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use hashdb::HashDB;
use nibbleslice::NibbleSlice;
use rlp::{Rlp, View};
use ::{H256};
use super::{TrieError, Query};
use super::node::Node;
pub struct Lookup<'a, Q: Query> {
pub db: &'a HashDB,
pub query: Q,
pub hash: H256,
}
impl<'a, Q: Query> Lookup<'a, Q> {
pub fn look_up(mut self, mut key: NibbleSlice) -> super::Result<Option<Q::Item>> {
let mut hash = self.hash;
for depth in 0.. {
let node_data = match self.db.get(&hash) {
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 {
match Node::decoded(node_data) {
Node::Leaf(slice, value) => {
return Ok(match slice == key {
true => Some(self.query.decode(value)),
false => None,
})
}
Node::Extension(slice, item) => {
if key.starts_with(&slice) {
node_data = item;
key = key.mid(slice.len());
} else {
return Ok(None)
}
}
Node::Branch(children, value) => match key.is_empty() {
true => return Ok(value.map(move |val| self.query.decode(val))),
false => {
node_data = children[key.at(0) as usize];
key = key.mid(1);
}
},
_ => return Ok(None),
}
let r = Rlp::new(node_data);
if r.is_data() && r.size() == 32 {
hash = r.as_val();
break
}
}
}
Ok(None)
}
}