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use std::clone::Clone;
use super::wrapping_number::{sequence_greater_than, sequence_less_than};
pub type SequenceNumber = u16;
#[derive(Debug)]
pub struct SequenceBuffer<T: Clone> {
sequence_num: SequenceNumber,
entry_sequences: Box<[Option<SequenceNumber>]>,
entries: Box<[Option<T>]>,
}
impl<T: Clone> SequenceBuffer<T> {
pub fn with_capacity(size: u16) -> Self {
Self {
sequence_num: 0,
entry_sequences: vec![None; size as usize].into_boxed_slice(),
entries: vec![None; size as usize].into_boxed_slice(),
}
}
pub fn sequence_num(&self) -> SequenceNumber {
self.sequence_num
}
pub fn get_mut(&mut self, sequence_num: SequenceNumber) -> Option<&mut T> {
if self.exists(sequence_num) {
let index = self.index(sequence_num);
return self.entries[index].as_mut();
}
None
}
pub fn get(&self, sequence_num: SequenceNumber) -> Option<&T> {
if self.exists(sequence_num) {
let index = self.index(sequence_num);
return self.entries[index].as_ref();
}
None
}
pub fn insert(&mut self, sequence_num: SequenceNumber, entry: T) -> bool {
if sequence_less_than(
sequence_num,
self.sequence_num
.wrapping_sub(self.entry_sequences.len() as u16),
) {
return false;
}
self.advance_sequence(sequence_num);
let index = self.index(sequence_num);
self.entry_sequences[index] = Some(sequence_num);
self.entries[index] = Some(entry);
return true;
}
pub fn exists(&self, sequence_num: SequenceNumber) -> bool {
let index = self.index(sequence_num);
if let Some(s) = self.entry_sequences[index] {
return s == sequence_num;
}
false
}
pub fn remove(&mut self, sequence_num: SequenceNumber) -> Option<T> {
if self.exists(sequence_num) {
let index = self.index(sequence_num);
let value = std::mem::replace(&mut self.entries[index], None);
self.entry_sequences[index] = None;
return value;
}
None
}
fn advance_sequence(&mut self, sequence_num: SequenceNumber) {
if sequence_greater_than(sequence_num.wrapping_add(1), self.sequence_num) {
self.remove_entries(u32::from(sequence_num));
self.sequence_num = sequence_num.wrapping_add(1);
}
}
fn remove_entries(&mut self, mut finish_sequence: u32) {
let start_sequence = u32::from(self.sequence_num);
if finish_sequence < start_sequence {
finish_sequence += 65536;
}
if finish_sequence - start_sequence < self.entry_sequences.len() as u32 {
for sequence in start_sequence..=finish_sequence {
self.remove(sequence as u16);
}
} else {
for index in 0..self.entry_sequences.len() {
self.entries[index] = None;
self.entry_sequences[index] = None;
}
}
}
fn index(&self, sequence: SequenceNumber) -> usize {
sequence as usize % self.entry_sequences.len()
}
pub fn oldest(&self) -> u16 {
return self
.sequence_num
.wrapping_sub(self.entry_sequences.len() as u16);
}
pub fn clear(&mut self) {
let size = self.entry_sequences.len();
self.sequence_num = 0;
self.entry_sequences = vec![None; size].into_boxed_slice();
self.entries = vec![None; size].into_boxed_slice();
}
pub fn remove_until(&mut self, finish_sequence: u16) {
let oldest = self.oldest();
for seq in oldest..finish_sequence {
self.remove(seq);
}
}
pub fn get_entries_count(&self) -> u8 {
let mut count = 0;
let mut seq = self.oldest();
loop {
if self.exists(seq) {
count += 1;
}
seq = seq.wrapping_add(1);
if seq == self.sequence_num {
break;
}
}
return count;
}
pub fn iter(&self, reverse: bool) -> SequenceIterator<T> {
let index = {
if reverse {
self.sequence_num
} else {
self.oldest()
}
};
return SequenceIterator::new(self, index, self.entry_sequences.len(), reverse);
}
}
pub struct SequenceIterator<'s, T>
where
T: 's + Clone,
{
buffer: &'s SequenceBuffer<T>,
index: u16,
count: usize,
reverse: bool,
}
impl<'s, T: Clone> SequenceIterator<'s, T> {
pub fn new(
seq_buf: &'s SequenceBuffer<T>,
start: u16,
count: usize,
reverse: bool,
) -> SequenceIterator<'s, T> {
SequenceIterator::<T> {
buffer: seq_buf,
index: start,
count,
reverse,
}
}
pub fn next(&mut self) -> Option<(SequenceNumber, &'s T)> {
loop {
if self.count == 0 {
return None;
}
let current_item = self.buffer.get(self.index);
let current_index = self.index;
if self.reverse {
self.index = self.index.wrapping_sub(1);
} else {
self.index = self.index.wrapping_add(1);
}
self.count -= 1;
if let Some(item) = current_item {
return Some((current_index, item));
}
}
}
}