refactor: rewrite getBlocks batch loop to be clearer

This commit was moved from ipfs/go-blockservice@30ca6aa

blockservice/blockservice.go

@@ -333,23 +333,22 @@ func getBlocks(ctx context.Context, ks []cid.Cid, bs blockstore.Blockstore, fget
  return
  }
 
- for b := range rblocks {
- // batch available blocks together
- batch := make([]blocks.Block, 0, 8)
- batch = append(batch, b)
- logger.Debugf("BlockService.BlockFetched %s", b.Cid())
-
+ // batch available blocks together
+ const batchSize = 32
+ batch := make([]blocks.Block, 0, batchSize)
+ for {
+ var noMoreBlocks bool
  batchLoop:
- for {
+ for len(batch) < batchSize {
  select {
- case moreBlock, ok := <-rblocks:
+ case b, ok := <-rblocks:
  if !ok {
- // rblock has been closed, we set it to nil to avoid pulling zero values
- rblocks = nil
- } else {
- logger.Debugf("BlockService.BlockFetched %s", moreBlock.Cid())
- batch = append(batch, moreBlock)
+ noMoreBlocks = true
+ break batchLoop
  }
+
+ logger.Debugf("BlockService.BlockFetched %s", b.Cid())
+ batch = append(batch, b)
  case <-ctx.Done():
  return
  default:
@@ -370,13 +369,17 @@ func getBlocks(ctx context.Context, ks []cid.Cid, bs blockstore.Blockstore, fget
  return
  }
 
- for _, b = range batch {
+ for _, b := range batch {
  select {
  case out <- b:
  case <-ctx.Done():
  return
  }
  }
+ batch = batch[:0]
+ if noMoreBlocks {
+ break
+ }
  }
  }()
  return out