The state availability is checked during the creation of a state reader.
- In hash-based database, if the specified root node does not exist on disk disk, then
the state reader won't be created and an error will be returned.
- In path-based database, if the specified state layer is not available, then the
state reader won't be created and an error will be returned.
This change also contains a stricter semantics regarding the `Commit` operation: once it has been performed, the trie is no longer usable, and certain operations will return an error.
In this PR, all TryXXX(e.g. TryGet) APIs of trie are renamed to XXX(e.g. Get) with an error returned.
The original XXX(e.g. Get) APIs are renamed to MustXXX(e.g. MustGet) and does not return any error -- they print a log output. A future PR will change the behaviour to panic on errorrs.
* ethdb: remove Set
Set deadlocks immediately and isn't part of the Database interface.
* trie: add Err to Iterator
This is useful for testing because the underlying NodeIterator doesn't
need to be kept in a separate variable just to get the error.
* trie: add LeafKey to iterator, panic when not at leaf
LeafKey is useful for callers that can't interpret Path.
* trie: retry failed seek/peek in iterator Next
Instead of failing iteration irrecoverably, make it so Next retries the
pending seek or peek every time.
Smaller changes in this commit make this easier to test:
* The iterator previously returned from Next on encountering a hash
node. This caused it to visit the same path twice.
* Path returned nibbles with terminator symbol for valueNode attached
to fullNode, but removed it for valueNode attached to shortNode. Now
the terminator is always present. This makes Path unique to each node
and simplifies Leaf.
* trie: add Path to MissingNodeError
The light client trie iterator needs to know the path of the node that's
missing so it can retrieve a proof for it. NodeIterator.Path is not
sufficient because it is updated when the node is resolved and actually
visited by the iterator.
Also remove unused fields. They were added a long time ago before we
knew which fields would be needed for the light client.
The key was constructed from nibbles, which isn't possible for all
nodes. Remove the only use of Key in LightTrie by always retrying with
the original key that was looked up.
