/rust/registry/src/index.crates.io-1949cf8c6b5b557f/memchr-2.5.0/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 mode, this type devolves into a simple &[u8] with no owned variant |
8 | | /// available. We can't just use a plain Cow because Cow is not in core. |
9 | | #[derive(Clone, Debug)] |
10 | | pub struct CowBytes<'a>(Imp<'a>); |
11 | | |
12 | | // N.B. We don't use std::borrow::Cow here since we can get away with a |
13 | | // Box<[u8]> for our use case, which is 1/3 smaller than the Vec<u8> that |
14 | | // a Cow<[u8]> would use. |
15 | | #[cfg(feature = "std")] |
16 | | #[derive(Clone, Debug)] |
17 | | enum Imp<'a> { |
18 | | Borrowed(&'a [u8]), |
19 | | Owned(Box<[u8]>), |
20 | | } |
21 | | |
22 | | #[cfg(not(feature = "std"))] |
23 | | #[derive(Clone, Debug)] |
24 | | struct Imp<'a>(&'a [u8]); |
25 | | |
26 | | impl<'a> ops::Deref for CowBytes<'a> { |
27 | | type Target = [u8]; |
28 | | |
29 | | #[inline(always)] |
30 | 0 | fn deref(&self) -> &[u8] { |
31 | 0 | self.as_slice() |
32 | 0 | } |
33 | | } |
34 | | |
35 | | impl<'a> CowBytes<'a> { |
36 | | /// Create a new borrowed CowBytes. |
37 | | #[inline(always)] |
38 | 0 | pub fn new<B: ?Sized + AsRef<[u8]>>(bytes: &'a B) -> CowBytes<'a> { |
39 | 0 | CowBytes(Imp::new(bytes.as_ref())) |
40 | 0 | } |
41 | | |
42 | | /// Create a new owned CowBytes. |
43 | | #[cfg(feature = "std")] |
44 | | #[inline(always)] |
45 | 0 | pub fn new_owned(bytes: Box<[u8]>) -> CowBytes<'static> { |
46 | 0 | CowBytes(Imp::Owned(bytes)) |
47 | 0 | } |
48 | | |
49 | | /// Return a borrowed byte string, regardless of whether this is an owned |
50 | | /// or borrowed byte string internally. |
51 | | #[inline(always)] |
52 | 0 | pub fn as_slice(&self) -> &[u8] { |
53 | 0 | self.0.as_slice() |
54 | 0 | } |
55 | | |
56 | | /// Return an owned version of this copy-on-write byte string. |
57 | | /// |
58 | | /// If this is already an owned byte string internally, then this is a |
59 | | /// no-op. Otherwise, the internal byte string is copied. |
60 | | #[cfg(feature = "std")] |
61 | | #[inline(always)] |
62 | 0 | pub fn into_owned(self) -> CowBytes<'static> { |
63 | 0 | match self.0 { |
64 | 0 | Imp::Borrowed(b) => CowBytes::new_owned(Box::from(b)), |
65 | 0 | Imp::Owned(b) => CowBytes::new_owned(b), |
66 | | } |
67 | 0 | } |
68 | | } |
69 | | |
70 | | impl<'a> Imp<'a> { |
71 | | #[cfg(feature = "std")] |
72 | | #[inline(always)] |
73 | 0 | pub fn new(bytes: &'a [u8]) -> Imp<'a> { |
74 | 0 | Imp::Borrowed(bytes) |
75 | 0 | } |
76 | | |
77 | | #[cfg(not(feature = "std"))] |
78 | | #[inline(always)] |
79 | | pub fn new(bytes: &'a [u8]) -> Imp<'a> { |
80 | | Imp(bytes) |
81 | | } |
82 | | |
83 | | #[cfg(feature = "std")] |
84 | | #[inline(always)] |
85 | 0 | pub fn as_slice(&self) -> &[u8] { |
86 | 0 | match self { |
87 | 0 | Imp::Owned(ref x) => x, |
88 | 0 | Imp::Borrowed(x) => x, |
89 | | } |
90 | 0 | } |
91 | | |
92 | | #[cfg(not(feature = "std"))] |
93 | | #[inline(always)] |
94 | | pub fn as_slice(&self) -> &[u8] { |
95 | | self.0 |
96 | | } |
97 | | } |