snarkos-storage 2.0.2

// Copyright (C) 2019-2022 Aleo Systems Inc.
// This file is part of the snarkOS library.

// The snarkOS library is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// The snarkOS library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with the snarkOS library. If not, see <https://www.gnu.org/licenses/>.

use super::*;

/// An iterator over the keys of a prefix.
pub struct Keys<'a, K> {
    db_iter: rocksdb::DBRawIterator<'a>,
    prefix: Vec<u8>,
    _phantom: PhantomData<K>,
}

impl<'a, K: DeserializeOwned> Keys<'a, K> {
    pub(crate) fn new(db_iter: rocksdb::DBRawIterator<'a>, prefix: Vec<u8>) -> Self {
        Self {
            db_iter,
            prefix,
            _phantom: PhantomData,
        }
    }
}

impl<'a, K: DeserializeOwned> Iterator for Keys<'a, K> {
    type Item = K;

    fn next(&mut self) -> Option<Self::Item> {
        if self.db_iter.valid() {
            let key = match self
                .db_iter
                .key()
                .and_then(|k| if k.starts_with(&self.prefix) { Some(k) } else { None })
                .map(|k| bincode::deserialize(&k[self.prefix.len()..]).ok())
            {
                Some(key) => key,
                None => None,
            };

            self.db_iter.next();
            key
        } else {
            None
        }
    }
}