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use core::mem;
use crate::common::segment_iterator::SegmentIterator;
use crate::Segment;
pub struct SegmentsSlice<'a, TSegment> {
slice: &'a mut [TSegment],
number_of_bytes: usize,
pos: usize,
single_index: Option<usize>,
}
impl<'a, TSegment> SegmentsSlice<'a, TSegment>
where
TSegment: Segment,
{
#[inline]
pub fn new(slice: &'a mut [TSegment]) -> Self {
let mut number_of_bytes = 0;
let mut no_item_yet = true;
let mut single_index = None;
for (index, item) in slice.iter().enumerate() {
let item_len = item.number_of_bytes();
if item_len > 0 {
number_of_bytes += item_len;
if no_item_yet {
single_index = Some(index);
no_item_yet = false;
} else {
single_index = None;
}
}
}
Self {
slice,
number_of_bytes,
pos: 0,
single_index,
}
}
#[inline]
fn remaining(&self) -> usize {
let len = self.slice.len();
if self.pos < len {
len - self.pos
} else {
0
}
}
fn take(&mut self, index: usize) -> Option<TSegment> {
if index < self.slice.len() {
let empty = TSegment::empty();
Some(mem::replace(&mut self.slice[index], empty))
} else {
None
}
}
}
impl<'a, TSegment> SegmentIterator<TSegment> for SegmentsSlice<'a, TSegment>
where
TSegment: Segment,
{
fn exact_number_of_bytes(&self) -> Option<usize> {
Some(self.number_of_bytes)
}
fn is_empty(&self) -> bool {
self.number_of_bytes == 0
}
fn single(mut self) -> Result<TSegment, Self>
where
Self: Sized,
{
if let Some(single_index) = self.single_index {
let taken = SegmentsSlice::take(&mut self, single_index);
Ok(taken.expect("Implementation error (single_index is invalid)"))
} else {
Err(self)
}
}
}
impl<'a, TSegment: Segment> Iterator for SegmentsSlice<'a, TSegment> {
type Item = TSegment;
fn next(&mut self) -> Option<Self::Item> {
let item = SegmentsSlice::take(self, self.pos);
self.pos += 1;
item
}
}
impl<'a, TSegment: Segment> ExactSizeIterator for SegmentsSlice<'a, TSegment> {
#[inline]
fn len(&self) -> usize {
self.remaining()
}
}