/rust/registry/src/index.crates.io-1949cf8c6b5b557f/memchr-2.8.0/src/cow.rs
Line | Count | Source |
1 | | use core::ops; |
2 | | |
3 | | /// A specialized copy-on-write byte string. |
4 | | /// |
5 | | /// The purpose of this type is to permit usage of a "borrowed or owned |
6 | | /// byte string" in a way that keeps std/no-std compatibility. That is, in |
7 | | /// no-std/alloc mode, this type devolves into a simple &[u8] with no owned |
8 | | /// variant available. We can't just use a plain Cow because Cow is not in |
9 | | /// core. |
10 | | #[derive(Clone, Debug)] |
11 | | pub struct CowBytes<'a>(Imp<'a>); |
12 | | |
13 | | // N.B. We don't use alloc::borrow::Cow here since we can get away with a |
14 | | // Box<[u8]> for our use case, which is 1/3 smaller than the Vec<u8> that |
15 | | // a Cow<[u8]> would use. |
16 | | #[cfg(feature = "alloc")] |
17 | | #[derive(Clone, Debug)] |
18 | | enum Imp<'a> { |
19 | | Borrowed(&'a [u8]), |
20 | | Owned(alloc::boxed::Box<[u8]>), |
21 | | } |
22 | | |
23 | | #[cfg(not(feature = "alloc"))] |
24 | | #[derive(Clone, Debug)] |
25 | | struct Imp<'a>(&'a [u8]); |
26 | | |
27 | | impl<'a> ops::Deref for CowBytes<'a> { |
28 | | type Target = [u8]; |
29 | | |
30 | | #[inline(always)] |
31 | 0 | fn deref(&self) -> &[u8] { |
32 | 0 | self.as_slice() |
33 | 0 | } |
34 | | } |
35 | | |
36 | | impl<'a> CowBytes<'a> { |
37 | | /// Create a new borrowed CowBytes. |
38 | | #[inline(always)] |
39 | 0 | pub(crate) fn new<B: ?Sized + AsRef<[u8]>>(bytes: &'a B) -> CowBytes<'a> { |
40 | 0 | CowBytes(Imp::new(bytes.as_ref())) |
41 | 0 | } |
42 | | |
43 | | /// Create a new owned CowBytes. |
44 | | #[cfg(feature = "alloc")] |
45 | | #[inline(always)] |
46 | 0 | pub(crate) fn new_owned( |
47 | 0 | bytes: alloc::boxed::Box<[u8]>, |
48 | 0 | ) -> CowBytes<'static> { |
49 | 0 | CowBytes(Imp::Owned(bytes)) |
50 | 0 | } |
51 | | |
52 | | /// Return a borrowed byte string, regardless of whether this is an owned |
53 | | /// or borrowed byte string internally. |
54 | | #[inline(always)] |
55 | 0 | pub(crate) fn as_slice(&self) -> &[u8] { |
56 | 0 | self.0.as_slice() |
57 | 0 | } |
58 | | |
59 | | /// Return an owned version of this copy-on-write byte string. |
60 | | /// |
61 | | /// If this is already an owned byte string internally, then this is a |
62 | | /// no-op. Otherwise, the internal byte string is copied. |
63 | | #[cfg(feature = "alloc")] |
64 | | #[inline(always)] |
65 | 0 | pub(crate) fn into_owned(self) -> CowBytes<'static> { |
66 | 0 | match self.0 { |
67 | 0 | Imp::Borrowed(b) => { |
68 | 0 | CowBytes::new_owned(alloc::boxed::Box::from(b)) |
69 | | } |
70 | 0 | Imp::Owned(b) => CowBytes::new_owned(b), |
71 | | } |
72 | 0 | } |
73 | | } |
74 | | |
75 | | impl<'a> Imp<'a> { |
76 | | #[inline(always)] |
77 | 0 | pub fn new(bytes: &'a [u8]) -> Imp<'a> { |
78 | | #[cfg(feature = "alloc")] |
79 | | { |
80 | 0 | Imp::Borrowed(bytes) |
81 | | } |
82 | | #[cfg(not(feature = "alloc"))] |
83 | | { |
84 | | Imp(bytes) |
85 | | } |
86 | 0 | } |
87 | | |
88 | | #[cfg(feature = "alloc")] |
89 | | #[inline(always)] |
90 | 0 | pub fn as_slice(&self) -> &[u8] { |
91 | | #[cfg(feature = "alloc")] |
92 | | { |
93 | 0 | match self { |
94 | 0 | Imp::Owned(ref x) => x, |
95 | 0 | Imp::Borrowed(x) => x, |
96 | | } |
97 | | } |
98 | | #[cfg(not(feature = "alloc"))] |
99 | | { |
100 | | self.0 |
101 | | } |
102 | 0 | } |
103 | | |
104 | | #[cfg(not(feature = "alloc"))] |
105 | | #[inline(always)] |
106 | | pub fn as_slice(&self) -> &[u8] { |
107 | | self.0 |
108 | | } |
109 | | } |