mirror of https://github.com/ethereum/go-ethereum
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// Copyright 2023 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 ethclient |
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import ( |
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"context" |
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"sync" |
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"time" |
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"github.com/ethereum/go-ethereum" |
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"github.com/ethereum/go-ethereum/core/types" |
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"github.com/ethereum/go-ethereum/event" |
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"github.com/ethereum/go-ethereum/rpc" |
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) |
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// subscribeNewHeadPolling creates a block filter and polls it.
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// This is the fallback for SubscribeNewHead on HTTP connections.
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func (ec *Client) subscribeNewHeadPolling(ctx context.Context, ch chan<- *types.Header) (event.Subscription, error) { |
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var id string |
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err := ec.c.CallContext(ctx, &id, "eth_newBlockFilter") |
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if err != nil { |
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return nil, err |
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} |
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sub := newFilterSub(ec.c, id, ch) |
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return sub, nil |
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} |
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// subscribeFilterLogs subscribes to a log filter.
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// This is the fallback for SubscribeFilterLogs on HTTP connections.
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func (ec *Client) subscribeFilterLogsPolling(ctx context.Context, q ethereum.FilterQuery, ch chan<- types.Log) (ethereum.Subscription, error) { |
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arg, err := toFilterArg(q) |
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if err != nil { |
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return nil, err |
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} |
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var id string |
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err = ec.c.CallContext(ctx, &id, "eth_newFilter", arg) |
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if err != nil { |
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return nil, err |
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} |
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sub := newFilterSub(ec.c, id, ch) |
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return sub, nil |
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} |
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// filterSub implements event.Subscription with the polling filter API.
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type filterSub[Result any] struct { |
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// The channel to send the results to
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resultc chan<- Result |
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errc chan error |
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closed chan struct{} |
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unsubOnce sync.Once |
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id string |
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client *rpc.Client |
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} |
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func newFilterSub[Result any](client *rpc.Client, id string, resultc chan<- Result) *filterSub[Result] { |
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sub := &filterSub[Result]{ |
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resultc: resultc, |
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errc: make(chan error, 1), |
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closed: make(chan struct{}), |
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client: client, |
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} |
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go sub.poll() |
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return sub |
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} |
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// Unsubscribe cancels the event subscription.
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func (s *filterSub[Result]) Unsubscribe() { |
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s.closeWithError(nil) |
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} |
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// Err returns the subscription error channel.
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func (s *filterSub[Result]) Err() <-chan error { |
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return s.errc |
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} |
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func (s *filterSub[Result]) poll() { |
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var timer = time.NewTicker(10 * time.Second) |
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for { |
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err := s.getChanges() |
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if err != nil { |
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s.closeWithError(err) |
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return |
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} |
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// Wait for next time.
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select { |
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case <-timer.C: |
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case <-s.closed: |
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return |
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} |
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} |
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} |
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func (s *filterSub[Result]) closeWithError(err error) { |
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s.unsubOnce.Do(func() { |
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close(s.closed) |
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unsubErr := s.uninstallFilter() |
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if unsubErr != nil && err == nil { |
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err = unsubErr |
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} |
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if err != nil { |
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select { |
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case s.errc <- err: |
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default: |
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} |
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} |
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close(s.errc) |
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}) |
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} |
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// getChanges calls eth_getFilterChanges and delivers the results.
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func (s *filterSub[Result]) getChanges() error { |
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ctx, done := context.WithTimeout(context.Background(), 10*time.Second) |
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defer done() |
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var results []Result |
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err := s.client.CallContext(ctx, &results, "eth_getFilterChanges", s.id) |
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if err != nil { |
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return err |
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} |
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for _, result := range results { |
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select { |
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case s.resultc <- result: |
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case <-s.closed: |
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return nil |
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} |
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} |
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return nil |
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} |
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// uninstallFilter removes the filter on the server side.
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func (s *filterSub[Result]) uninstallFilter() error { |
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ctx, done := context.WithTimeout(context.Background(), 10*time.Second) |
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defer done() |
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return s.client.CallContext(ctx, nil, "eth_uninstallFilter", s.id) |
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} |
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