jiff/util/
borrow.rs

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1/*!
2This module re-exports a "dumb" version of `std::borrow::Cow`.
3
4It doesn't have any of the generic goodness and doesn't support dynamically
5sized types. It's just either a `T` or a `&T`.
6
7We have pretty simplistic needs, and we use this simpler type that works
8in core-only mode.
9*/
10
11#[derive(Clone, Debug)]
12pub(crate) enum DumbCow<'a, T> {
13    Owned(T),
14    Borrowed(&'a T),
15}
16
17impl<'a, T> DumbCow<'a, T> {
18    pub(crate) fn borrowed(&self) -> DumbCow<'_, T> {
19        match *self {
20            DumbCow::Owned(ref this) => DumbCow::Borrowed(this),
21            DumbCow::Borrowed(ref this) => DumbCow::Borrowed(this),
22        }
23    }
24}
25
26impl<'a, T> core::ops::Deref for DumbCow<'a, T> {
27    type Target = T;
28    fn deref(&self) -> &T {
29        match *self {
30            DumbCow::Owned(ref t) => t,
31            DumbCow::Borrowed(t) => t,
32        }
33    }
34}
35
36impl<'a, T: core::fmt::Display> core::fmt::Display for DumbCow<'a, T> {
37    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
38        core::fmt::Display::fmt(core::ops::Deref::deref(self), f)
39    }
40}
41
42/// A `Cow`, but can be used in core-only mode.
43///
44/// In core-only, the `Owned` variant doesn't exist.
45#[derive(Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
46pub(crate) enum StringCow<'a> {
47    #[cfg(feature = "alloc")]
48    Owned(alloc::string::String),
49    Borrowed(&'a str),
50}
51
52impl<'a> StringCow<'a> {
53    /// Returns this `String` or `&str` as a `&str`.
54    ///
55    /// Like `std::borrow::Cow`, the lifetime of the string slice returned
56    /// is tied to `StringCow`, and _not_ the original lifetime of the string
57    /// slice.
58    pub(crate) fn as_str<'s>(&'s self) -> &'s str {
59        match *self {
60            #[cfg(feature = "alloc")]
61            StringCow::Owned(ref s) => s,
62            StringCow::Borrowed(s) => s,
63        }
64    }
65
66    /// Converts this cow into an "owned" variant, copying if necessary.
67    ///
68    /// If this cow is already an "owned" variant, then this is a no-op.
69    #[cfg(feature = "alloc")]
70    pub(crate) fn into_owned(self) -> StringCow<'static> {
71        use alloc::string::ToString;
72
73        match self {
74            StringCow::Owned(string) => StringCow::Owned(string),
75            StringCow::Borrowed(string) => {
76                StringCow::Owned(string.to_string())
77            }
78        }
79    }
80}
81
82impl<'a> core::ops::Deref for StringCow<'a> {
83    type Target = str;
84    fn deref(&self) -> &str {
85        self.as_str()
86    }
87}
88
89impl<'a> core::fmt::Display for StringCow<'a> {
90    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
91        core::fmt::Display::fmt(self.as_str(), f)
92    }
93}
94
95#[cfg(feature = "alloc")]
96impl From<alloc::string::String> for StringCow<'static> {
97    fn from(string: alloc::string::String) -> StringCow<'static> {
98        StringCow::Owned(string)
99    }
100}
101
102impl<'a> From<&'a str> for StringCow<'a> {
103    fn from(string: &'a str) -> StringCow<'a> {
104        StringCow::Borrowed(string)
105    }
106}
jiff/util/borrow.rs

jiff/util/
borrow.rs
