Make switchToSharding more efficient

hamt/hamt.go

@@ -229,6 +229,26 @@ func (ds *Shard) Set(ctx context.Context, name string, nd ipld.Node) error {
  return err
 }
 
+// Set sets 'name' = nd in the HAMT, using directly the information in the
+// given link. This avoids writing the given node, then reading it to making a
+// link out of it.
+func (ds *Shard) SetLink(ctx context.Context, name string, lnk *ipld.Link) error {
+ hv := newHashBits(name)
+
+ newLink := ipld.Link{
+ Name: lnk.Name,
+ Size: lnk.Size,
+ Cid: lnk.Cid,
+ }
+
+ // FIXME: We don't need to set the name here, it will get overwritten.
+ // This is confusing, confirm and remove this line.
+ newLink.Name = ds.linkNamePrefix(0) + name
+
+ _, err := ds.swapValue(ctx, hv, name, &newLink)
+ return err
+}
+
 // Swap sets a link pointing to the passed node as the value under the
 // name key in this Shard or its children. It also returns the previous link
 // under that name key (if any).

io/directory.go

@@ -334,12 +334,7 @@ func (d *BasicDirectory) switchToSharding(ctx context.Context) (*HAMTDirectory,
  hamtDir.shard = shard
 
  for _, lnk := range d.node.Links() {
- node, err := d.dserv.Get(ctx, lnk.Cid)
- if err != nil {
- return nil, err
- }
-
- err = hamtDir.shard.Set(ctx, lnk.Name, node)
+ err = hamtDir.shard.SetLink(ctx, lnk.Name, lnk)
  if err != nil {
  return nil, err
  }