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|
/// Wrapper around Vec which supports fast indexing and rotation
///
/// The rotation implemented by grid::Storage is a simple integer addition.
/// Compare with standard library rotation which requires rearranging items in
/// memory.
///
/// As a consequence, the indexing operators need to be reimplemented for this
/// type to account for the 0th element not always being at the start of the
/// allocation.
///
/// Because certain Vec operations are no longer valid on this type, no Deref
/// implementation is provided. Anything from Vec that should be exposed must be
/// done so manually.
use std::ops::{Index, IndexMut};
#[derive(Clone, Debug, Deserialize, Serialize, Eq, PartialEq)]
pub struct Storage<T> {
inner: Vec<T>,
zero: usize,
}
impl<T> Storage<T> {
#[inline]
pub fn with_capacity(cap: usize) -> Storage<T> {
Storage {
inner: Vec::with_capacity(cap),
zero: 0
}
}
#[inline]
pub fn push(&mut self, item: T) {
self.inner.push(item)
}
#[inline]
pub fn pop(&mut self) -> Option<T> {
self.inner.pop()
}
#[inline]
pub fn len(&self) -> usize {
self.inner.len()
}
/// Compute actual index in underlying storage given the requested index.
#[inline]
fn compute_index(&self, requested: usize) -> usize {
(requested + self.zero) % self.len()
}
pub fn swap(&mut self, a: usize, b: usize) {
let a = self.compute_index(a);
let b = self.compute_index(b);
self.inner.swap(a, b);
}
pub fn iter(&self) -> Iter<T> {
Iter { storage: self, index: 0 }
}
pub fn iter_mut(&mut self) -> IterMut<T> {
IterMut { storage: self, index: 0 }
}
pub fn rotate(&mut self, count: isize) {
let len = self.len();
assert!(count.abs() as usize <= len);
self.zero += (count + len as isize) as usize % len;
}
}
impl<T> Index<usize> for Storage<T> {
type Output = T;
#[inline]
fn index(&self, index: usize) -> &T {
let index = self.compute_index(index); // borrowck
&self.inner[index]
}
}
impl<T> IndexMut<usize> for Storage<T> {
#[inline]
fn index_mut(&mut self, index: usize) -> &mut T {
let index = self.compute_index(index); // borrowck
&mut self.inner[index]
}
}
pub struct Iter<'a, T: 'a> {
storage: &'a Storage<T>,
index: usize,
}
pub struct IterMut<'a, T: 'a> {
storage: &'a mut Storage<T>,
index: usize,
}
impl<'a, T: 'a> Iterator for Iter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
if self.index == self.storage.len() {
None
} else {
let res = Some(&self.storage[self.index]);
self.index += 1;
res
}
}
}
impl<'a, T: 'a> Iterator for IterMut<'a, T> {
type Item = &'a mut T;
fn next(&mut self) -> Option<Self::Item> {
if self.index == self.storage.len() {
None
} else {
let index = self.index;
self.index += 1;
unsafe {
Some(&mut *(&mut self.storage[index] as *mut _))
}
}
}
}
|
