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use std::{
sync::{
Arc
},
ops::{
Deref
}
};
#[derive(Debug)]
pub struct CowArc<T: Clone>{
inner: Arc<T>
}
impl<T: Clone> CowArc<T> {
pub fn new(val: T) -> CowArc<T>{
CowArc{
inner: Arc::new(val)
}
}
pub fn set_val(&mut self, val: T){
self.inner = Arc::new(val);
}
pub fn update_val<F: FnOnce(&mut T)>(&mut self, f: F) {
let mut v: T = self.inner.deref().clone();
f(&mut v);
self.inner = Arc::new(v);
}
}
impl<T: Clone> Deref for CowArc<T>{
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.deref()
}
}
impl<T: Clone> Clone for CowArc<T>{
fn clone(&self) -> Self {
CowArc{
inner: self.inner.clone()
}
}
}
#[cfg(test)]
mod tests{
use super::*;
#[test]
fn test_cow_arc(){
{
let test_str = "Test string";
let new_val_str = "New value";
let source = CowArc::new(test_str.to_owned());
let cloned = source.clone();
let mut changed = cloned.clone();
changed.set_val(new_val_str.to_owned());
let changed_cloned = changed.clone();
let source_ptr: &String = source.deref();
let cloned_ptr: &String = cloned.deref();
let changed_ptr: &String = changed.deref();
let changed_cloned_ptr: &String = changed_cloned.deref();
assert!(std::ptr::eq(source_ptr, cloned_ptr));
assert!(std::ptr::eq(source_ptr, changed_ptr) == false);
assert!(std::ptr::eq(changed_ptr, changed_cloned_ptr));
assert!(cloned_ptr.eq(test_str));
assert!(changed.eq(new_val_str));
}
{
let source = CowArc::new(vec![1, 2, 3]);
let cloned = source.clone();
let mut changed = cloned.clone();
changed.set_val(vec![1, 2, 3, 4]);
let changed_cloned = changed.clone();
let mut updated = changed_cloned.clone();
updated.update_val(|val|{
val.push(5);
});
let source_ptr: &Vec<i32> = source.deref();
let cloned_ptr: &Vec<i32> = cloned.deref();
let changed_ptr: &Vec<i32> = changed.deref();
let changed_cloned_ptr: &Vec<i32> = changed_cloned.deref();
let updated_ptr: &Vec<i32> = updated.deref();
assert!(std::ptr::eq(source_ptr, cloned_ptr));
assert!(std::ptr::eq(source_ptr, changed_ptr) == false);
assert!(std::ptr::eq(changed_ptr, changed_cloned_ptr));
assert!(std::ptr::eq(changed_ptr, updated_ptr) == false);
assert!(changed.eq(&vec![1, 2, 3, 4]));
assert!(updated.eq(&vec![1, 2, 3, 4, 5]));
}
}
}