1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425
//! A `Slab` is a pre-allocated block of memory, used during the //! parse/compile/eval phases to reduce memory allocation/deallocation. //! //! A `Slab` enables you to perform one single, large allocation at the //! beginning of the parse-compile-eval process, rather than many small //! allocations. You can also re-use a `Slab` for multiple expression //! parse-compile-eval cycles, greatly reducing the amount of memory //! operations. The `Slab` is the main key to `fasteval`'s excellent //! performance. //! //! You use `ExpressionI`, `ValueI`, and `InstructionI` index types to refer to //! elements within the `Slab`. These special index types are necessary to //! side-step the Rust borrow checker, which is not able to understand //! borrow-splitting of contiguous allocations (like arrays). //! (In other words, these special index types allows `fasteval` to mutate a //! `Slab` while simultaneously holding references to its contents.) //! //! You usually won't use any of the `Slab` method directly. Instead, you'll //! just pass a reference to other functions like [`parse()`](../parser/index.html), //! [`compile()`](../compiler/trait.Compiler.html) and [`eval()`](../evaler/trait.Evaler.html). //! We treat a `Slab` sort of like a Context in other programming systems. //! //! The `Slab` contains two fields: `ps` ("Parse Slab") and `cs` //! ("Compile Slab"). It is structured like this because of Rust's borrowing //! rules, so that the two fields can be borrowed and mutated independently. //! //! If you use the [`ez_eval()`](../ez/fn.ez_eval.html) function, it allocates //! a Slab for you. If you are performing the parse/compile/eval process //! yourself, then you'll need to allocate a Slab at the beginning. //! //! # Examples //! //! Here is an example of re-using one `Slab` for multiple parse/eval cycles: //! ``` //! use fasteval::Evaler; // import this trait so we can call eval(). //! fn main() -> Result<(), fasteval::Error> { //! let parser = fasteval::Parser::new(); //! let mut slab = fasteval::Slab::new(); //! //! let val = parser.parse("1+2*3-4", &mut slab.ps)?.from(&slab.ps).eval(&slab, &mut fasteval::EmptyNamespace)?; //! assert_eq!(val, 3.0); //! //! // Let's re-use the same slab again to save memory operations. //! //! // `parse()` will clear the Slab's data. It is important that you //! // do not use an old expression after the Slab has been cleared. //! let val = parser.parse("5+6*7-8", &mut slab.ps)?.from(&slab.ps).eval(&slab, &mut fasteval::EmptyNamespace)?; //! assert_eq!(val, 39.0); //! //! Ok(()) //! } //! ``` use crate::error::Error; use crate::parser::{ExpressionI, ValueI, Expression, Value}; use crate::compiler::{Instruction::{self, IConst}, InstructionI}; use std::fmt; use std::mem; #[cfg(feature="unsafe-vars")] use std::collections::BTreeMap; // Eliminate function call overhead: macro_rules! get_expr { ($pslab:expr, $i_ref:ident) => { match $pslab.exprs.get($i_ref.0) { Some(expr_ref) => expr_ref, None => &$pslab.def_expr, } }; } macro_rules! get_val { ($pslab:expr, $i_ref:ident) => { match $pslab.vals.get($i_ref.0) { Some(val_ref) => val_ref, None => &$pslab.def_val, } }; } // The CompileSlab::get_instr method is in the hot path of compiled evaluation: macro_rules! get_instr { ($cslab:expr, $i_ref:ident) => { match $cslab.instrs.get($i_ref.0) { Some(instr_ref) => instr_ref, None => &$cslab.def_instr, } }; } impl ExpressionI { /// Gets an Expression reference from the ParseSlab. /// /// This is actually just a convenience function built on top of /// `ParseSlab.get_expr`, but it enables you to perform the entire /// parse/compile/eval process in one line without upsetting the Rust /// borrow checker. (If you didn't have this function, the borrow checker /// would force you to split the process into at least two lines.) /// #[inline] pub fn from(self, ps:&ParseSlab) -> &Expression { get_expr!(ps,self) } } impl ValueI { /// Gets a Value reference from the ParseSlab. /// /// See the comments on [ExpressionI::from](struct.ExpressionI.html#method.from). /// #[inline] pub fn from(self, ps:&ParseSlab) -> &Value { get_val!(ps,self) } } /// [See the `slab module` documentation.](index.html) pub struct Slab { pub ps:ParseSlab, pub cs:CompileSlab, } /// `ParseSlab` is where `parse()` results are stored, located at `Slab.ps`. /// /// # Unsafe Variable Registration with `add_unsafe_var()` /// /// (This is documented here because the /// [`add_unsafe_var()`](#method.add_unsafe_var) method and its documentation /// only appears if `fasteval` is built with the `unsafe-vars` feature (`cargo /// build --features unsafe-vars`). I want this documentation to appear /// regardless of the build mode, so I'm putting it here.) /// /// Here is the function signature of the `add_unsafe_var()` method: /// /// ```text /// pub unsafe fn add_unsafe_var(&mut self, name: String, ptr: &f64) /// ``` /// /// If you are using [Unsafe Variables](../index.html#unsafe-variables), you /// need to pre-register the unsafe variable names and pointers *before* /// calling `parse()`. This is because Unsafe Variables are represented /// specially in the parse AST; therefore, `parse()` needs to know what /// variables are unsafe and which ones are normal so that it can produce the /// correct AST. /// /// If you forget to pre-register an unsafe variable before `parse()`, the /// variable will be treated like a Normal Variable, and you'll probably get an /// [`Undefined`](../error/enum.Error.html#variant.Undefined) error during evaluation. /// /// ## Safety /// /// You must guarantee that Unsafe Variable pointers remain valid for the /// lifetime of the resulting expression. If you continue to use an expression /// after the memory of an unsafe variable has been reclaimed, you will have /// undefined behavior. /// /// /// ## Examples /// /// Here is an example of correct and incorrect use of unsafe variable pointers: /// /// ``` /// use fasteval::Evaler; // use this trait so we can call eval(). /// use fasteval::Compiler; // use this trait so we can call compile(). /// /// // Here is an example of INCORRECT registration. DO NOT DO THIS! /// fn bad_unsafe_var(slab_mut:&mut fasteval::Slab) { /// let bad : f64 = 0.0; /// /// // Saves a pointer to 'bad': /// unsafe { slab_mut.ps.add_unsafe_var("bad".to_string(), &bad); } // `add_unsafe_var()` only exists if the `unsafe-vars` feature is enabled: `cargo test --features unsafe-vars` /// /// // 'bad' goes out-of-scope here, and the pointer we registered is no longer valid! /// // This will result in undefined behavior. /// } /// /// fn main() -> Result<(), fasteval::Error> { /// let mut slab = fasteval::Slab::new(); /// /// // The Unsafe Variable will use a pointer to read this memory location: /// // You must make sure that this variable stays in-scope as long as the /// // expression is in-use. /// let mut deg : f64 = 0.0; /// /// // Unsafe Variables must be registered before 'parse()'. /// // (Normal Variables only need definitions during the 'eval' phase.) /// unsafe { slab.ps.add_unsafe_var("deg".to_string(), °); } // `add_unsafe_var()` only exists if the `unsafe-vars` feature is enabled: `cargo test --features unsafe-vars` /// /// // bad_unsafe_var(&mut slab); // Don't do it this way. /// /// let expr_str = "sin(deg/360 * 2*pi())"; /// let expr_ref = fasteval::Parser::new().parse(expr_str, &mut slab.ps)?.from(&slab.ps); /// /// // The main reason people use Unsafe Variables is to maximize performance. /// // Compilation also helps performance, so it is usually used together with Unsafe Variables: /// let compiled = expr_ref.compile(&slab.ps, &mut slab.cs); /// /// let mut ns = fasteval::EmptyNamespace; // We only define unsafe variables, not normal variables, /// // so EmptyNamespace is fine. /// /// for d in 0..360 { /// deg = d as f64; /// let val = fasteval::eval_compiled!(compiled, &slab, &mut ns); /// eprintln!("sin({}°) = {}", deg, val); /// } /// /// Ok(()) /// } /// /// ``` pub struct ParseSlab { pub(crate) exprs :Vec<Expression>, pub(crate) vals :Vec<Value>, pub(crate) def_expr :Expression, pub(crate) def_val :Value, pub(crate) char_buf :String, #[cfg(feature="unsafe-vars")] pub(crate) unsafe_vars:BTreeMap<String, *const f64>, } /// `CompileSlab` is where `compile()` results are stored, located at `Slab.cs`. pub struct CompileSlab { pub(crate) instrs :Vec<Instruction>, pub(crate) def_instr:Instruction, } impl ParseSlab { /// Returns a reference to the [`Expression`](../parser/struct.Expression.html) /// located at `expr_i` within the `ParseSlab.exprs'. /// /// If `expr_i` is out-of-bounds, a reference to a default `Expression` is returned. /// #[inline] pub fn get_expr(&self, expr_i:ExpressionI) -> &Expression { // I'm using this non-panic match structure to boost performance: match self.exprs.get(expr_i.0) { Some(expr_ref) => expr_ref, None => &self.def_expr, } } /// Returns a reference to the [`Value`](../parser/enum.Value.html) /// located at `val_i` within the `ParseSlab.vals'. /// /// If `val_i` is out-of-bounds, a reference to a default `Value` is returned. /// #[inline] pub fn get_val(&self, val_i:ValueI) -> &Value { match self.vals.get(val_i.0) { Some(val_ref) => val_ref, None => &self.def_val, } } /// Appends an `Expression` to `ParseSlab.exprs`. /// /// # Errors /// /// If `ParseSlab.exprs` is already full, a `SlabOverflow` error is returned. /// #[inline] pub(crate) fn push_expr(&mut self, expr:Expression) -> Result<ExpressionI,Error> { let i = self.exprs.len(); if i>=self.exprs.capacity() { return Err(Error::SlabOverflow); } self.exprs.push(expr); Ok(ExpressionI(i)) } /// Appends a `Value` to `ParseSlab.vals`. /// /// # Errors /// /// If `ParseSlab.vals` is already full, a `SlabOverflow` error is returned. /// #[inline] pub(crate) fn push_val(&mut self, val:Value) -> Result<ValueI,Error> { let i = self.vals.len(); if i>=self.vals.capacity() { return Err(Error::SlabOverflow); } self.vals.push(val); Ok(ValueI(i)) } /// Clears all data from `ParseSlab.exprs` and `ParseSlab.vals`. #[inline] pub fn clear(&mut self) { self.exprs.clear(); self.vals.clear(); } /// [See the `add_unsafe_var()` documentation above.](#unsafe-variable-registration-with-add_unsafe_var) #[cfg(feature="unsafe-vars")] #[allow(clippy::trivially_copy_pass_by_ref)] pub unsafe fn add_unsafe_var(&mut self, name:String, ptr:&f64) { self.unsafe_vars.insert(name, ptr as *const f64); } } impl CompileSlab { /// Returns a reference to the [`Instruction`](../compiler/enum.Instruction.html) /// located at `instr_i` within the `CompileSlab.instrs'. /// /// If `instr_i` is out-of-bounds, a reference to a default `Instruction` is returned. /// #[inline] pub fn get_instr(&self, instr_i:InstructionI) -> &Instruction { match self.instrs.get(instr_i.0) { Some(instr_ref) => instr_ref, None => &self.def_instr, } } /// Appends an `Instruction` to `CompileSlab.instrs`. pub(crate) fn push_instr(&mut self, instr:Instruction) -> InstructionI { if self.instrs.capacity()==0 { self.instrs.reserve(32); } let i = self.instrs.len(); self.instrs.push(instr); InstructionI(i) } /// Removes an `Instruction` from `CompileSlab.instrs` as efficiently as possible. pub(crate) fn take_instr(&mut self, i:InstructionI) -> Instruction { if i.0==self.instrs.len()-1 { match self.instrs.pop() { Some(instr) => instr, None => IConst(std::f64::NAN), } } else { match self.instrs.get_mut(i.0) { Some(instr_ref) => mem::replace(instr_ref, IConst(std::f64::NAN)), // Replace with a conspicuous value in case we use it by accident. None => IConst(std::f64::NAN), } } } /// Clears all data from `CompileSlab.instrs`. #[inline] pub fn clear(&mut self) { self.instrs.clear(); } } impl Slab { /// Creates a new default-sized `Slab`. #[inline] pub fn new() -> Self { Self::with_capacity(64) } /// Creates a new `Slab` with the given capacity. #[inline] pub fn with_capacity(cap:usize) -> Self { Self{ ps:ParseSlab{ exprs :Vec::with_capacity(cap), vals :Vec::with_capacity(cap), def_expr :Default::default(), def_val :Default::default(), char_buf :String::with_capacity(64), #[cfg(feature="unsafe-vars")] unsafe_vars:BTreeMap::new(), }, cs:CompileSlab{ instrs :Vec::new(), // Don't pre-allocate for compilation. def_instr:Default::default(), }, } } /// Clears all data from [`Slab.ps`](struct.ParseSlab.html) and [`Slab.cs`](struct.CompileSlab.html). #[inline] pub fn clear(&mut self) { self.ps.exprs.clear(); self.ps.vals.clear(); self.cs.instrs.clear(); } } fn write_indexed_list<T>(f:&mut fmt::Formatter, lst:&[T]) -> Result<(), fmt::Error> where T:fmt::Debug { write!(f, "{{")?; let mut nonempty = false; for (i,x) in lst.iter().enumerate() { if nonempty { write!(f, ",")?; } nonempty = true; write!(f, " {}:{:?}",i,x)?; } if nonempty { write!(f, " ")?; } write!(f, "}}")?; Ok(()) } impl fmt::Debug for Slab { fn fmt(&self, f:&mut fmt::Formatter) -> Result<(), fmt::Error> { write!(f, "Slab{{ exprs:")?; write_indexed_list(f, &self.ps.exprs)?; write!(f, ", vals:")?; write_indexed_list(f, &self.ps.vals)?; write!(f, ", instrs:")?; write_indexed_list(f, &self.cs.instrs)?; write!(f, " }}")?; Ok(()) } } impl fmt::Debug for ParseSlab { fn fmt(&self, f:&mut fmt::Formatter) -> Result<(), fmt::Error> { write!(f, "ParseSlab{{ exprs:")?; write_indexed_list(f, &self.exprs)?; write!(f, ", vals:")?; write_indexed_list(f, &self.vals)?; write!(f, " }}")?; Ok(()) } } impl fmt::Debug for CompileSlab { fn fmt(&self, f:&mut fmt::Formatter) -> Result<(), fmt::Error> { write!(f, "CompileSlab{{ instrs:")?; write_indexed_list(f, &self.instrs)?; write!(f, " }}")?; Ok(()) } } impl Default for Slab { fn default() -> Self { Self::with_capacity(64) } }