    value,
        data:     data,
    }
    // Execute the call and return
    vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header())
    gaspool := new(core.GasPool).AddGas(common.MaxBig)

    _, gas, err := core.ApplyMessage(vmenv, msg, gaspool)
    return gas, err
}

// Transact implements ContractTransactor.SendTransaction, delegating the raw
// transaction injection to the remote node.
func (b *SimulatedBackend) SendTransaction(tx *types.Transaction) error {
    blocks, _ := core.GenerateChain(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(), b.database)

    return nil
}

// callmsg implements core.Message to allow passing it as a transaction simulator.
type callmsg struct {
    from     *state.StateObject
    to       *common.Address
    gasLimit *big.Int
    gasPrice *big.Int
    value    *big.Int
    data     []byte
}

func (m callmsg) From() (common.Address, error)         { return m.from.Address(), nil }
func (m callmsg) FromFrontier() (common.Address, error) { return m.from.Address(), nil }
func (m callmsg) Nonce() uint64                         { return m.from.Nonce() }
func (m callmsg) To() *common.Address                   { return m.to }
func (m callmsg) GasPrice() *big.Int                    { return m.gasPrice }
func (m callmsg) Gas() *big.Int                         { return m.gasLimit }
func (m callmsg) Value() *big.Int                       { return m.value }
func (m callmsg) Data() []byte                          { return m.data }