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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447
use std::cmp::Ordering;
use std::collections::HashMap;
use std::fmt;
use std::mem;
use std::ops::Deref;
use std::slice;
use std::sync::Arc;
use crate::input::Char;
use crate::literal::LiteralSearcher;
/// `InstPtr` represents the index of an instruction in a regex program.
pub type InstPtr = usize;
/// Program is a sequence of instructions and various facts about thos
/// instructions.
#[derive(Clone)]
pub struct Program {
/// A sequence of instructions that represents an NFA.
pub insts: Vec<Inst>,
/// Pointers to each Match instruction in the sequence.
///
/// This is always length 1 unless this program represents a regex set.
pub matches: Vec<InstPtr>,
/// The ordered sequence of all capture groups extracted from the AST.
/// Unnamed groups are `None`.
pub captures: Vec<Option<String>>,
/// Pointers to all named capture groups into `captures`.
pub capture_name_idx: Arc<HashMap<String, usize>>,
/// A pointer to the start instruction. This can vary depending on how
/// the program was compiled. For example, programs for use with the DFA
/// engine have a `.*?` inserted at the beginning of unanchored regular
/// expressions. The actual starting point of the program is after the
/// `.*?`.
pub start: InstPtr,
/// A set of equivalence classes for discriminating bytes in the compiled
/// program.
pub byte_classes: Vec<u8>,
/// When true, this program can only match valid UTF-8.
pub only_utf8: bool,
/// When true, this program uses byte range instructions instead of Unicode
/// range instructions.
pub is_bytes: bool,
/// When true, the program is compiled for DFA matching. For example, this
/// implies `is_bytes` and also inserts a preceding `.*?` for unanchored
/// regexes.
pub is_dfa: bool,
/// When true, the program matches text in reverse (for use only in the
/// DFA).
pub is_reverse: bool,
/// Whether the regex must match from the start of the input.
pub is_anchored_start: bool,
/// Whether the regex must match at the end of the input.
pub is_anchored_end: bool,
/// Whether this program contains a Unicode word boundary instruction.
pub has_unicode_word_boundary: bool,
/// A possibly empty machine for very quickly matching prefix literals.
pub prefixes: LiteralSearcher,
/// A limit on the size of the cache that the DFA is allowed to use while
/// matching.
///
/// The cache limit specifies approximately how much space we're willing to
/// give to the state cache. Once the state cache exceeds the size, it is
/// wiped and all states must be re-computed.
///
/// Note that this value does not impact correctness. It can be set to 0
/// and the DFA will run just fine. (It will only ever store exactly one
/// state in the cache, and will likely run very slowly, but it will work.)
///
/// Also note that this limit is *per thread of execution*. That is,
/// if the same regex is used to search text across multiple threads
/// simultaneously, then the DFA cache is not shared. Instead, copies are
/// made.
pub dfa_size_limit: usize,
}
impl Program {
/// Creates an empty instruction sequence. Fields are given default
/// values.
pub fn new() -> Self {
Program {
insts: vec![],
matches: vec![],
captures: vec![],
capture_name_idx: Arc::new(HashMap::new()),
start: 0,
byte_classes: vec![0; 256],
only_utf8: true,
is_bytes: false,
is_dfa: false,
is_reverse: false,
is_anchored_start: false,
is_anchored_end: false,
has_unicode_word_boundary: false,
prefixes: LiteralSearcher::empty(),
dfa_size_limit: 2 * (1 << 20),
}
}
/// If pc is an index to a no-op instruction (like Save), then return the
/// next pc that is not a no-op instruction.
pub fn skip(&self, mut pc: usize) -> usize {
loop {
match self[pc] {
Inst::Save(ref i) => pc = i.goto,
_ => return pc,
}
}
}
/// Return true if and only if an execution engine at instruction `pc` will
/// always lead to a match.
pub fn leads_to_match(&self, pc: usize) -> bool {
if self.matches.len() > 1 {
// If we have a regex set, then we have more than one ending
// state, so leading to one of those states is generally
// meaningless.
return false;
}
match self[self.skip(pc)] {
Inst::Match(_) => true,
_ => false,
}
}
/// Returns true if the current configuration demands that an implicit
/// `.*?` be prepended to the instruction sequence.
pub fn needs_dotstar(&self) -> bool {
self.is_dfa && !self.is_reverse && !self.is_anchored_start
}
/// Returns true if this program uses Byte instructions instead of
/// Char/Range instructions.
pub fn uses_bytes(&self) -> bool {
self.is_bytes || self.is_dfa
}
/// Returns true if this program exclusively matches valid UTF-8 bytes.
///
/// That is, if an invalid UTF-8 byte is seen, then no match is possible.
pub fn only_utf8(&self) -> bool {
self.only_utf8
}
/// Return the approximate heap usage of this instruction sequence in
/// bytes.
pub fn approximate_size(&self) -> usize {
// The only instruction that uses heap space is Ranges (for
// Unicode codepoint programs) to store non-overlapping codepoint
// ranges. To keep this operation constant time, we ignore them.
(self.len() * mem::size_of::<Inst>())
+ (self.matches.len() * mem::size_of::<InstPtr>())
+ (self.captures.len() * mem::size_of::<Option<String>>())
+ (self.capture_name_idx.len()
* (mem::size_of::<String>() + mem::size_of::<usize>()))
+ (self.byte_classes.len() * mem::size_of::<u8>())
+ self.prefixes.approximate_size()
}
}
impl Deref for Program {
type Target = [Inst];
#[cfg_attr(feature = "perf-inline", inline(always))]
fn deref(&self) -> &Self::Target {
&*self.insts
}
}
impl fmt::Debug for Program {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
use self::Inst::*;
fn with_goto(cur: usize, goto: usize, fmtd: String) -> String {
if goto == cur + 1 {
fmtd
} else {
format!("{} (goto: {})", fmtd, goto)
}
}
fn visible_byte(b: u8) -> String {
use std::ascii::escape_default;
let escaped = escape_default(b).collect::<Vec<u8>>();
String::from_utf8_lossy(&escaped).into_owned()
}
for (pc, inst) in self.iter().enumerate() {
match *inst {
Match(slot) => write!(f, "{:04} Match({:?})", pc, slot)?,
Save(ref inst) => {
let s = format!("{:04} Save({})", pc, inst.slot);
write!(f, "{}", with_goto(pc, inst.goto, s))?;
}
Split(ref inst) => {
write!(
f,
"{:04} Split({}, {})",
pc, inst.goto1, inst.goto2
)?;
}
EmptyLook(ref inst) => {
let s = format!("{:?}", inst.look);
write!(f, "{:04} {}", pc, with_goto(pc, inst.goto, s))?;
}
Char(ref inst) => {
let s = format!("{:?}", inst.c);
write!(f, "{:04} {}", pc, with_goto(pc, inst.goto, s))?;
}
Ranges(ref inst) => {
let ranges = inst
.ranges
.iter()
.map(|r| format!("{:?}-{:?}", r.0, r.1))
.collect::<Vec<String>>()
.join(", ");
write!(
f,
"{:04} {}",
pc,
with_goto(pc, inst.goto, ranges)
)?;
}
Bytes(ref inst) => {
let s = format!(
"Bytes({}, {})",
visible_byte(inst.start),
visible_byte(inst.end)
);
write!(f, "{:04} {}", pc, with_goto(pc, inst.goto, s))?;
}
}
if pc == self.start {
write!(f, " (start)")?;
}
writeln!(f)?;
}
Ok(())
}
}
impl<'a> IntoIterator for &'a Program {
type Item = &'a Inst;
type IntoIter = slice::Iter<'a, Inst>;
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
/// Inst is an instruction code in a Regex program.
///
/// Regrettably, a regex program either contains Unicode codepoint
/// instructions (Char and Ranges) or it contains byte instructions (Bytes).
/// A regex program can never contain both.
///
/// It would be worth investigating splitting this into two distinct types and
/// then figuring out how to make the matching engines polymorphic over those
/// types without sacrificing performance.
///
/// Other than the benefit of moving invariants into the type system, another
/// benefit is the decreased size. If we remove the `Char` and `Ranges`
/// instructions from the `Inst` enum, then its size shrinks from 32 bytes to
/// 24 bytes. (This is because of the removal of a `Box<[]>` in the `Ranges`
/// variant.) Given that byte based machines are typically much bigger than
/// their Unicode analogues (because they can decode UTF-8 directly), this ends
/// up being a pretty significant savings.
#[derive(Clone, Debug)]
pub enum Inst {
/// Match indicates that the program has reached a match state.
///
/// The number in the match corresponds to the Nth logical regular
/// expression in this program. This index is always 0 for normal regex
/// programs. Values greater than 0 appear when compiling regex sets, and
/// each match instruction gets its own unique value. The value corresponds
/// to the Nth regex in the set.
Match(usize),
/// Save causes the program to save the current location of the input in
/// the slot indicated by InstSave.
Save(InstSave),
/// Split causes the program to diverge to one of two paths in the
/// program, preferring goto1 in InstSplit.
Split(InstSplit),
/// EmptyLook represents a zero-width assertion in a regex program. A
/// zero-width assertion does not consume any of the input text.
EmptyLook(InstEmptyLook),
/// Char requires the regex program to match the character in InstChar at
/// the current position in the input.
Char(InstChar),
/// Ranges requires the regex program to match the character at the current
/// position in the input with one of the ranges specified in InstRanges.
Ranges(InstRanges),
/// Bytes is like Ranges, except it expresses a single byte range. It is
/// used in conjunction with Split instructions to implement multi-byte
/// character classes.
Bytes(InstBytes),
}
impl Inst {
/// Returns true if and only if this is a match instruction.
pub fn is_match(&self) -> bool {
match *self {
Inst::Match(_) => true,
_ => false,
}
}
}
/// Representation of the Save instruction.
#[derive(Clone, Debug)]
pub struct InstSave {
/// The next location to execute in the program.
pub goto: InstPtr,
/// The capture slot (there are two slots for every capture in a regex,
/// including the zeroth capture for the entire match).
pub slot: usize,
}
/// Representation of the Split instruction.
#[derive(Clone, Debug)]
pub struct InstSplit {
/// The first instruction to try. A match resulting from following goto1
/// has precedence over a match resulting from following goto2.
pub goto1: InstPtr,
/// The second instruction to try. A match resulting from following goto1
/// has precedence over a match resulting from following goto2.
pub goto2: InstPtr,
}
/// Representation of the `EmptyLook` instruction.
#[derive(Clone, Debug)]
pub struct InstEmptyLook {
/// The next location to execute in the program if this instruction
/// succeeds.
pub goto: InstPtr,
/// The type of zero-width assertion to check.
pub look: EmptyLook,
}
/// The set of zero-width match instructions.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum EmptyLook {
/// Start of line or input.
StartLine,
/// End of line or input.
EndLine,
/// Start of input.
StartText,
/// End of input.
EndText,
/// Word character on one side and non-word character on other.
WordBoundary,
/// Word character on both sides or non-word character on both sides.
NotWordBoundary,
/// ASCII word boundary.
WordBoundaryAscii,
/// Not ASCII word boundary.
NotWordBoundaryAscii,
}
/// Representation of the Char instruction.
#[derive(Clone, Debug)]
pub struct InstChar {
/// The next location to execute in the program if this instruction
/// succeeds.
pub goto: InstPtr,
/// The character to test.
pub c: char,
}
/// Representation of the Ranges instruction.
#[derive(Clone, Debug)]
pub struct InstRanges {
/// The next location to execute in the program if this instruction
/// succeeds.
pub goto: InstPtr,
/// The set of Unicode scalar value ranges to test.
pub ranges: Box<[(char, char)]>,
}
impl InstRanges {
/// Tests whether the given input character matches this instruction.
pub fn matches(&self, c: Char) -> bool {
// This speeds up the `match_class_unicode` benchmark by checking
// some common cases quickly without binary search. e.g., Matching
// a Unicode class on predominantly ASCII text.
for r in self.ranges.iter().take(4) {
if c < r.0 {
return false;
}
if c <= r.1 {
return true;
}
}
self.ranges
.binary_search_by(|r| {
if r.1 < c {
Ordering::Less
} else if r.0 > c {
Ordering::Greater
} else {
Ordering::Equal
}
})
.is_ok()
}
/// Return the number of distinct characters represented by all of the
/// ranges.
pub fn num_chars(&self) -> usize {
self.ranges
.iter()
.map(|&(s, e)| 1 + (e as u32) - (s as u32))
.sum::<u32>() as usize
}
}
/// Representation of the Bytes instruction.
#[derive(Clone, Debug)]
pub struct InstBytes {
/// The next location to execute in the program if this instruction
/// succeeds.
pub goto: InstPtr,
/// The start (inclusive) of this byte range.
pub start: u8,
/// The end (inclusive) of this byte range.
pub end: u8,
}
impl InstBytes {
/// Returns true if and only if the given byte is in this range.
pub fn matches(&self, byte: u8) -> bool {
self.start <= byte && byte <= self.end
}
}
#[cfg(test)]
mod test {
#[test]
#[cfg(target_pointer_width = "64")]
fn test_size_of_inst() {
use std::mem::size_of;
use super::Inst;
assert_eq!(32, size_of::<Inst>());
}
}