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readonly_pmmr.rs
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readonly_pmmr.rs
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// Copyright 2020 The Grin Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Readonly view of a PMMR.
use std::marker;
use crate::core::hash::Hash;
use crate::core::pmmr::pmmr::{bintree_rightmost, ReadablePMMR};
use crate::core::pmmr::{is_leaf, Backend};
use crate::ser::PMMRable;
/// Readonly view of a PMMR.
pub struct ReadonlyPMMR<'a, T, B>
where
T: PMMRable,
B: Backend<T>,
{
/// The last position in the PMMR
last_pos: u64,
/// The backend for this readonly PMMR
backend: &'a B,
// only needed to parameterise Backend
_marker: marker::PhantomData<T>,
}
impl<'a, T, B> ReadonlyPMMR<'a, T, B>
where
T: PMMRable,
B: 'a + Backend<T>,
{
/// Build a new readonly PMMR.
pub fn new(backend: &'a B) -> ReadonlyPMMR<'_, T, B> {
ReadonlyPMMR {
backend,
last_pos: 0,
_marker: marker::PhantomData,
}
}
/// Build a new readonly PMMR pre-initialized to
/// last_pos with the provided backend.
pub fn at(backend: &'a B, last_pos: u64) -> ReadonlyPMMR<'_, T, B> {
ReadonlyPMMR {
backend,
last_pos,
_marker: marker::PhantomData,
}
}
/// Helper function which returns un-pruned nodes from the insertion index
/// forward
/// returns last pmmr index returned along with data
pub fn elements_from_pmmr_index(
&self,
mut pmmr_index: u64,
max_count: u64,
max_pmmr_pos: Option<u64>,
) -> (u64, Vec<T::E>) {
let mut return_vec = vec![];
let last_pos = match max_pmmr_pos {
Some(p) => p,
None => self.last_pos,
};
if pmmr_index == 0 {
pmmr_index = 1;
}
while return_vec.len() < max_count as usize && pmmr_index <= last_pos {
if let Some(t) = self.get_data(pmmr_index) {
return_vec.push(t);
}
pmmr_index += 1;
}
(pmmr_index.saturating_sub(1), return_vec)
}
/// Helper function to get the last N nodes inserted, i.e. the last
/// n nodes along the bottom of the tree.
/// May return less than n items if the MMR has been pruned/compacted.
pub fn get_last_n_insertions(&self, n: u64) -> Vec<(Hash, T::E)> {
let mut return_vec = vec![];
let mut last_leaf = self.last_pos;
for _ in 0..n as u64 {
if last_leaf == 0 {
break;
}
last_leaf = bintree_rightmost(last_leaf);
if let Some(hash) = self.backend.get_hash(last_leaf) {
if let Some(data) = self.backend.get_data(last_leaf) {
return_vec.push((hash, data));
}
}
last_leaf -= 1;
}
return_vec
}
}
impl<'a, T, B> ReadablePMMR for ReadonlyPMMR<'a, T, B>
where
T: PMMRable,
B: 'a + Backend<T>,
{
type Item = T::E;
fn get_hash(&self, pos: u64) -> Option<Hash> {
if pos > self.last_pos {
None
} else if is_leaf(pos) {
// If we are a leaf then get hash from the backend.
self.backend.get_hash(pos)
} else {
// If we are not a leaf get hash ignoring the remove log.
self.backend.get_from_file(pos)
}
}
fn get_data(&self, pos: u64) -> Option<Self::Item> {
if pos > self.last_pos {
// If we are beyond the rhs of the MMR return None.
None
} else if is_leaf(pos) {
// If we are a leaf then get data from the backend.
self.backend.get_data(pos)
} else {
// If we are not a leaf then return None as only leaves have data.
None
}
}
fn get_from_file(&self, pos: u64) -> Option<Hash> {
if pos > self.last_pos {
None
} else {
self.backend.get_from_file(pos)
}
}
fn get_data_from_file(&self, pos: u64) -> Option<Self::Item> {
if pos > self.last_pos {
None
} else {
self.backend.get_data_from_file(pos)
}
}
fn unpruned_size(&self) -> u64 {
self.last_pos
}
fn leaf_pos_iter(&self) -> Box<dyn Iterator<Item = u64> + '_> {
self.backend.leaf_pos_iter()
}
fn leaf_idx_iter(&self, from_idx: u64) -> Box<dyn Iterator<Item = u64> + '_> {
self.backend.leaf_idx_iter(from_idx)
}
fn n_unpruned_leaves(&self) -> u64 {
self.backend.n_unpruned_leaves()
}
}