1use std::{
 2    borrow::Cow,
 3    fmt::{self, Debug},
 4    sync::Arc,
 5};
 6
 7#[derive(PartialEq, Eq)]
 8pub enum ArcCow<'a, T: ?Sized> {
 9    Borrowed(&'a T),
10    Owned(Arc<T>),
11}
12
13use std::hash::{Hash, Hasher};
14
15impl<'a, T: ?Sized + Hash> Hash for ArcCow<'a, T> {
16    fn hash<H: Hasher>(&self, state: &mut H) {
17        match self {
18            Self::Borrowed(borrowed) => Hash::hash(borrowed, state),
19            Self::Owned(owned) => Hash::hash(&**owned, state),
20        }
21    }
22}
23
24impl<'a, T: ?Sized> Clone for ArcCow<'a, T> {
25    fn clone(&self) -> Self {
26        match self {
27            Self::Borrowed(borrowed) => Self::Borrowed(borrowed),
28            Self::Owned(owned) => Self::Owned(owned.clone()),
29        }
30    }
31}
32
33impl<'a, T: ?Sized> From<&'a T> for ArcCow<'a, T> {
34    fn from(s: &'a T) -> Self {
35        Self::Borrowed(s)
36    }
37}
38
39impl<T> From<Arc<T>> for ArcCow<'_, T> {
40    fn from(s: Arc<T>) -> Self {
41        Self::Owned(s)
42    }
43}
44
45impl From<String> for ArcCow<'_, str> {
46    fn from(value: String) -> Self {
47        Self::Owned(value.into())
48    }
49}
50
51impl<'a> From<Cow<'a, str>> for ArcCow<'a, str> {
52    fn from(value: Cow<'a, str>) -> Self {
53        match value {
54            Cow::Borrowed(borrowed) => Self::Borrowed(borrowed),
55            Cow::Owned(owned) => Self::Owned(owned.into()),
56        }
57    }
58}
59
60impl<'a, T: ?Sized + ToOwned> std::borrow::Borrow<T> for ArcCow<'a, T> {
61    fn borrow(&self) -> &T {
62        match self {
63            ArcCow::Borrowed(borrowed) => borrowed,
64            ArcCow::Owned(owned) => owned.as_ref(),
65        }
66    }
67}
68
69impl<T: ?Sized> std::ops::Deref for ArcCow<'_, T> {
70    type Target = T;
71
72    fn deref(&self) -> &Self::Target {
73        match self {
74            ArcCow::Borrowed(s) => s,
75            ArcCow::Owned(s) => s.as_ref(),
76        }
77    }
78}
79
80impl<T: ?Sized> AsRef<T> for ArcCow<'_, T> {
81    fn as_ref(&self) -> &T {
82        match self {
83            ArcCow::Borrowed(borrowed) => borrowed,
84            ArcCow::Owned(owned) => owned.as_ref(),
85        }
86    }
87}
88
89impl<'a, T: ?Sized + Debug> Debug for ArcCow<'a, T> {
90    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
91        match self {
92            ArcCow::Borrowed(borrowed) => Debug::fmt(borrowed, f),
93            ArcCow::Owned(owned) => Debug::fmt(&**owned, f),
94        }
95    }
96}