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use std::marker;
use crate::core::hash::{Hash, ZERO_HASH};
use crate::core::pmmr::{bintree_postorder_height, is_leaf, peaks, Backend};
use crate::ser::{PMMRIndexHashable, PMMRable};
pub struct RewindablePMMR<'a, T, B>
where
T: PMMRable,
B: Backend<T>,
{
last_pos: u64,
backend: &'a B,
_marker: marker::PhantomData<T>,
}
impl<'a, T, B> RewindablePMMR<'a, T, B>
where
T: PMMRable,
B: 'a + Backend<T>,
{
pub fn new(backend: &'a B) -> RewindablePMMR<'_, T, B> {
RewindablePMMR {
backend,
last_pos: 0,
_marker: marker::PhantomData,
}
}
pub fn backend(&'a self) -> &Backend<T> {
self.backend
}
pub fn at(backend: &'a B, last_pos: u64) -> RewindablePMMR<'_, T, B> {
RewindablePMMR {
backend,
last_pos,
_marker: marker::PhantomData,
}
}
pub fn rewind(&mut self, position: u64) -> Result<(), String> {
let mut pos = position;
while bintree_postorder_height(pos + 1) > 0 {
pos += 1;
}
self.last_pos = pos;
Ok(())
}
pub fn get_data(&self, pos: u64) -> Option<T::E> {
if pos > self.last_pos {
None
} else if is_leaf(pos) {
self.backend.get_data(pos)
} else {
None
}
}
pub fn is_empty(&self) -> bool {
self.last_pos == 0
}
pub fn root(&self) -> Result<Hash, String> {
if self.is_empty() {
return Ok(ZERO_HASH);
}
let mut res = None;
for peak in self.peaks().iter().rev() {
res = match res {
None => Some(*peak),
Some(rhash) => Some((*peak, rhash).hash_with_index(self.unpruned_size())),
}
}
res.ok_or_else(|| "no root, invalid tree".to_owned())
}
pub fn peaks(&self) -> Vec<Hash> {
let peaks_pos = peaks(self.last_pos);
peaks_pos
.into_iter()
.filter_map(|pi| {
self.backend.get_from_file(pi)
})
.collect()
}
pub fn unpruned_size(&self) -> u64 {
self.last_pos
}
}