2017-05-21 18:35:27 -07:00
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package chainview
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import (
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"fmt"
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"sync"
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"sync/atomic"
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"github.com/roasbeef/btcd/chaincfg/chainhash"
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"github.com/roasbeef/btcd/wire"
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"github.com/roasbeef/btcrpcclient"
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"github.com/roasbeef/btcutil"
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"github.com/roasbeef/btcwallet/waddrmgr"
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"github.com/lightninglabs/neutrino"
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)
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// CfFilteredChainView is an implementation of the FilteredChainView interface
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// which is supported by an underlying Bitcoin light client which supports
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// client side filtering of Golomb Coded Sets. Rather than fetching all the
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// blocks, the light client is able to query fitlers locally, to test if an
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// item in ablock modifies any of our watched set of UTXOs/
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type CfFilteredChainView struct {
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started int32
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stopped int32
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// p2pNode is a pointer to the running GCS-filter supported Bitcoin
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// light clientl
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p2pNode *neutrino.ChainService
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// chainView is the active rescan which only watches our specified
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// sub-set of the UTXO set.
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chainView neutrino.Rescan
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// rescanErrChan is the channel that any errors encountered during the
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// rescan will be sent over.
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rescanErrChan <-chan error
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// newBlocks is the channel in which new filtered blocks are sent over.
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newBlocks chan *FilteredBlock
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// staleBlocks is the channel in which blocks that have been
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// disconnected from the mainchain are sent over.
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staleBlocks chan *FilteredBlock
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// filterUpdates is a channel in which updates to the utxo filter
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// attached to this instance are sent over.
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filterUpdates chan filterUpdate
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// chainFilter is the
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filterMtx sync.RWMutex
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chainFilter map[wire.OutPoint]struct{}
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quit chan struct{}
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wg sync.WaitGroup
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}
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// A compile time check to ensure CfFilteredChainView implements the
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// chainview.FilteredChainView.
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var _ FilteredChainView = (*CfFilteredChainView)(nil)
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// NewCfFilteredChainView creates a new instance of the CfFilteredChainView
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// which is connected to an active neutrino node.
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//
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// NOTE: The node should already be running an syncing before being passed into
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// this function.
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func NewCfFilteredChainView(node *neutrino.ChainService) (*CfFilteredChainView, error) {
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return &CfFilteredChainView{
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newBlocks: make(chan *FilteredBlock),
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staleBlocks: make(chan *FilteredBlock),
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quit: make(chan struct{}),
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rescanErrChan: make(chan error),
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filterUpdates: make(chan filterUpdate),
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chainFilter: make(map[wire.OutPoint]struct{}),
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p2pNode: node,
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}, nil
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}
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// Start kicks off the FilteredChainView implementation. This function must be
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// called before any calls to UpdateFilter can be processed.
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2017-05-23 18:13:45 -07:00
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//
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2017-05-21 18:35:27 -07:00
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) Start() error {
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// Already started?
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if atomic.AddInt32(&c.started, 1) != 1 {
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return nil
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}
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log.Infof("FilteredChainView starting")
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// First, we'll obtain the latest block height of the p2p node. We'll
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// start the auto-rescan from this point. Once a caller actually wishes
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// to register a chain view, the rescan state will be rewound
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// accordingly.
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bestHeader, bestHeight, err := c.p2pNode.LatestBlock()
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if err != nil {
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return err
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}
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startingPoint := &waddrmgr.BlockStamp{
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Height: int32(bestHeight),
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Hash: bestHeader.BlockHash(),
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}
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// Next, we'll create our set of rescan options. Currently it's
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// required that a user MUST set a addr/outpoint/txid when creating a
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// rescan. To get around this, we'll add a "zero" outpoint, that won't
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// actually be matched.
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var zeroPoint wire.OutPoint
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rescanOptions := []neutrino.RescanOption{
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neutrino.StartBlock(startingPoint),
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neutrino.QuitChan(c.quit),
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neutrino.NotificationHandlers(
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btcrpcclient.NotificationHandlers{
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OnFilteredBlockConnected: c.onFilteredBlockConnected,
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OnFilteredBlockDisconnected: c.onFilteredBlockDisconnected,
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},
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),
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neutrino.WatchOutPoints(zeroPoint),
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}
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// Finally, we'll create our rescan struct, start it, and launch all
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// the goroutines we need to operate this FilteredChainView instance.
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c.chainView = c.p2pNode.NewRescan(rescanOptions...)
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c.rescanErrChan = c.chainView.Start()
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c.wg.Add(1)
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go c.chainFilterer()
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return nil
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}
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// Stop signals all active goroutines for a graceful shutdown.
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//
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) Stop() error {
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// Already shutting down?
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if atomic.AddInt32(&c.stopped, 1) != 1 {
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return nil
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}
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log.Infof("FilteredChainView stopping")
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close(c.quit)
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c.wg.Wait()
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return nil
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}
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// onFilteredBlockConnected is called for each block that's connected to the
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// end of the main chain. Based on our current chain filter, the block may or
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// may not include any relevant transactions.
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func (c *CfFilteredChainView) onFilteredBlockConnected(height int32,
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header *wire.BlockHeader, txns []*btcutil.Tx) {
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mtxs := make([]*wire.MsgTx, len(txns))
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for i, tx := range txns {
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mtx := tx.MsgTx()
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mtxs[i] = mtx
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for _, txIn := range mtx.TxIn {
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c.filterMtx.Lock()
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delete(c.chainFilter, txIn.PreviousOutPoint)
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c.filterMtx.Unlock()
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}
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}
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go func() {
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c.newBlocks <- &FilteredBlock{
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Hash: header.BlockHash(),
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Height: uint32(height),
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Transactions: mtxs,
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}
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}()
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}
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// onFilteredBlockDisconnected is a callback which is executed once a block is
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// disconnected from the end of the main chain.
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func (c *CfFilteredChainView) onFilteredBlockDisconnected(height int32,
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header *wire.BlockHeader) {
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go func() {
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c.staleBlocks <- &FilteredBlock{
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Hash: header.BlockHash(),
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Height: uint32(height),
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}
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}()
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}
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// chainFilterer is the primary coordination goroutine within the
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// CfFilteredChainView. This goroutine handles errors from the running rescan,
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// and also filter updates.
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func (c *CfFilteredChainView) chainFilterer() {
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defer c.wg.Done()
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for {
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select {
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case err := <-c.rescanErrChan:
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log.Errorf("Error encountered during rescan: %v", err)
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// We've received a new update to the filter from the caller to
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// mutate their established chain view.
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case update := <-c.filterUpdates:
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log.Debugf("Updating chain filter with new UTXO's: %v",
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update.newUtxos)
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// First, we'll update the current chain view, by
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// adding any new UTXO's, ignoring duplicates int he
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// process.
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c.filterMtx.Lock()
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for _, op := range update.newUtxos {
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c.chainFilter[op] = struct{}{}
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}
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c.filterMtx.Unlock()
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// With our internal chain view update, we'll craft a
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// new update to the chainView which includes our new
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2017-05-23 18:13:45 -07:00
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// UTXO's, and current update height.
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2017-05-21 18:35:27 -07:00
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rescanUpdate := []neutrino.UpdateOption{
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neutrino.AddOutPoints(update.newUtxos...),
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neutrino.Rewind(update.updateHeight),
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}
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err := c.chainView.Update(rescanUpdate...)
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if err != nil {
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log.Errorf("unable to update rescan: %v", err)
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}
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case <-c.quit:
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return
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}
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}
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}
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// FilterBlock takes a block hash, and returns a FilteredBlocks which is the
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// result of applying the current registered UTXO sub-set on the block
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// corresponding to that block hash. If any watched UTXO's are spent by the
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// selected lock, then the internal chainFilter will also be updated.
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//
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) FilterBlock(blockHash *chainhash.Hash) (*FilteredBlock, error) {
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// As we need to manually filter a block, we'll first fetch the block
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// form the network.
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block, err := c.p2pNode.GetBlockFromNetwork(*blockHash)
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if err != nil {
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return nil, err
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}
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// Along with the block, we'll also need the height of the block in
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// order to complete the notification.
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_, blockHeight, err := c.p2pNode.GetBlockByHash(*blockHash)
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if err != nil {
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return nil, err
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}
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// Finally, we'll step through the block, input by input, to see if any
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// transactions spend any outputs from our watched sub-set of the UTXO
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// set.
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var filteredTxns []*wire.MsgTx
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for _, tx := range block.Transactions() {
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for _, txIn := range tx.MsgTx().TxIn {
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prevOp := txIn.PreviousOutPoint
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if _, ok := c.chainFilter[prevOp]; ok {
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filteredTxns = append(filteredTxns, tx.MsgTx())
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c.filterMtx.Lock()
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delete(c.chainFilter, prevOp)
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c.filterMtx.Unlock()
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break
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}
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}
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}
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return &FilteredBlock{
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Hash: *blockHash,
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Height: blockHeight,
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Transactions: filteredTxns,
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}, nil
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}
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// UpdateFilter updates the UTXO filter which is to be consulted when creating
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// FilteredBlocks to be sent to subscribed clients. This method is cumulative
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// meaning repeated calls to this method should _expand_ the size of the UTXO
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// sub-set currently being watched. If the set updateHeight is _lower_ than
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// the best known height of the implementation, then the state should be
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// rewound to ensure all relevant notifications are dispatched.
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//
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) UpdateFilter(ops []wire.OutPoint, updateHeight uint32) error {
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select {
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case c.filterUpdates <- filterUpdate{
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newUtxos: ops,
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updateHeight: updateHeight,
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}:
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return nil
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case <-c.quit:
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return fmt.Errorf("chain filter shutting down")
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}
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}
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// FilteredBlocks returns the channel that filtered blocks are to be sent over.
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// Each time a block is connected to the end of a main chain, and appropriate
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// FilteredBlock which contains the transactions which mutate our watched UTXO
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// set is to be returned.
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//
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) FilteredBlocks() <-chan *FilteredBlock {
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return c.newBlocks
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}
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// DisconnectedBlocks returns a receive only channel which will be sent upon
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// with the empty filtered blocks of blocks which are disconnected from the
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// main chain in the case of a re-org.
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//
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// NOTE: This is part of the FilteredChainView interface.
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func (c *CfFilteredChainView) DisconnectedBlocks() <-chan *FilteredBlock {
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return c.staleBlocks
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}
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