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94 lines
2.9 KiB
94 lines
2.9 KiB
6 years ago
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package swap
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import (
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"errors"
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"fmt"
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"strconv"
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"sync"
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"github.com/ethereum/go-ethereum/p2p/enode"
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"github.com/ethereum/go-ethereum/p2p/protocols"
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"github.com/ethereum/go-ethereum/swarm/log"
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"github.com/ethereum/go-ethereum/swarm/state"
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)
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// SwAP Swarm Accounting Protocol
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// a peer to peer micropayment system
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// A node maintains an individual balance with every peer
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// Only messages which have a price will be accounted for
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type Swap struct {
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stateStore state.Store //stateStore is needed in order to keep balances across sessions
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lock sync.RWMutex //lock the balances
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balances map[enode.ID]int64 //map of balances for each peer
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}
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// New - swap constructor
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func New(stateStore state.Store) (swap *Swap) {
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swap = &Swap{
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stateStore: stateStore,
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balances: make(map[enode.ID]int64),
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}
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return
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}
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//Swap implements the protocols.Balance interface
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//Add is the (sole) accounting function
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func (s *Swap) Add(amount int64, peer *protocols.Peer) (err error) {
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s.lock.Lock()
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defer s.lock.Unlock()
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//load existing balances from the state store
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err = s.loadState(peer)
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if err != nil && err != state.ErrNotFound {
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return
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}
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//adjust the balance
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//if amount is negative, it will decrease, otherwise increase
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s.balances[peer.ID()] += amount
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//save the new balance to the state store
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peerBalance := s.balances[peer.ID()]
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err = s.stateStore.Put(peer.ID().String(), &peerBalance)
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log.Debug(fmt.Sprintf("balance for peer %s: %s", peer.ID().String(), strconv.FormatInt(peerBalance, 10)))
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return err
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}
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//GetPeerBalance returns the balance for a given peer
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func (swap *Swap) GetPeerBalance(peer enode.ID) (int64, error) {
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swap.lock.RLock()
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defer swap.lock.RUnlock()
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if p, ok := swap.balances[peer]; ok {
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return p, nil
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}
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return 0, errors.New("Peer not found")
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}
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//load balances from the state store (persisted)
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func (s *Swap) loadState(peer *protocols.Peer) (err error) {
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var peerBalance int64
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peerID := peer.ID()
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//only load if the current instance doesn't already have this peer's
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//balance in memory
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if _, ok := s.balances[peerID]; !ok {
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err = s.stateStore.Get(peerID.String(), &peerBalance)
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s.balances[peerID] = peerBalance
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}
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return
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}
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