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merge.go
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merge.go
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package syncer
import (
"context"
"errors"
"fmt"
"github.com/oasisprotocol/oasis-core/go/storage/mkvs/node"
)
type SubtreeMerger struct {
}
// MergeVerifiedSubtree merges a previously verified subtree with an
// existing tree.
func (m *SubtreeMerger) MergeVerifiedSubtree(
ctx context.Context,
dst *node.Pointer,
subtree *node.Pointer,
committer func(*node.Pointer) error,
) error {
if dst == nil || subtree == nil {
return nil
}
if !dst.Clean {
// TODO: Support merging into non-clean subtrees. If a subtree
// is not clean, this means that the tree structure may
// be changed.
return errors.New("merger: merging into non-clean subtree not yet supported")
}
// If the destination pointer is clean, sanity check that we are
// merging correct nodes.
if !dst.Hash.Equal(&subtree.Hash) {
return fmt.Errorf("merger: hash mismatch during merge (expected: %s got: %s)",
dst.Hash,
subtree.Hash,
)
}
// If the subtree node is nil, there is nothing more to merge.
if subtree.Node == nil {
return nil
}
// If destination node is nil, we can simply replace the whole subtree.
if dst.Node == nil {
dst.Node = subtree.Node
if err := committer(dst); err != nil {
return err
}
return nil
}
switch n := dst.Node.(type) {
case *node.InternalNode:
// This should be safe due to the hash sanity check above.
sn := subtree.Node.(*node.InternalNode)
// Proceed with merging children.
if err := m.MergeVerifiedSubtree(ctx, n.Left, sn.Left, committer); err != nil {
return err
}
if err := m.MergeVerifiedSubtree(ctx, n.Right, sn.Right, committer); err != nil {
return err
}
case *node.LeafNode:
// This should be safe due to the hash sanity check above.
_ = subtree.Node.(*node.LeafNode)
// Clean leaf nodes do not need to be touched as they are the same.
}
return nil
}