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eth/downloader: dereference discarded statesync request #15545

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fjl merged 1 commit into from
Jan 2, 2018
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eth/downloader: dereference discarded statesync request #15545

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5 changes: 4 additions & 1 deletion eth/downloader/statesync.go
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Original file line number Diff line number Diff line change
Expand Up @@ -132,7 +132,10 @@ func (d *Downloader) runStateSync(s *stateSync) *stateSync {

// Send the next finished request to the current sync:
case deliverReqCh <- deliverReq:
finished = append(finished[:0], finished[1:]...)
// Shift out the first request, but also set the emptied slot to nil for GC
copy(finished, finished[1:])
finished[len(finished)-1] = nil
finished = finished[:len(finished)-1]
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@fjl fjl Nov 27, 2017

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You can get the same effect using

finished = append(finished[:0:len(finished)-1], finished[1:]...)

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@karalabe karalabe Dec 21, 2017

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Actually, this full format seems to reduce the capacity too, meaning it would be a reallocation of the underlying buffer. Am I missing something?

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@fjl fjl Dec 21, 2017 •
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I suggested this because I thought you want to avoid growing the slice indefinitely. The threeway slice expression does this.

If all you want is setting the unused element to nil, your solution is OK.

It's hard to decide, I want to keep the code compact. This operation isn't worth three lines + comment.


// Handle incoming state packs:
case pack := <-d.stateCh:
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