├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md └── src └── lib.rs /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "splitmut" 3 | version = "0.2.0" 4 | authors = ["David Henningsson "] 5 | license = "Apache-2.0/MIT" 6 | description = "Safely retrieves multiple mutable values from the same collection." 7 | keywords = ["mutable", "reference", "mut", "ref", "split"] 8 | documentation = "http://docs.rs/splitmut/" 9 | repository = "https://github.com/diwic/splitmut-rs" 10 | 11 | [dependencies] 12 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 19 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 20 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 21 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 22 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 23 | DEALINGS IN THE SOFTWARE. 24 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # SplitMut 2 | 3 | A Rust library for safely retrieving multiple mutable values within the same collection. 4 | 5 | [API Documentation](http://diwic.github.io/rs-docs/splitmut/index.html) 6 | [Crates.io](http://crates.io/crates/splitmut) 7 | 8 | `get2_mut`, `get3_mut` and `get4_mut` return a tuple or 2, 3 or 4 values, each one of them being 9 | one of: 10 | 11 | * `Ok(&mut V)` 12 | * `Err(SplitMutError::NoValue)` in case there was no value for the key (i e, when your usual `get_mut` would have returned `None`) 13 | * `Err(SplitMutError::SameValue)` in case the same value has already been returned earlier in the tuple. 14 | 15 | Add `use splitmut::SplitMut` to your code have these functions implemented for mutable slices, Vec, VecDeque, HashMap and BTreeMap. 16 | 17 | # Example 18 | 19 | ```rust 20 | extern crate splitmut; 21 | 22 | use std::collections::HashMap; 23 | use splitmut::{SplitMut, SplitMutError}; 24 | 25 | // Create a hashmap 26 | let mut h = HashMap::new(); 27 | h.insert(1, "Hello"); 28 | h.insert(2, "world"); 29 | 30 | // Swap two values easily 31 | { 32 | let (m1, m2) = h.get2_mut(&1, &2); 33 | std::mem::swap(m1.unwrap(), m2.unwrap()); 34 | } 35 | assert_eq!(h.get(&1), Some(&"world")); 36 | assert_eq!(h.get(&2), Some(&"Hello")); 37 | 38 | // Show error handling 39 | let (m0, m1a, m1b) = h.get3_mut(&0, &1, &1); 40 | // No value for the key "0" 41 | assert_eq!(m0, Err(SplitMutError::NoValue)); 42 | // First value for the key "1" is returned successfully 43 | assert_eq!(m1a, Ok(&mut "world")); 44 | // Second value for the key "1" returns an error 45 | assert_eq!(m1b, Err(SplitMutError::SameValue)); 46 | ``` 47 | 48 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | //! SplitMut - a crate for safely retrieving multiple mutable values within the same collection. 2 | //! 3 | //! `get2_mut`, `get3_mut` and `get4_mut` return a tuple or 2, 3 or 4 values, each one of them being 4 | //! one of `Ok(&mut V)`, `Err(SplitMutError::NoValue)` in case there was no value for the key (i e, when 5 | //! your usual `get_mut` would have returned `None`), or `Err(SplitMutError::SameValue)` in case the same 6 | //! value has already been returned earlier in the tuple. 7 | //! 8 | //! If you need more than four values, you can use `get_muts` or `get_mut_iter` to get as many mutable 9 | //! values as you like. 10 | //! 11 | //! # Example 12 | //! ``` 13 | //! use std::collections::HashMap; 14 | //! use splitmut::{SplitMut, SplitMutError}; 15 | //! 16 | //! // Create a hashmap 17 | //! let mut h = HashMap::new(); 18 | //! h.insert(1, "Hello"); 19 | //! h.insert(2, "world"); 20 | //! 21 | //! // Swap two values easily 22 | //! { 23 | //! let (m1, m2) = h.get2_mut(&1, &2); 24 | //! std::mem::swap(m1.unwrap(), m2.unwrap()); 25 | //! } 26 | //! assert_eq!(h.get(&1), Some(&"world")); 27 | //! assert_eq!(h.get(&2), Some(&"Hello")); 28 | //! 29 | //! // Show error handling 30 | //! let (m0, m1a, m1b) = h.get3_mut(&0, &1, &1); 31 | //! // No value for the key "0" 32 | //! assert_eq!(m0, Err(SplitMutError::NoValue)); 33 | //! // First value for the key "1" is returned successfully 34 | //! assert_eq!(m1a, Ok(&mut "world")); 35 | //! // Second value for the key "1" returns an error 36 | //! assert_eq!(m1b, Err(SplitMutError::SameValue)); 37 | //! ``` 38 | //! 39 | 40 | #![warn(missing_docs)] 41 | 42 | use std::collections::{HashMap, BTreeMap, HashSet, VecDeque}; 43 | use std::marker::PhantomData; 44 | use std::{hash, borrow}; 45 | 46 | /// Error returned from get*_mut functions. 47 | #[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Copy, Debug)] 48 | pub enum SplitMutError { 49 | /// No value was found for the specified key (like when get_mut would return None) 50 | NoValue, 51 | /// The same value has already been returned (earlier in the same tuple) 52 | SameValue, 53 | } 54 | 55 | impl std::error::Error for SplitMutError { 56 | fn description(&self) -> &'static str { 57 | match self { 58 | &SplitMutError::NoValue => "No value", 59 | &SplitMutError::SameValue => "Duplicate values", 60 | } 61 | } 62 | } 63 | 64 | impl std::fmt::Display for SplitMutError { 65 | fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { 66 | use std::error::Error; 67 | f.write_str(self.description()) 68 | } 69 | } 70 | 71 | // Used internally. 72 | type R = Result<*mut V, SplitMutError>; 73 | 74 | #[inline] 75 | fn to_r(s: Option<&mut V>) -> R { 76 | s.map(|s| s as *mut V).ok_or(SplitMutError::NoValue) 77 | } 78 | 79 | #[inline] 80 | fn check_r(a: &R, b: R) -> R { 81 | match (a, &b) { 82 | (&Ok(ref aa), &Ok(ref bb)) => if aa == bb { return Err(SplitMutError::SameValue) }, 83 | _ => {}, 84 | } 85 | b 86 | } 87 | 88 | #[inline] 89 | unsafe fn from_r<'a, V>(a: R) -> Result<&'a mut V, SplitMutError> { a.map(|aa| &mut *aa) } 90 | 91 | 92 | /// Just add `use splitmut::SplitMut;` to have these methods working on 93 | /// mutable slices, Vec, VecDeque, HashMap and BTreeMap. 94 | /// 95 | /// In case you want to implement `SplitMut` for your own collection, just 96 | /// implement `get1_mut` and `get1_unchecked_mut` and the other methods will 97 | /// be provided for you. If you do so, you must make sure that these functions 98 | /// do not mutate your collection in ways that would invalidate previously returned 99 | /// values from `get1_mut` and `get1_unchecked_mut`. 100 | pub unsafe trait SplitMut { 101 | /// Wrapper for get_mut, used internally. 102 | fn get1_mut(&mut self, k1: K) -> Option<&mut V>; 103 | /// Wrapper for get_unchecked_mut, used internally. 104 | /// 105 | /// # Undefined behaviour 106 | /// It is undefined behaviour to call this with a key that does not correspond to a value. 107 | /// You have been warned. 108 | unsafe fn get1_unchecked_mut(&mut self, k1: K) -> &mut V; 109 | 110 | /// Returns two mutable references to two distinct values within 111 | /// the same collection. 112 | fn get2_mut(&mut self, k1: K, k2: K) -> (Result<&mut V, SplitMutError>, Result<&mut V, SplitMutError>) { 113 | let p1 = to_r(self.get1_mut(k1)); 114 | let p2 = to_r(self.get1_mut(k2)); 115 | let p2 = check_r(&p1, p2); 116 | unsafe { (from_r(p1), from_r(p2)) } 117 | } 118 | 119 | /// Returns three mutable references to three distinct values within 120 | /// the same collection. 121 | fn get3_mut(&mut self, k1: K, k2: K, k3: K) -> (Result<&mut V, SplitMutError>, 122 | Result<&mut V, SplitMutError>, Result<&mut V, SplitMutError>) { 123 | 124 | let p1 = to_r(self.get1_mut(k1)); 125 | let p2 = to_r(self.get1_mut(k2)); 126 | let p3 = to_r(self.get1_mut(k3)); 127 | let p2 = check_r(&p1, p2); 128 | let p3 = check_r(&p1, p3); 129 | let p3 = check_r(&p2, p3); 130 | unsafe { (from_r(p1), from_r(p2), from_r(p3)) } 131 | } 132 | 133 | /// Returns four mutable references to four distinct values within 134 | /// the same collection. 135 | fn get4_mut(&mut self, k1: K, k2: K, k3: K, k4: K) -> (Result<&mut V, SplitMutError>, 136 | Result<&mut V, SplitMutError>, Result<&mut V, SplitMutError>, Result<&mut V, SplitMutError>) { 137 | let p1 = to_r(self.get1_mut(k1)); 138 | let p2 = to_r(self.get1_mut(k2)); 139 | let p3 = to_r(self.get1_mut(k3)); 140 | let p4 = to_r(self.get1_mut(k4)); 141 | let p2 = check_r(&p1, p2); 142 | let p3 = check_r(&p1, p3); 143 | let p3 = check_r(&p2, p3); 144 | let p4 = check_r(&p1, p4); 145 | let p4 = check_r(&p2, p4); 146 | let p4 = check_r(&p3, p4); 147 | unsafe { (from_r(p1), from_r(p2), from_r(p3), from_r(p4)) } 148 | } 149 | 150 | /// Returns any number mutable references to distinct values within 151 | /// the same collection. A HashSet is used internally to keep track 152 | /// of values already returned. 153 | /// 154 | /// # Example 155 | /// ``` 156 | /// use splitmut::SplitMut; 157 | /// 158 | /// let mut h = vec!["Hello", "world", "!"]; 159 | /// let mut z = h.get_muts(); 160 | /// let a = z.at(0); 161 | /// let b = z.at(1); 162 | /// assert_eq!(a, Ok(&mut "Hello")); 163 | /// assert_eq!(b, Ok(&mut "world")); 164 | /// ``` 165 | fn get_muts(&mut self) -> GetMuts { GetMuts(self, HashSet::new(), PhantomData) } 166 | 167 | /// Returns an iterator adapter that maps from a K to a Result. 168 | /// A HashSet is used internally to keep track of values already returned. 169 | /// 170 | /// # Example 171 | /// ``` 172 | /// use std::collections::BTreeMap; 173 | /// use splitmut::{SplitMut, SplitMutError}; 174 | /// 175 | /// let mut h = BTreeMap::new(); 176 | /// h.insert(String::from("borrow"), 1); 177 | /// h.insert(String::from("me"), 2); 178 | /// let slice = ["me", "borrow", "me"]; 179 | /// let z: Vec<_> = h.get_mut_iter(slice.into_iter().map(|&k| k)).collect(); 180 | /// assert_eq!(&*z, [Ok(&mut 2), Ok(&mut 1), Err(SplitMutError::SameValue)]); 181 | /// ``` 182 | fn get_mut_iter>(&mut self, i: I) -> GetMutIter { GetMutIter(self.get_muts(), i) } 183 | 184 | /// Returns two mutable references to two distinct values within 185 | /// the same collection. 186 | /// 187 | /// # Undefined behaviour 188 | /// It is undefined behaviour to call this with a key that does not 189 | /// correspond to a value, or with keys pointing to the same value. 190 | /// You have been warned. 191 | unsafe fn get2_unchecked_mut(&mut self, k1: K, k2: K) -> (&mut V, &mut V) { 192 | let p2 = self.get1_unchecked_mut(k2) as *mut V; 193 | (self.get1_unchecked_mut(k1), &mut *p2) 194 | } 195 | 196 | /// Returns three mutable references to three distinct values within 197 | /// the same collection. 198 | /// 199 | /// # Undefined behaviour 200 | /// It is undefined behaviour to call this with a key that does not 201 | /// correspond to a value, or with any two keys pointing to the same value. 202 | /// You have been warned. 203 | unsafe fn get3_unchecked_mut(&mut self, k1: K, k2: K, k3: K) -> (&mut V, &mut V, &mut V) { 204 | let p2 = self.get1_unchecked_mut(k2) as *mut V; 205 | let p3 = self.get1_unchecked_mut(k3) as *mut V; 206 | (self.get1_unchecked_mut(k1), &mut *p2, &mut *p3) 207 | } 208 | 209 | /// Returns four mutable references to four distinct values within 210 | /// the same collection. 211 | /// 212 | /// # Undefined behaviour 213 | /// It is undefined behaviour to call this with a key that does not 214 | /// correspond to a value, or with any two keys pointing to the same value. 215 | /// You have been warned. 216 | unsafe fn get4_unchecked_mut(&mut self, k1: K, k2: K, k3: K, k4: K) -> (&mut V, &mut V, &mut V, &mut V) { 217 | let p2 = self.get1_unchecked_mut(k2) as *mut V; 218 | let p3 = self.get1_unchecked_mut(k3) as *mut V; 219 | let p4 = self.get1_unchecked_mut(k4) as *mut V; 220 | (self.get1_unchecked_mut(k1), &mut *p2, &mut *p3, &mut *p4) 221 | } 222 | } 223 | 224 | /// Wrapper struct for the get_muts function. 225 | pub struct GetMuts<'a, K, V, A: 'a + SplitMut + ?Sized>(&'a mut A, HashSet<*mut V>, PhantomData<*const K>); 226 | 227 | impl<'a, K, V, A: 'a + SplitMut + ?Sized> GetMuts<'a, K, V, A> { 228 | /// Returns a mutable reference with the same lifetime as the 229 | /// original collection, i e, it allows several distinct mutable references to 230 | /// be alive simultaneously. 231 | /// 232 | /// It returnes an error if the value does not exist or has already been returned. 233 | pub fn at(&mut self, k: K) -> Result<&'a mut V, SplitMutError> { 234 | let p = try!(to_r(self.0.get1_mut(k))); 235 | if !self.1.insert(p) { return Err(SplitMutError::SameValue) }; 236 | Ok(unsafe { &mut *p }) 237 | } 238 | } 239 | 240 | 241 | /// Wrapper struct for the get_mut_iter function. 242 | pub struct GetMutIter<'a, K, V, A: 'a + SplitMut + ?Sized, I>(GetMuts<'a, K, V, A>, I); 243 | 244 | impl<'a, K, V: 'a, A: 'a + SplitMut + ?Sized, I: Iterator> Iterator for GetMutIter<'a, K, V, A, I> { 245 | type Item = Result<&'a mut V, SplitMutError>; 246 | fn next(&mut self) -> Option { 247 | self.1.next().map(|k| self.0.at(k)) 248 | } 249 | } 250 | 251 | 252 | unsafe impl<'a, V> SplitMut for &'a mut [V] { 253 | #[inline] 254 | fn get1_mut(&mut self, k: usize) -> Option<&mut V> { self.get_mut(k) } 255 | #[inline] 256 | unsafe fn get1_unchecked_mut(&mut self, k: usize) -> &mut V { self.get_unchecked_mut(k) } 257 | } 258 | 259 | unsafe impl<'a, V> SplitMut for Vec { 260 | #[inline] 261 | fn get1_mut(&mut self, k: usize) -> Option<&mut V> { self.get_mut(k) } 262 | #[inline] 263 | unsafe fn get1_unchecked_mut(&mut self, k: usize) -> &mut V { self.get_unchecked_mut(k) } 264 | } 265 | 266 | unsafe impl<'a, V> SplitMut for VecDeque { 267 | #[inline] 268 | fn get1_mut(&mut self, k: usize) -> Option<&mut V> { self.get_mut(k) } 269 | #[inline] 270 | unsafe fn get1_unchecked_mut(&mut self, k: usize) -> &mut V { std::mem::transmute(self.get_mut(k)) } 271 | } 272 | 273 | unsafe impl<'a, K: hash::Hash + Eq + borrow::Borrow, Q: hash::Hash + Eq + ?Sized, V, S: hash::BuildHasher> SplitMut<&'a Q, V> for HashMap { 274 | #[inline] 275 | fn get1_mut(&mut self, k: &'a Q) -> Option<&mut V> { self.get_mut(k) } 276 | #[inline] 277 | unsafe fn get1_unchecked_mut(&mut self, k: &'a Q) -> &mut V { std::mem::transmute(self.get_mut(k)) } 278 | } 279 | 280 | unsafe impl<'a, K: Ord + borrow::Borrow, Q: Ord + ?Sized, V> SplitMut<&'a Q, V> for BTreeMap { 281 | #[inline] 282 | fn get1_mut(&mut self, k: &'a Q) -> Option<&mut V> { self.get_mut(k) } 283 | #[inline] 284 | unsafe fn get1_unchecked_mut(&mut self, k: &'a Q) -> &mut V { std::mem::transmute(self.get_mut(k)) } 285 | } 286 | 287 | #[test] 288 | fn hash_same() { 289 | let mut h = HashMap::new(); 290 | h.insert(3u8, 5u16); 291 | assert_eq!(h.get2_mut(&3, &3), (Ok(&mut 5u16), Err(SplitMutError::SameValue))); 292 | } 293 | 294 | #[test] 295 | fn hash_reg() { 296 | let mut h = HashMap::new(); 297 | h.insert(3u8, 5u16); 298 | h.insert(4u8, 9u16); 299 | { let (a, b) = h.get2_mut(&3, &4); 300 | std::mem::swap(a.unwrap(), b.unwrap()); 301 | } 302 | assert_eq!(h.get2_mut(&2, &2), (Err(SplitMutError::NoValue), Err(SplitMutError::NoValue))); 303 | assert_eq!(unsafe { h.get2_unchecked_mut(&3, &4) }, (&mut 9u16, &mut 5u16)); 304 | assert_eq!(h.get2_mut(&2, &3), (Err(SplitMutError::NoValue), Ok(&mut 9u16))); 305 | } 306 | 307 | #[test] 308 | fn tree_borrow() { 309 | let mut h = BTreeMap::new(); 310 | h.insert(String::from("borrow"), 1); 311 | h.insert(String::from("me"), 2); 312 | let slice = ["me", "borrow", "me"]; 313 | let z: Vec<_> = h.get_mut_iter(slice.into_iter().map(|&k| k)).collect(); 314 | assert_eq!(&*z, [Ok(&mut 2), Ok(&mut 1), Err(SplitMutError::SameValue)]); 315 | } 316 | 317 | #[test] 318 | fn deque_same() { 319 | let mut h = VecDeque::new(); 320 | h.push_front(5u16); 321 | assert_eq!(h.get2_mut(0, 0), (Ok(&mut 5u16), Err(SplitMutError::SameValue))); 322 | } 323 | 324 | #[test] 325 | fn deque_reg() { 326 | let mut h = VecDeque::new(); 327 | h.push_back(5u16); 328 | h.push_back(9u16); 329 | { let (a, b) = h.get2_mut(0, 1); 330 | std::mem::swap(a.unwrap(), b.unwrap()); 331 | } 332 | assert_eq!(h.get2_mut(2, 2), (Err(SplitMutError::NoValue), Err(SplitMutError::NoValue))); 333 | assert_eq!(unsafe { h.get2_unchecked_mut(0, 1) }, (&mut 9u16, &mut 5u16)); 334 | assert_eq!(h.get2_mut(2, 0), (Err(SplitMutError::NoValue), Ok(&mut 9u16))); 335 | } 336 | 337 | #[test] 338 | fn vec() { 339 | let mut h = vec!["Hello", "world", "!"]; 340 | { let (a, b, c) = h.get3_mut(0, 1, 2); 341 | *c.unwrap() = "universe"; 342 | std::mem::swap(a.unwrap(), b.unwrap()); 343 | } 344 | assert_eq!(&*h, &["world", "Hello", "universe"]); 345 | 346 | { 347 | let mut z = h.get_muts(); 348 | let a = z.at(0); 349 | let b = z.at(1); 350 | assert_eq!(a, Ok(&mut "world")); 351 | assert_eq!(b, Ok(&mut "Hello")); 352 | std::mem::swap(a.unwrap(), b.unwrap()); 353 | assert_eq!(z.at(0), Err(SplitMutError::SameValue)); 354 | assert_eq!(z.at(3), Err(SplitMutError::NoValue)); 355 | } 356 | assert_eq!(&*h, &["Hello", "world", "universe"]); 357 | } 358 | --------------------------------------------------------------------------------