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waiting_handler.go
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/
waiting_handler.go
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// (c) 2019-2022, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package peer
import (
"context"
"github.com/ava-labs/subnet-evm/plugin/evm/message"
)
var _ message.ResponseHandler = &waitingResponseHandler{}
// waitingResponseHandler implements the ResponseHandler interface
// Internally used to wait for response after making a request synchronously
// responseChan may contain response bytes if the original request has not failed
// responseChan is closed in either fail or success scenario
type waitingResponseHandler struct {
responseChan chan []byte // blocking channel with response bytes
failed bool // whether the original request is failed
}
// newWaitingResponseHandler returns new instance of the waitingResponseHandler
func newWaitingResponseHandler() *waitingResponseHandler {
return &waitingResponseHandler{
// Make buffer length 1 so that OnResponse can complete
// even if no goroutine is waiting on the channel (i.e.
// the context of a request is cancelled.)
responseChan: make(chan []byte, 1),
}
}
// OnResponse passes the response bytes to the responseChan and closes the channel
func (w *waitingResponseHandler) OnResponse(response []byte) error {
w.responseChan <- response
close(w.responseChan)
return nil
}
// OnFailure sets the failed flag to true and closes the channel
func (w *waitingResponseHandler) OnFailure() error {
w.failed = true
close(w.responseChan)
return nil
}
func (waitingHandler *waitingResponseHandler) WaitForResult(ctx context.Context) ([]byte, error) {
select {
case <-ctx.Done():
return nil, ctx.Err()
case response := <-waitingHandler.responseChan:
if waitingHandler.failed {
return nil, ErrRequestFailed
}
return response, nil
}
}