const_panic/array_string.rs
1use crate::{
2 utils::{bytes_up_to, RangedBytes},
3 FmtArg, PanicFmt, PanicVal,
4};
5
6use core::{
7 cmp::PartialEq,
8 fmt::{self, Debug},
9};
10
11/// For precomputing a panic message.
12///
13#[cfg_attr(feature = "docsrs", doc(cfg(feature = "non_basic")))]
14#[derive(Copy, Clone)]
15pub struct ArrayString<const CAP: usize> {
16 pub(crate) len: u32,
17 pub(crate) buffer: [u8; CAP],
18}
19
20/// Equivalent of `ArrayString` which can only be up to 255 bytes long.
21///
22/// This stores the length as a `u8`, while `ArrayString` stores it as a `u32`,
23/// making this 3 bytes smaller and 1-aligned (while ArrayString is aligned to a `u32`).
24#[derive(Copy, Clone)]
25pub(crate) struct TinyString<const CAP: usize> {
26 len: u8,
27 buffer: [u8; CAP],
28}
29
30const fn add_up_lengths(mut strings: &[&str]) -> usize {
31 let mut len = 0;
32 while let [x, rem @ ..] = strings {
33 len += x.len();
34 strings = rem;
35 }
36 len
37}
38
39impl<const CAP: usize> ArrayString<CAP> {
40 /// Constructs an `ArrayString` from a `&str`
41 ///
42 /// # Panics
43 ///
44 /// Panics if `string` is larger than `CAP`.
45 ///
46 /// # Example
47 ///
48 /// ```rust
49 /// use const_panic::ArrayString;
50 ///
51 /// assert_eq!(ArrayString::<16>::new("Hello, world!"), "Hello, world!");
52 /// ```
53 pub const fn new(string: &str) -> Self {
54 Self::concat(&[string])
55 }
56
57 /// Constructs an `ArrayString` by concatenating zero or more `&str`s
58 ///
59 /// # Panics
60 ///
61 /// Panics if the concatenated string would be longer than `CAP`.
62 ///
63 /// # Example
64 ///
65 /// ```rust
66 /// use const_panic::ArrayString;
67 ///
68 /// assert_eq!(
69 /// ArrayString::<99>::concat(&["This ", "is ", "a string"]),
70 /// "This is a string"
71 /// );
72 /// ```
73 pub const fn concat(strings: &[&str]) -> Self {
74 let mut len = 0u32;
75 let mut buffer = [0u8; CAP];
76
77 let mut mstrings = strings;
78 while let [string, ref rem @ ..] = *mstrings {
79 mstrings = rem;
80 let mut bytes = string.as_bytes();
81 while let [x, ref rem @ ..] = *bytes {
82 if len == u32::MAX || len as usize >= CAP {
83 crate::concat_panic(&[&[
84 PanicVal::write_str("The input strings were longer than "),
85 PanicVal::from_usize(CAP, FmtArg::DISPLAY),
86 PanicVal::write_str(", concatenated length: "),
87 PanicVal::from_usize(add_up_lengths(strings), FmtArg::DISPLAY),
88 PanicVal::write_str(", strings: "),
89 PanicVal::from_slice_str(strings, FmtArg::DEBUG),
90 ]])
91 }
92
93 bytes = rem;
94 buffer[len as usize] = x;
95 len += 1;
96 }
97 }
98
99 Self { len, buffer }
100 }
101
102 /// Constructs this string from a `&[&[PanicVal<'_>]]`.
103 ///
104 /// Returns `None` if the formatted args would be larger than `CAP`.
105 ///
106 /// # Example
107 ///
108 /// ```rust
109 /// use const_panic::{ArrayString, FmtArg, flatten_panicvals};
110 ///
111 /// assert_eq!(
112 /// ArrayString::<17>::concat_panicvals(&[
113 /// &flatten_panicvals!(FmtArg::DEBUG; 1u8, ("hello")),
114 /// &flatten_panicvals!(FmtArg::DEBUG; &[3u8, 5, 8]),
115 /// ]).unwrap(),
116 /// "1\"hello\"[3, 5, 8]",
117 /// );
118 ///
119 /// assert!(
120 /// ArrayString::<16>::concat_panicvals(&[
121 /// &flatten_panicvals!(FmtArg::DEBUG; 1u8, ("hello")),
122 /// &flatten_panicvals!(FmtArg::DEBUG; &[3u8, 5, 8]),
123 /// ]).is_none(),
124 /// );
125 ///
126 /// ```
127 ///
128 pub const fn concat_panicvals(args: &[&[PanicVal<'_>]]) -> Option<Self> {
129 match crate::concat_panic_::make_panic_string::<CAP>(args) {
130 Ok(x) => Some(x),
131 Err(_) => None,
132 }
133 }
134
135 /// Constructs this string from a `&[PanicVal<'_>]`.
136 ///
137 /// Returns `None` if the formatted args would be larger than `CAP`.
138 ///
139 /// # Example
140 ///
141 /// ```rust
142 /// use const_panic::{ArrayString, FmtArg, flatten_panicvals};
143 ///
144 /// assert_eq!(
145 /// ArrayString::<8>::from_panicvals(
146 /// &flatten_panicvals!(FmtArg::DEBUG; 100u8, "hello")
147 /// ).unwrap(),
148 /// "100hello",
149 /// );
150 ///
151 /// // trying to format panicvals into too small an ArrayString
152 /// assert!(
153 /// ArrayString::<7>::from_panicvals(
154 /// &flatten_panicvals!(FmtArg::DEBUG; 100u8, "hello")
155 /// ).is_none(),
156 /// );
157 ///
158 /// ```
159 pub const fn from_panicvals(args: &[PanicVal<'_>]) -> Option<Self> {
160 Self::concat_panicvals(&[args])
161 }
162
163 /// How long the string is in bytes.
164 ///
165 /// # Example
166 ///
167 /// ```rust
168 /// use const_panic::ArrayString;
169 ///
170 /// assert_eq!(ArrayString::<16>::new("foo").len(), 3);
171 /// assert_eq!(ArrayString::<16>::new("foo bar").len(), 7);
172 /// assert_eq!(ArrayString::<16>::new("Hello, world!").len(), 13);
173 /// ```
174 pub const fn len(&self) -> usize {
175 self.len as usize
176 }
177
178 /// Accesses the string as a byte slice.
179 ///
180 /// # Performance
181 ///
182 /// When the "rust_1_64" feature is disabled,
183 /// this takes a linear amount of time to run, proportional to `CAP - self.len()`.
184 ///
185 /// When the "rust_1_64" feature is enabled,
186 /// this takes a constant amount of time to run.
187 ///
188 /// # Example
189 ///
190 /// ```rust
191 /// use const_panic::ArrayString;
192 ///
193 /// assert_eq!(ArrayString::<16>::new("foo").as_bytes(), b"foo");
194 /// assert_eq!(ArrayString::<16>::new("foo bar").as_bytes(), b"foo bar");
195 /// assert_eq!(ArrayString::<16>::new("Hello, world!").as_bytes(), b"Hello, world!");
196 /// ```
197 pub const fn as_bytes(&self) -> &[u8] {
198 bytes_up_to(&self.buffer, self.len())
199 }
200
201 /// Gets the string.
202 ///
203 /// # Performance
204 ///
205 /// This takes a linear amount of time to run.
206 ///
207 /// # Example
208 ///
209 /// ```rust
210 /// use const_panic::ArrayString;
211 ///
212 /// assert_eq!(ArrayString::<16>::new("foo").to_str(), "foo");
213 /// assert_eq!(ArrayString::<16>::new("foo bar").to_str(), "foo bar");
214 /// assert_eq!(ArrayString::<16>::new("Hello, world!").to_str(), "Hello, world!");
215 /// ```
216 pub const fn to_str(&self) -> &str {
217 #[cfg(not(feature = "rust_1_64"))]
218 {
219 // safety: make_panic_string delegates formatting to the `write_to_buffer` macro,
220 // which is tested as producing valid utf8.
221 unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
222 }
223
224 #[cfg(feature = "rust_1_64")]
225 match core::str::from_utf8(self.as_bytes()) {
226 Ok(x) => x,
227 Err(_) => panic!("INTERNAL BUG: the string isn't valid utf-8"),
228 }
229 }
230
231 /// Creates a single element `PanicVal` borrowing from this string.
232 pub const fn to_panicvals(&self, f: FmtArg) -> [PanicVal<'_>; 1] {
233 [PanicVal::from_str(self.to_str(), f)]
234 }
235
236 /// Creates a `PanicVal` borrowing from this string.
237 pub const fn to_panicval(&self, f: FmtArg) -> PanicVal<'_> {
238 PanicVal::from_str(self.to_str(), f)
239 }
240}
241
242impl<const CAP: usize> ArrayString<CAP> {
243 pub(crate) const fn to_compact(self) -> TinyString<CAP> {
244 if self.len() <= 255 {
245 TinyString {
246 len: self.len as u8,
247 buffer: self.buffer,
248 }
249 } else {
250 crate::concat_panic(&[&[
251 PanicVal::write_str(
252 "The input string is too long, expected `length <= 255`, found length: ",
253 ),
254 PanicVal::from_usize(self.len(), FmtArg::DISPLAY),
255 ]])
256 }
257 }
258}
259
260impl<const CAP: usize> Debug for ArrayString<CAP> {
261 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
262 Debug::fmt(self.to_str(), f)
263 }
264}
265
266impl<const CAP: usize> PartialEq<str> for ArrayString<CAP> {
267 fn eq(&self, str: &str) -> bool {
268 self.to_str() == str
269 }
270}
271impl<const CAP: usize> PartialEq<&str> for ArrayString<CAP> {
272 fn eq(&self, str: &&str) -> bool {
273 self == *str
274 }
275}
276
277impl<const CAP: usize> PanicFmt for ArrayString<CAP> {
278 type This = Self;
279 type Kind = crate::fmt::IsCustomType;
280 const PV_COUNT: usize = 1;
281}
282
283////////////////////////////////////////////////////////////////////////////////
284
285impl<const CAP: usize> TinyString<CAP> {
286 pub(crate) const fn ranged(&self) -> RangedBytes<&[u8]> {
287 RangedBytes {
288 start: 0,
289 end: self.len as usize,
290 bytes: &self.buffer,
291 }
292 }
293}