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use super::*;
use std::iter;
#[derive(Debug)]
pub struct Pager {
pub page_size: usize,
pub pages: Vec<Option<Page>>,
length: usize,
}
impl Pager {
pub fn new(page_size: usize) -> Self {
Pager {
page_size,
length: 0,
pages: vec![None; 16],
}
}
pub fn with_pages(page_size: usize, pages: Vec<Option<Page>>) -> Self {
for page in &pages {
if let Some(ref page) = *page {
assert_eq!(page.len(), page_size);
}
}
Pager {
page_size,
length: pages.len(),
pages,
}
}
pub fn get_mut_or_alloc(&mut self, page_num: usize) -> &mut Page {
if page_num >= self.pages.len() {
self.grow_pages(page_num);
}
if self.pages[page_num].is_none() {
let buf = vec![0; self.page_size];
let page = Page::new(page_num, buf);
self.pages[page_num] = Some(page);
}
if page_num > self.length {
self.length = page_num + 1;
}
self.pages[page_num].as_mut().unwrap()
}
pub fn get(&self, page_num: usize) -> Option<&Page> {
match self.pages.get(page_num) {
None => None,
Some(page) => page.as_ref(),
}
}
pub fn get_mut(&mut self, page_num: usize) -> Option<&mut Page> {
match self.pages.get_mut(page_num) {
None => None,
Some(page) => page.as_mut(),
}
}
fn grow_pages(&mut self, index: usize) {
let start_len = self.pages.len();
let mut new_len = start_len * 2;
if new_len == 0 {
new_len += 1
}
while new_len <= index {
new_len *= 2;
}
self.pages.resize(new_len, None);
}
#[inline]
pub fn len(&self) -> usize {
self.length
}
#[inline]
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn iter(&self) -> Iter {
Iter {
inner: &self,
cursor: 0,
}
}
}
impl Default for Pager {
fn default() -> Self {
Pager::new(1024)
}
}
pub struct Iter<'a> {
inner: &'a Pager,
cursor: usize,
}
impl<'a> iter::Iterator for Iter<'a> {
type Item = &'a Option<Page>;
fn next(&mut self) -> Option<Self::Item> {
let cursor = self.cursor;
self.cursor += 1;
if cursor >= self.inner.len() {
None
} else {
self.inner.pages.get(cursor)
}
}
}