Merge pull request #2956 from fjl/chequebook

contracts/chequebook: add chequebook contract wrapper

contracts/chequebook/api.go

+// 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 chequebook
+
+import (
+	"errors"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+const Version = "1.0"
+
+var errNoChequebook = errors.New("no chequebook")
+
+type Api struct {
+	chequebookf func() *Chequebook
+}
+
+func NewApi(ch func() *Chequebook) *Api {
+	return &Api{ch}
+}
+
+func (self *Api) Balance() (string, error) {
+	ch := self.chequebookf()
+	if ch == nil {
+		return "", errNoChequebook
+	}
+	return ch.Balance().String(), nil
+}
+
+func (self *Api) Issue(beneficiary common.Address, amount *big.Int) (cheque *Cheque, err error) {
+	ch := self.chequebookf()
+	if ch == nil {
+		return nil, errNoChequebook
+	}
+	return ch.Issue(beneficiary, amount)
+}
+
+func (self *Api) Cash(cheque *Cheque) (txhash string, err error) {
+	ch := self.chequebookf()
+	if ch == nil {
+		return "", errNoChequebook
+	}
+	return ch.Cash(cheque)
+}
+
+func (self *Api) Deposit(amount *big.Int) (txhash string, err error) {
+	ch := self.chequebookf()
+	if ch == nil {
+		return "", errNoChequebook
+	}
+	return ch.Deposit(amount)
+}

contracts/chequebook/contract/chequebook.sol

+import "mortal";
+
+/// @title Chequebook for Ethereum micropayments
+/// @author Daniel A. Nagy <daniel@ethdev.com>
+contract chequebook is mortal {
+    // Cumulative paid amount in wei to each beneficiary
+    mapping (address => uint256) public sent;
+
+    /// @notice Overdraft event
+    event Overdraft(address deadbeat);
+
+    /// @notice Cash cheque
+    ///
+    /// @param beneficiary beneficiary address
+    /// @param amount cumulative amount in wei
+    /// @param sig_v signature parameter v
+    /// @param sig_r signature parameter r
+    /// @param sig_s signature parameter s
+    /// The digital signature is calculated on the concatenated triplet of contract address, beneficiary address and cumulative amount
+    function cash(address beneficiary, uint256 amount,
+        uint8 sig_v, bytes32 sig_r, bytes32 sig_s) {
+        // Check if the cheque is old.
+        // Only cheques that are more recent than the last cashed one are considered.
+        if(amount <= sent[beneficiary]) return;
+        // Check the digital signature of the cheque.
+        bytes32 hash = sha3(address(this), beneficiary, amount);
+        if(owner != ecrecover(hash, sig_v, sig_r, sig_s)) return;
+        // Attempt sending the difference between the cumulative amount on the cheque
+        // and the cumulative amount on the last cashed cheque to beneficiary.
+        if (amount - sent[beneficiary] >= this.balance) {
+            if (beneficiary.send(amount - sent[beneficiary])) {
+                // Upon success, update the cumulative amount.
+                sent[beneficiary] = amount;
+            }
+        } else {
+            // Upon failure, punish owner for writing a bounced cheque.
+            // owner.sendToDebtorsPrison();
+            Overdraft(owner);
+            // Compensate beneficiary.
+            suicide(beneficiary);
+        }
+    }
+}

contracts/chequebook/contract/code.go

+// 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 contract
+
+// ContractDeployedCode is used to detect suicides. This constant needs to be
+// updated when the contract code is changed.
+const ContractDeployedCode = "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"

contracts/chequebook/gencode.go

+// 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/>.
+
+// +build none
+
+// This program generates contract/code.go, which contains the chequebook code
+// after deployment.
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind/backends"
+	"github.com/ethereum/go-ethereum/contracts/chequebook/contract"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+var (
+	testKey, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	testAccount = core.GenesisAccount{
+		Address: crypto.PubkeyToAddress(testKey.PublicKey),
+		Balance: big.NewInt(500000000000),
+	}
+)
+
+func main() {
+	backend := backends.NewSimulatedBackend(testAccount)
+	auth := bind.NewKeyedTransactor(testKey)
+
+	// Deploy the contract, get the code.
+	addr, _, _, err := contract.DeployChequebook(auth, backend)
+	if err != nil {
+		panic(err)
+	}
+	backend.Commit()
+	code, err := backend.CodeAt(nil, addr, nil)
+	if err != nil {
+		panic(err)
+	}
+	if len(code) == 0 {
+		panic("empty code")
+	}
+
+	// Write the output file.
+	content := fmt.Sprintf(`// TODO: insert license header
+
+package contract
+
+// ContractDeployedCode is used to detect suicides. This constant needs to be
+// updated when the contract code is changed.
+const ContractDeployedCode = "%#x"
+`, code)
+	if err := ioutil.WriteFile("contract/code.go", []byte(content), 0644); err != nil {
+		panic(err)
+	}
+}