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use hash_db::HashDBRef;
use nibble::NibbleSlice;
use node::Node;
use node_codec::NodeCodec;
use super::{DBValue, Result, TrieError, Query, TrieLayout, CError, TrieHash};
#[cfg(not(feature = "std"))]
use alloc::boxed::Box;
pub struct Lookup<'a, L: TrieLayout, Q: Query<L::Hash>> {
pub db: &'a dyn HashDBRef<L::Hash, DBValue>,
pub query: Q,
pub hash: TrieHash<L>,
}
impl<'a, L, Q> Lookup<'a, L, Q>
where
L: TrieLayout,
Q: Query<L::Hash>,
{
pub fn look_up(
mut self,
key: NibbleSlice,
) -> Result<Option<Q::Item>, TrieHash<L>, CError<L>> {
let mut partial = key;
let mut hash = self.hash;
let mut key_nibbles = 0;
for depth in 0.. {
let node_data = match self.db.get(&hash, key.mid(key_nibbles).left()) {
Some(value) => value,
None => return Err(Box::new(match depth {
0 => TrieError::InvalidStateRoot(hash),
_ => TrieError::IncompleteDatabase(hash),
})),
};
self.query.record(&hash, &node_data, depth);
let mut node_data = &node_data[..];
loop {
let decoded = match L::Codec::decode(node_data) {
Ok(node) => node,
Err(e) => {
return Err(Box::new(TrieError::DecoderError(hash, e)))
}
};
match decoded {
Node::Leaf(slice, value) => {
return Ok(match slice == partial {
true => Some(self.query.decode(value)),
false => None,
})
}
Node::Extension(slice, item) => {
if partial.starts_with(&slice) {
node_data = item;
partial = partial.mid(slice.len());
key_nibbles += slice.len();
} else {
return Ok(None)
}
}
Node::Branch(children, value) => match partial.is_empty() {
true => return Ok(value.map(move |val| self.query.decode(val))),
false => match children[partial.at(0) as usize] {
Some(x) => {
node_data = x;
partial = partial.mid(1);
key_nibbles += 1;
}
None => return Ok(None)
}
},
Node::NibbledBranch(slice, children, value) => {
if !partial.starts_with(&slice) {
return Ok(None)
}
match partial.len() == slice.len() {
true => return Ok(value.map(move |val| self.query.decode(val))),
false => match children[partial.at(slice.len()) as usize] {
Some(x) => {
node_data = x;
partial = partial.mid(slice.len() + 1);
key_nibbles += slice.len() + 1;
}
None => return Ok(None)
}
}
},
Node::Empty => return Ok(None),
}
if let Some(h) = L::Codec::try_decode_hash(&node_data) {
hash = h;
break
}
}
}
Ok(None)
}
}