Chih-Hung Hsieh | e42c505 | 2020-04-16 10:44:21 -0700 | [diff] [blame] | 1 | use std::cmp; |
| 2 | use std::mem; |
| 3 | |
| 4 | use aho_corasick::{self, packed, AhoCorasick, AhoCorasickBuilder}; |
| 5 | use memchr::{memchr, memchr2, memchr3}; |
| 6 | use syntax::hir::literal::{Literal, Literals}; |
| 7 | |
| 8 | use freqs::BYTE_FREQUENCIES; |
| 9 | |
| 10 | /// A prefix extracted from a compiled regular expression. |
| 11 | /// |
| 12 | /// A regex prefix is a set of literal strings that *must* be matched at the |
| 13 | /// beginning of a regex in order for the entire regex to match. Similarly |
| 14 | /// for a regex suffix. |
| 15 | #[derive(Clone, Debug)] |
| 16 | pub struct LiteralSearcher { |
| 17 | complete: bool, |
| 18 | lcp: FreqyPacked, |
| 19 | lcs: FreqyPacked, |
| 20 | matcher: Matcher, |
| 21 | } |
| 22 | |
| 23 | #[derive(Clone, Debug)] |
| 24 | enum Matcher { |
| 25 | /// No literals. (Never advances through the input.) |
| 26 | Empty, |
| 27 | /// A set of four or more single byte literals. |
| 28 | Bytes(SingleByteSet), |
| 29 | /// A single substring, find using memchr and frequency analysis. |
| 30 | FreqyPacked(FreqyPacked), |
| 31 | /// A single substring, find using Boyer-Moore. |
| 32 | BoyerMoore(BoyerMooreSearch), |
| 33 | /// An Aho-Corasick automaton. |
| 34 | AC { ac: AhoCorasick<u32>, lits: Vec<Literal> }, |
| 35 | /// A packed multiple substring searcher, using SIMD. |
| 36 | /// |
| 37 | /// Note that Aho-Corasick will actually use this packed searcher |
| 38 | /// internally automatically, however, there is some overhead associated |
| 39 | /// with going through the Aho-Corasick machinery. So using the packed |
| 40 | /// searcher directly results in some gains. |
| 41 | Packed { s: packed::Searcher, lits: Vec<Literal> }, |
| 42 | } |
| 43 | |
| 44 | impl LiteralSearcher { |
| 45 | /// Returns a matcher that never matches and never advances the input. |
| 46 | pub fn empty() -> Self { |
| 47 | Self::new(Literals::empty(), Matcher::Empty) |
| 48 | } |
| 49 | |
| 50 | /// Returns a matcher for literal prefixes from the given set. |
| 51 | pub fn prefixes(lits: Literals) -> Self { |
| 52 | let matcher = Matcher::prefixes(&lits); |
| 53 | Self::new(lits, matcher) |
| 54 | } |
| 55 | |
| 56 | /// Returns a matcher for literal suffixes from the given set. |
| 57 | pub fn suffixes(lits: Literals) -> Self { |
| 58 | let matcher = Matcher::suffixes(&lits); |
| 59 | Self::new(lits, matcher) |
| 60 | } |
| 61 | |
| 62 | fn new(lits: Literals, matcher: Matcher) -> Self { |
| 63 | let complete = lits.all_complete(); |
| 64 | LiteralSearcher { |
| 65 | complete: complete, |
| 66 | lcp: FreqyPacked::new(lits.longest_common_prefix().to_vec()), |
| 67 | lcs: FreqyPacked::new(lits.longest_common_suffix().to_vec()), |
| 68 | matcher: matcher, |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | /// Returns true if all matches comprise the entire regular expression. |
| 73 | /// |
| 74 | /// This does not necessarily mean that a literal match implies a match |
Haibo Huang | 47619dd | 2021-01-08 17:05:43 -0800 | [diff] [blame^] | 75 | /// of the regular expression. For example, the regular expression `^a` |
Chih-Hung Hsieh | e42c505 | 2020-04-16 10:44:21 -0700 | [diff] [blame] | 76 | /// is comprised of a single complete literal `a`, but the regular |
| 77 | /// expression demands that it only match at the beginning of a string. |
| 78 | pub fn complete(&self) -> bool { |
| 79 | self.complete && !self.is_empty() |
| 80 | } |
| 81 | |
| 82 | /// Find the position of a literal in `haystack` if it exists. |
| 83 | #[cfg_attr(feature = "perf-inline", inline(always))] |
| 84 | pub fn find(&self, haystack: &[u8]) -> Option<(usize, usize)> { |
| 85 | use self::Matcher::*; |
| 86 | match self.matcher { |
| 87 | Empty => Some((0, 0)), |
| 88 | Bytes(ref sset) => sset.find(haystack).map(|i| (i, i + 1)), |
| 89 | FreqyPacked(ref s) => s.find(haystack).map(|i| (i, i + s.len())), |
| 90 | BoyerMoore(ref s) => s.find(haystack).map(|i| (i, i + s.len())), |
| 91 | AC { ref ac, .. } => { |
| 92 | ac.find(haystack).map(|m| (m.start(), m.end())) |
| 93 | } |
| 94 | Packed { ref s, .. } => { |
| 95 | s.find(haystack).map(|m| (m.start(), m.end())) |
| 96 | } |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | /// Like find, except matches must start at index `0`. |
| 101 | pub fn find_start(&self, haystack: &[u8]) -> Option<(usize, usize)> { |
| 102 | for lit in self.iter() { |
| 103 | if lit.len() > haystack.len() { |
| 104 | continue; |
| 105 | } |
| 106 | if lit == &haystack[0..lit.len()] { |
| 107 | return Some((0, lit.len())); |
| 108 | } |
| 109 | } |
| 110 | None |
| 111 | } |
| 112 | |
| 113 | /// Like find, except matches must end at index `haystack.len()`. |
| 114 | pub fn find_end(&self, haystack: &[u8]) -> Option<(usize, usize)> { |
| 115 | for lit in self.iter() { |
| 116 | if lit.len() > haystack.len() { |
| 117 | continue; |
| 118 | } |
| 119 | if lit == &haystack[haystack.len() - lit.len()..] { |
| 120 | return Some((haystack.len() - lit.len(), haystack.len())); |
| 121 | } |
| 122 | } |
| 123 | None |
| 124 | } |
| 125 | |
| 126 | /// Returns an iterator over all literals to be matched. |
| 127 | pub fn iter(&self) -> LiteralIter { |
| 128 | match self.matcher { |
| 129 | Matcher::Empty => LiteralIter::Empty, |
| 130 | Matcher::Bytes(ref sset) => LiteralIter::Bytes(&sset.dense), |
| 131 | Matcher::FreqyPacked(ref s) => LiteralIter::Single(&s.pat), |
| 132 | Matcher::BoyerMoore(ref s) => LiteralIter::Single(&s.pattern), |
| 133 | Matcher::AC { ref lits, .. } => LiteralIter::AC(lits), |
| 134 | Matcher::Packed { ref lits, .. } => LiteralIter::Packed(lits), |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | /// Returns a matcher for the longest common prefix of this matcher. |
| 139 | pub fn lcp(&self) -> &FreqyPacked { |
| 140 | &self.lcp |
| 141 | } |
| 142 | |
| 143 | /// Returns a matcher for the longest common suffix of this matcher. |
| 144 | pub fn lcs(&self) -> &FreqyPacked { |
| 145 | &self.lcs |
| 146 | } |
| 147 | |
| 148 | /// Returns true iff this prefix is empty. |
| 149 | pub fn is_empty(&self) -> bool { |
| 150 | self.len() == 0 |
| 151 | } |
| 152 | |
| 153 | /// Returns the number of prefixes in this machine. |
| 154 | pub fn len(&self) -> usize { |
| 155 | use self::Matcher::*; |
| 156 | match self.matcher { |
| 157 | Empty => 0, |
| 158 | Bytes(ref sset) => sset.dense.len(), |
| 159 | FreqyPacked(_) => 1, |
| 160 | BoyerMoore(_) => 1, |
| 161 | AC { ref ac, .. } => ac.pattern_count(), |
| 162 | Packed { ref lits, .. } => lits.len(), |
| 163 | } |
| 164 | } |
| 165 | |
| 166 | /// Return the approximate heap usage of literals in bytes. |
| 167 | pub fn approximate_size(&self) -> usize { |
| 168 | use self::Matcher::*; |
| 169 | match self.matcher { |
| 170 | Empty => 0, |
| 171 | Bytes(ref sset) => sset.approximate_size(), |
| 172 | FreqyPacked(ref single) => single.approximate_size(), |
| 173 | BoyerMoore(ref single) => single.approximate_size(), |
| 174 | AC { ref ac, .. } => ac.heap_bytes(), |
| 175 | Packed { ref s, .. } => s.heap_bytes(), |
| 176 | } |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | impl Matcher { |
| 181 | fn prefixes(lits: &Literals) -> Self { |
| 182 | let sset = SingleByteSet::prefixes(lits); |
| 183 | Matcher::new(lits, sset) |
| 184 | } |
| 185 | |
| 186 | fn suffixes(lits: &Literals) -> Self { |
| 187 | let sset = SingleByteSet::suffixes(lits); |
| 188 | Matcher::new(lits, sset) |
| 189 | } |
| 190 | |
| 191 | fn new(lits: &Literals, sset: SingleByteSet) -> Self { |
| 192 | if lits.literals().is_empty() { |
| 193 | return Matcher::Empty; |
| 194 | } |
| 195 | if sset.dense.len() >= 26 { |
| 196 | // Avoid trying to match a large number of single bytes. |
| 197 | // This is *very* sensitive to a frequency analysis comparison |
| 198 | // between the bytes in sset and the composition of the haystack. |
| 199 | // No matter the size of sset, if its members all are rare in the |
| 200 | // haystack, then it'd be worth using it. How to tune this... IDK. |
| 201 | // ---AG |
| 202 | return Matcher::Empty; |
| 203 | } |
| 204 | if sset.complete { |
| 205 | return Matcher::Bytes(sset); |
| 206 | } |
| 207 | if lits.literals().len() == 1 { |
| 208 | let lit = lits.literals()[0].to_vec(); |
| 209 | if BoyerMooreSearch::should_use(lit.as_slice()) { |
| 210 | return Matcher::BoyerMoore(BoyerMooreSearch::new(lit)); |
| 211 | } else { |
| 212 | return Matcher::FreqyPacked(FreqyPacked::new(lit)); |
| 213 | } |
| 214 | } |
| 215 | |
| 216 | let pats = lits.literals().to_owned(); |
| 217 | let is_aho_corasick_fast = sset.dense.len() <= 1 && sset.all_ascii; |
| 218 | if lits.literals().len() <= 100 && !is_aho_corasick_fast { |
| 219 | let mut builder = packed::Config::new() |
| 220 | .match_kind(packed::MatchKind::LeftmostFirst) |
| 221 | .builder(); |
| 222 | if let Some(s) = builder.extend(&pats).build() { |
| 223 | return Matcher::Packed { s, lits: pats }; |
| 224 | } |
| 225 | } |
| 226 | let ac = AhoCorasickBuilder::new() |
| 227 | .match_kind(aho_corasick::MatchKind::LeftmostFirst) |
| 228 | .dfa(true) |
| 229 | .build_with_size::<u32, _, _>(&pats) |
| 230 | .unwrap(); |
| 231 | Matcher::AC { ac, lits: pats } |
| 232 | } |
| 233 | } |
| 234 | |
Haibo Huang | 47619dd | 2021-01-08 17:05:43 -0800 | [diff] [blame^] | 235 | #[derive(Debug)] |
Chih-Hung Hsieh | e42c505 | 2020-04-16 10:44:21 -0700 | [diff] [blame] | 236 | pub enum LiteralIter<'a> { |
| 237 | Empty, |
| 238 | Bytes(&'a [u8]), |
| 239 | Single(&'a [u8]), |
| 240 | AC(&'a [Literal]), |
| 241 | Packed(&'a [Literal]), |
| 242 | } |
| 243 | |
| 244 | impl<'a> Iterator for LiteralIter<'a> { |
| 245 | type Item = &'a [u8]; |
| 246 | |
| 247 | fn next(&mut self) -> Option<Self::Item> { |
| 248 | match *self { |
| 249 | LiteralIter::Empty => None, |
| 250 | LiteralIter::Bytes(ref mut many) => { |
| 251 | if many.is_empty() { |
| 252 | None |
| 253 | } else { |
| 254 | let next = &many[0..1]; |
| 255 | *many = &many[1..]; |
| 256 | Some(next) |
| 257 | } |
| 258 | } |
| 259 | LiteralIter::Single(ref mut one) => { |
| 260 | if one.is_empty() { |
| 261 | None |
| 262 | } else { |
| 263 | let next = &one[..]; |
| 264 | *one = &[]; |
| 265 | Some(next) |
| 266 | } |
| 267 | } |
| 268 | LiteralIter::AC(ref mut lits) => { |
| 269 | if lits.is_empty() { |
| 270 | None |
| 271 | } else { |
| 272 | let next = &lits[0]; |
| 273 | *lits = &lits[1..]; |
| 274 | Some(&**next) |
| 275 | } |
| 276 | } |
| 277 | LiteralIter::Packed(ref mut lits) => { |
| 278 | if lits.is_empty() { |
| 279 | None |
| 280 | } else { |
| 281 | let next = &lits[0]; |
| 282 | *lits = &lits[1..]; |
| 283 | Some(&**next) |
| 284 | } |
| 285 | } |
| 286 | } |
| 287 | } |
| 288 | } |
| 289 | |
| 290 | #[derive(Clone, Debug)] |
| 291 | struct SingleByteSet { |
| 292 | sparse: Vec<bool>, |
| 293 | dense: Vec<u8>, |
| 294 | complete: bool, |
| 295 | all_ascii: bool, |
| 296 | } |
| 297 | |
| 298 | impl SingleByteSet { |
| 299 | fn new() -> SingleByteSet { |
| 300 | SingleByteSet { |
| 301 | sparse: vec![false; 256], |
| 302 | dense: vec![], |
| 303 | complete: true, |
| 304 | all_ascii: true, |
| 305 | } |
| 306 | } |
| 307 | |
| 308 | fn prefixes(lits: &Literals) -> SingleByteSet { |
| 309 | let mut sset = SingleByteSet::new(); |
| 310 | for lit in lits.literals() { |
| 311 | sset.complete = sset.complete && lit.len() == 1; |
| 312 | if let Some(&b) = lit.get(0) { |
| 313 | if !sset.sparse[b as usize] { |
| 314 | if b > 0x7F { |
| 315 | sset.all_ascii = false; |
| 316 | } |
| 317 | sset.dense.push(b); |
| 318 | sset.sparse[b as usize] = true; |
| 319 | } |
| 320 | } |
| 321 | } |
| 322 | sset |
| 323 | } |
| 324 | |
| 325 | fn suffixes(lits: &Literals) -> SingleByteSet { |
| 326 | let mut sset = SingleByteSet::new(); |
| 327 | for lit in lits.literals() { |
| 328 | sset.complete = sset.complete && lit.len() == 1; |
| 329 | if let Some(&b) = lit.get(lit.len().checked_sub(1).unwrap()) { |
| 330 | if !sset.sparse[b as usize] { |
| 331 | if b > 0x7F { |
| 332 | sset.all_ascii = false; |
| 333 | } |
| 334 | sset.dense.push(b); |
| 335 | sset.sparse[b as usize] = true; |
| 336 | } |
| 337 | } |
| 338 | } |
| 339 | sset |
| 340 | } |
| 341 | |
| 342 | /// Faster find that special cases certain sizes to use memchr. |
| 343 | #[cfg_attr(feature = "perf-inline", inline(always))] |
| 344 | fn find(&self, text: &[u8]) -> Option<usize> { |
| 345 | match self.dense.len() { |
| 346 | 0 => None, |
| 347 | 1 => memchr(self.dense[0], text), |
| 348 | 2 => memchr2(self.dense[0], self.dense[1], text), |
| 349 | 3 => memchr3(self.dense[0], self.dense[1], self.dense[2], text), |
| 350 | _ => self._find(text), |
| 351 | } |
| 352 | } |
| 353 | |
| 354 | /// Generic find that works on any sized set. |
| 355 | fn _find(&self, haystack: &[u8]) -> Option<usize> { |
| 356 | for (i, &b) in haystack.iter().enumerate() { |
| 357 | if self.sparse[b as usize] { |
| 358 | return Some(i); |
| 359 | } |
| 360 | } |
| 361 | None |
| 362 | } |
| 363 | |
| 364 | fn approximate_size(&self) -> usize { |
| 365 | (self.dense.len() * mem::size_of::<u8>()) |
| 366 | + (self.sparse.len() * mem::size_of::<bool>()) |
| 367 | } |
| 368 | } |
| 369 | |
| 370 | /// Provides an implementation of fast subtring search using frequency |
| 371 | /// analysis. |
| 372 | /// |
| 373 | /// memchr is so fast that we do everything we can to keep the loop in memchr |
| 374 | /// for as long as possible. The easiest way to do this is to intelligently |
| 375 | /// pick the byte to send to memchr. The best byte is the byte that occurs |
| 376 | /// least frequently in the haystack. Since doing frequency analysis on the |
| 377 | /// haystack is far too expensive, we compute a set of fixed frequencies up |
| 378 | /// front and hard code them in src/freqs.rs. Frequency analysis is done via |
| 379 | /// scripts/frequencies.py. |
| 380 | #[derive(Clone, Debug)] |
| 381 | pub struct FreqyPacked { |
| 382 | /// The pattern. |
| 383 | pat: Vec<u8>, |
| 384 | /// The number of Unicode characters in the pattern. This is useful for |
| 385 | /// determining the effective length of a pattern when deciding which |
| 386 | /// optimizations to perform. A trailing incomplete UTF-8 sequence counts |
| 387 | /// as one character. |
| 388 | char_len: usize, |
| 389 | /// The rarest byte in the pattern, according to pre-computed frequency |
| 390 | /// analysis. |
| 391 | rare1: u8, |
| 392 | /// The offset of the rarest byte in `pat`. |
| 393 | rare1i: usize, |
| 394 | /// The second rarest byte in the pattern, according to pre-computed |
| 395 | /// frequency analysis. (This may be equivalent to the rarest byte.) |
| 396 | /// |
| 397 | /// The second rarest byte is used as a type of guard for quickly detecting |
| 398 | /// a mismatch after memchr locates an instance of the rarest byte. This |
| 399 | /// is a hedge against pathological cases where the pre-computed frequency |
| 400 | /// analysis may be off. (But of course, does not prevent *all* |
| 401 | /// pathological cases.) |
| 402 | rare2: u8, |
| 403 | /// The offset of the second rarest byte in `pat`. |
| 404 | rare2i: usize, |
| 405 | } |
| 406 | |
| 407 | impl FreqyPacked { |
| 408 | fn new(pat: Vec<u8>) -> FreqyPacked { |
| 409 | if pat.is_empty() { |
| 410 | return FreqyPacked::empty(); |
| 411 | } |
| 412 | |
| 413 | // Find the rarest two bytes. Try to make them distinct (but it's not |
| 414 | // required). |
| 415 | let mut rare1 = pat[0]; |
| 416 | let mut rare2 = pat[0]; |
| 417 | for b in pat[1..].iter().cloned() { |
| 418 | if freq_rank(b) < freq_rank(rare1) { |
| 419 | rare1 = b; |
| 420 | } |
| 421 | } |
| 422 | for &b in &pat { |
| 423 | if rare1 == rare2 { |
| 424 | rare2 = b |
| 425 | } else if b != rare1 && freq_rank(b) < freq_rank(rare2) { |
| 426 | rare2 = b; |
| 427 | } |
| 428 | } |
| 429 | |
| 430 | // And find the offsets of their last occurrences. |
| 431 | let rare1i = pat.iter().rposition(|&b| b == rare1).unwrap(); |
| 432 | let rare2i = pat.iter().rposition(|&b| b == rare2).unwrap(); |
| 433 | |
| 434 | let char_len = char_len_lossy(&pat); |
| 435 | FreqyPacked { |
| 436 | pat: pat, |
| 437 | char_len: char_len, |
| 438 | rare1: rare1, |
| 439 | rare1i: rare1i, |
| 440 | rare2: rare2, |
| 441 | rare2i: rare2i, |
| 442 | } |
| 443 | } |
| 444 | |
| 445 | fn empty() -> FreqyPacked { |
| 446 | FreqyPacked { |
| 447 | pat: vec![], |
| 448 | char_len: 0, |
| 449 | rare1: 0, |
| 450 | rare1i: 0, |
| 451 | rare2: 0, |
| 452 | rare2i: 0, |
| 453 | } |
| 454 | } |
| 455 | |
| 456 | #[cfg_attr(feature = "perf-inline", inline(always))] |
| 457 | pub fn find(&self, haystack: &[u8]) -> Option<usize> { |
| 458 | let pat = &*self.pat; |
| 459 | if haystack.len() < pat.len() || pat.is_empty() { |
| 460 | return None; |
| 461 | } |
| 462 | let mut i = self.rare1i; |
| 463 | while i < haystack.len() { |
| 464 | i += match memchr(self.rare1, &haystack[i..]) { |
| 465 | None => return None, |
| 466 | Some(i) => i, |
| 467 | }; |
| 468 | let start = i - self.rare1i; |
| 469 | let end = start + pat.len(); |
| 470 | if end > haystack.len() { |
| 471 | return None; |
| 472 | } |
| 473 | let aligned = &haystack[start..end]; |
| 474 | if aligned[self.rare2i] == self.rare2 && aligned == &*self.pat { |
| 475 | return Some(start); |
| 476 | } |
| 477 | i += 1; |
| 478 | } |
| 479 | None |
| 480 | } |
| 481 | |
| 482 | #[cfg_attr(feature = "perf-inline", inline(always))] |
| 483 | pub fn is_suffix(&self, text: &[u8]) -> bool { |
| 484 | if text.len() < self.len() { |
| 485 | return false; |
| 486 | } |
| 487 | text[text.len() - self.len()..] == *self.pat |
| 488 | } |
| 489 | |
| 490 | pub fn len(&self) -> usize { |
| 491 | self.pat.len() |
| 492 | } |
| 493 | |
| 494 | pub fn char_len(&self) -> usize { |
| 495 | self.char_len |
| 496 | } |
| 497 | |
| 498 | fn approximate_size(&self) -> usize { |
| 499 | self.pat.len() * mem::size_of::<u8>() |
| 500 | } |
| 501 | } |
| 502 | |
| 503 | fn char_len_lossy(bytes: &[u8]) -> usize { |
| 504 | String::from_utf8_lossy(bytes).chars().count() |
| 505 | } |
| 506 | |
| 507 | /// An implementation of Tuned Boyer-Moore as laid out by |
| 508 | /// Andrew Hume and Daniel Sunday in "Fast String Searching". |
| 509 | /// O(n) in the size of the input. |
| 510 | /// |
| 511 | /// Fast string searching algorithms come in many variations, |
| 512 | /// but they can generally be described in terms of three main |
| 513 | /// components. |
| 514 | /// |
| 515 | /// The skip loop is where the string searcher wants to spend |
| 516 | /// as much time as possible. Exactly which character in the |
| 517 | /// pattern the skip loop examines varies from algorithm to |
| 518 | /// algorithm, but in the simplest case this loop repeated |
| 519 | /// looks at the last character in the pattern and jumps |
| 520 | /// forward in the input if it is not in the pattern. |
| 521 | /// Robert Boyer and J Moore called this the "fast" loop in |
| 522 | /// their original paper. |
| 523 | /// |
| 524 | /// The match loop is responsible for actually examining the |
| 525 | /// whole potentially matching substring. In order to fail |
| 526 | /// faster, the match loop sometimes has a guard test attached. |
| 527 | /// The guard test uses frequency analysis of the different |
| 528 | /// characters in the pattern to choose the least frequency |
| 529 | /// occurring character and use it to find match failures |
| 530 | /// as quickly as possible. |
| 531 | /// |
| 532 | /// The shift rule governs how the algorithm will shuffle its |
| 533 | /// test window in the event of a failure during the match loop. |
| 534 | /// Certain shift rules allow the worst-case run time of the |
| 535 | /// algorithm to be shown to be O(n) in the size of the input |
| 536 | /// rather than O(nm) in the size of the input and the size |
| 537 | /// of the pattern (as naive Boyer-Moore is). |
| 538 | /// |
| 539 | /// "Fast String Searching", in addition to presenting a tuned |
| 540 | /// algorithm, provides a comprehensive taxonomy of the many |
| 541 | /// different flavors of string searchers. Under that taxonomy |
| 542 | /// TBM, the algorithm implemented here, uses an unrolled fast |
| 543 | /// skip loop with memchr fallback, a forward match loop with guard, |
| 544 | /// and the mini Sunday's delta shift rule. To unpack that you'll have to |
| 545 | /// read the paper. |
| 546 | #[derive(Clone, Debug)] |
| 547 | pub struct BoyerMooreSearch { |
| 548 | /// The pattern we are going to look for in the haystack. |
| 549 | pattern: Vec<u8>, |
| 550 | |
| 551 | /// The skip table for the skip loop. |
| 552 | /// |
| 553 | /// Maps the character at the end of the input |
| 554 | /// to a shift. |
| 555 | skip_table: Vec<usize>, |
| 556 | |
| 557 | /// The guard character (least frequently occurring char). |
| 558 | guard: u8, |
| 559 | /// The reverse-index of the guard character in the pattern. |
| 560 | guard_reverse_idx: usize, |
| 561 | |
| 562 | /// Daniel Sunday's mini generalized delta2 shift table. |
| 563 | /// |
| 564 | /// We use a skip loop, so we only have to provide a shift |
| 565 | /// for the skip char (last char). This is why it is a mini |
| 566 | /// shift rule. |
| 567 | md2_shift: usize, |
| 568 | } |
| 569 | |
| 570 | impl BoyerMooreSearch { |
| 571 | /// Create a new string searcher, performing whatever |
| 572 | /// compilation steps are required. |
| 573 | fn new(pattern: Vec<u8>) -> Self { |
| 574 | debug_assert!(!pattern.is_empty()); |
| 575 | |
| 576 | let (g, gi) = Self::select_guard(pattern.as_slice()); |
| 577 | let skip_table = Self::compile_skip_table(pattern.as_slice()); |
| 578 | let md2_shift = Self::compile_md2_shift(pattern.as_slice()); |
| 579 | BoyerMooreSearch { |
| 580 | pattern: pattern, |
| 581 | skip_table: skip_table, |
| 582 | guard: g, |
| 583 | guard_reverse_idx: gi, |
| 584 | md2_shift: md2_shift, |
| 585 | } |
| 586 | } |
| 587 | |
| 588 | /// Find the pattern in `haystack`, returning the offset |
| 589 | /// of the start of the first occurrence of the pattern |
| 590 | /// in `haystack`. |
| 591 | #[inline] |
| 592 | fn find(&self, haystack: &[u8]) -> Option<usize> { |
| 593 | if haystack.len() < self.pattern.len() { |
| 594 | return None; |
| 595 | } |
| 596 | |
| 597 | let mut window_end = self.pattern.len() - 1; |
| 598 | |
| 599 | // Inspired by the grep source. It is a way |
| 600 | // to do correct loop unrolling without having to place |
| 601 | // a crashpad of terminating charicters at the end in |
| 602 | // the way described in the Fast String Searching paper. |
| 603 | const NUM_UNROLL: usize = 10; |
| 604 | // 1 for the initial position, and 1 for the md2 shift |
| 605 | let short_circut = (NUM_UNROLL + 2) * self.pattern.len(); |
| 606 | |
| 607 | if haystack.len() > short_circut { |
| 608 | // just 1 for the md2 shift |
| 609 | let backstop = |
| 610 | haystack.len() - ((NUM_UNROLL + 1) * self.pattern.len()); |
| 611 | loop { |
| 612 | window_end = |
| 613 | match self.skip_loop(haystack, window_end, backstop) { |
| 614 | Some(i) => i, |
| 615 | None => return None, |
| 616 | }; |
| 617 | if window_end >= backstop { |
| 618 | break; |
| 619 | } |
| 620 | |
| 621 | if self.check_match(haystack, window_end) { |
| 622 | return Some(window_end - (self.pattern.len() - 1)); |
| 623 | } else { |
| 624 | let skip = self.skip_table[haystack[window_end] as usize]; |
| 625 | window_end += |
| 626 | if skip == 0 { self.md2_shift } else { skip }; |
| 627 | continue; |
| 628 | } |
| 629 | } |
| 630 | } |
| 631 | |
| 632 | // now process the input after the backstop |
| 633 | while window_end < haystack.len() { |
| 634 | let mut skip = self.skip_table[haystack[window_end] as usize]; |
| 635 | if skip == 0 { |
| 636 | if self.check_match(haystack, window_end) { |
| 637 | return Some(window_end - (self.pattern.len() - 1)); |
| 638 | } else { |
| 639 | skip = self.md2_shift; |
| 640 | } |
| 641 | } |
| 642 | window_end += skip; |
| 643 | } |
| 644 | |
| 645 | None |
| 646 | } |
| 647 | |
| 648 | fn len(&self) -> usize { |
| 649 | return self.pattern.len(); |
| 650 | } |
| 651 | |
| 652 | /// The key heuristic behind which the BoyerMooreSearch lives. |
| 653 | /// |
| 654 | /// See `rust-lang/regex/issues/408`. |
| 655 | /// |
| 656 | /// Tuned Boyer-Moore is actually pretty slow! It turns out a handrolled |
| 657 | /// platform-specific memchr routine with a bit of frequency |
| 658 | /// analysis sprinkled on top actually wins most of the time. |
| 659 | /// However, there are a few cases where Tuned Boyer-Moore still |
| 660 | /// wins. |
| 661 | /// |
| 662 | /// If the haystack is random, frequency analysis doesn't help us, |
| 663 | /// so Boyer-Moore will win for sufficiently large needles. |
| 664 | /// Unfortunately, there is no obvious way to determine this |
| 665 | /// ahead of time. |
| 666 | /// |
| 667 | /// If the pattern itself consists of very common characters, |
| 668 | /// frequency analysis won't get us anywhere. The most extreme |
| 669 | /// example of this is a pattern like `eeeeeeeeeeeeeeee`. Fortunately, |
| 670 | /// this case is wholly determined by the pattern, so we can actually |
| 671 | /// implement the heuristic. |
| 672 | /// |
| 673 | /// A third case is if the pattern is sufficiently long. The idea |
| 674 | /// here is that once the pattern gets long enough the Tuned |
| 675 | /// Boyer-Moore skip loop will start making strides long enough |
| 676 | /// to beat the asm deep magic that is memchr. |
| 677 | fn should_use(pattern: &[u8]) -> bool { |
| 678 | // The minimum pattern length required to use TBM. |
| 679 | const MIN_LEN: usize = 9; |
| 680 | // The minimum frequency rank (lower is rarer) that every byte in the |
| 681 | // pattern must have in order to use TBM. That is, if the pattern |
| 682 | // contains _any_ byte with a lower rank, then TBM won't be used. |
| 683 | const MIN_CUTOFF: usize = 150; |
| 684 | // The maximum frequency rank for any byte. |
| 685 | const MAX_CUTOFF: usize = 255; |
| 686 | // The scaling factor used to determine the actual cutoff frequency |
| 687 | // to use (keeping in mind that the minimum frequency rank is bounded |
| 688 | // by MIN_CUTOFF). This scaling factor is an attempt to make TBM more |
| 689 | // likely to be used as the pattern grows longer. That is, longer |
| 690 | // patterns permit somewhat less frequent bytes than shorter patterns, |
| 691 | // under the assumption that TBM gets better as the pattern gets |
| 692 | // longer. |
| 693 | const LEN_CUTOFF_PROPORTION: usize = 4; |
| 694 | |
| 695 | let scaled_rank = pattern.len().wrapping_mul(LEN_CUTOFF_PROPORTION); |
| 696 | let cutoff = cmp::max( |
| 697 | MIN_CUTOFF, |
| 698 | MAX_CUTOFF - cmp::min(MAX_CUTOFF, scaled_rank), |
| 699 | ); |
| 700 | // The pattern must be long enough to be worthwhile. e.g., memchr will |
| 701 | // be faster on `e` because it is short even though e is quite common. |
| 702 | pattern.len() > MIN_LEN |
| 703 | // all the bytes must be more common than the cutoff. |
| 704 | && pattern.iter().all(|c| freq_rank(*c) >= cutoff) |
| 705 | } |
| 706 | |
| 707 | /// Check to see if there is a match at the given position |
| 708 | #[inline] |
| 709 | fn check_match(&self, haystack: &[u8], window_end: usize) -> bool { |
| 710 | // guard test |
| 711 | if haystack[window_end - self.guard_reverse_idx] != self.guard { |
| 712 | return false; |
| 713 | } |
| 714 | |
| 715 | // match loop |
| 716 | let window_start = window_end - (self.pattern.len() - 1); |
| 717 | for i in 0..self.pattern.len() { |
| 718 | if self.pattern[i] != haystack[window_start + i] { |
| 719 | return false; |
| 720 | } |
| 721 | } |
| 722 | |
| 723 | true |
| 724 | } |
| 725 | |
| 726 | /// Skip forward according to the shift table. |
| 727 | /// |
| 728 | /// Returns the offset of the next occurrence |
| 729 | /// of the last char in the pattern, or the none |
| 730 | /// if it never reappears. If `skip_loop` hits the backstop |
| 731 | /// it will leave early. |
| 732 | #[inline] |
| 733 | fn skip_loop( |
| 734 | &self, |
| 735 | haystack: &[u8], |
| 736 | mut window_end: usize, |
| 737 | backstop: usize, |
| 738 | ) -> Option<usize> { |
| 739 | let window_end_snapshot = window_end; |
| 740 | let skip_of = |we: usize| -> usize { |
| 741 | // Unsafe might make this faster, but the benchmarks |
| 742 | // were hard to interpret. |
| 743 | self.skip_table[haystack[we] as usize] |
| 744 | }; |
| 745 | |
| 746 | loop { |
| 747 | let mut skip = skip_of(window_end); |
| 748 | window_end += skip; |
| 749 | skip = skip_of(window_end); |
| 750 | window_end += skip; |
| 751 | if skip != 0 { |
| 752 | skip = skip_of(window_end); |
| 753 | window_end += skip; |
| 754 | skip = skip_of(window_end); |
| 755 | window_end += skip; |
| 756 | skip = skip_of(window_end); |
| 757 | window_end += skip; |
| 758 | if skip != 0 { |
| 759 | skip = skip_of(window_end); |
| 760 | window_end += skip; |
| 761 | skip = skip_of(window_end); |
| 762 | window_end += skip; |
| 763 | skip = skip_of(window_end); |
| 764 | window_end += skip; |
| 765 | if skip != 0 { |
| 766 | skip = skip_of(window_end); |
| 767 | window_end += skip; |
| 768 | skip = skip_of(window_end); |
| 769 | window_end += skip; |
| 770 | |
| 771 | // If ten iterations did not make at least 16 words |
| 772 | // worth of progress, we just fall back on memchr. |
| 773 | if window_end - window_end_snapshot |
| 774 | > 16 * mem::size_of::<usize>() |
| 775 | { |
| 776 | // Returning a window_end >= backstop will |
| 777 | // immediatly break us out of the inner loop in |
| 778 | // `find`. |
| 779 | if window_end >= backstop { |
| 780 | return Some(window_end); |
| 781 | } |
| 782 | |
| 783 | continue; // we made enough progress |
| 784 | } else { |
| 785 | // In case we are already there, and so that |
| 786 | // we will catch the guard char. |
| 787 | window_end = window_end |
| 788 | .checked_sub(1 + self.guard_reverse_idx) |
| 789 | .unwrap_or(0); |
| 790 | |
| 791 | match memchr(self.guard, &haystack[window_end..]) { |
| 792 | None => return None, |
| 793 | Some(g_idx) => { |
| 794 | return Some( |
| 795 | window_end |
| 796 | + g_idx |
| 797 | + self.guard_reverse_idx, |
| 798 | ); |
| 799 | } |
| 800 | } |
| 801 | } |
| 802 | } |
| 803 | } |
| 804 | } |
| 805 | |
| 806 | return Some(window_end); |
| 807 | } |
| 808 | } |
| 809 | |
| 810 | /// Compute the ufast skip table. |
| 811 | fn compile_skip_table(pattern: &[u8]) -> Vec<usize> { |
| 812 | let mut tab = vec![pattern.len(); 256]; |
| 813 | |
| 814 | // For every char in the pattern, we write a skip |
| 815 | // that will line us up with the rightmost occurrence. |
| 816 | // |
| 817 | // N.B. the sentinel (0) is written by the last |
| 818 | // loop iteration. |
| 819 | for (i, c) in pattern.iter().enumerate() { |
| 820 | tab[*c as usize] = (pattern.len() - 1) - i; |
| 821 | } |
| 822 | |
| 823 | tab |
| 824 | } |
| 825 | |
| 826 | /// Select the guard character based off of the precomputed |
| 827 | /// frequency table. |
| 828 | fn select_guard(pattern: &[u8]) -> (u8, usize) { |
| 829 | let mut rarest = pattern[0]; |
| 830 | let mut rarest_rev_idx = pattern.len() - 1; |
| 831 | for (i, c) in pattern.iter().enumerate() { |
| 832 | if freq_rank(*c) < freq_rank(rarest) { |
| 833 | rarest = *c; |
| 834 | rarest_rev_idx = (pattern.len() - 1) - i; |
| 835 | } |
| 836 | } |
| 837 | |
| 838 | (rarest, rarest_rev_idx) |
| 839 | } |
| 840 | |
| 841 | /// If there is another occurrence of the skip |
| 842 | /// char, shift to it, otherwise just shift to |
| 843 | /// the next window. |
| 844 | fn compile_md2_shift(pattern: &[u8]) -> usize { |
| 845 | let shiftc = *pattern.last().unwrap(); |
| 846 | |
| 847 | // For a pattern of length 1 we will never apply the |
| 848 | // shift rule, so we use a poison value on the principle |
| 849 | // that failing fast is a good thing. |
| 850 | if pattern.len() == 1 { |
| 851 | return 0xDEADBEAF; |
| 852 | } |
| 853 | |
| 854 | let mut i = pattern.len() - 2; |
| 855 | while i > 0 { |
| 856 | if pattern[i] == shiftc { |
| 857 | return (pattern.len() - 1) - i; |
| 858 | } |
| 859 | i -= 1; |
| 860 | } |
| 861 | |
| 862 | // The skip char never re-occurs in the pattern, so |
| 863 | // we can just shift the whole window length. |
| 864 | pattern.len() - 1 |
| 865 | } |
| 866 | |
| 867 | fn approximate_size(&self) -> usize { |
| 868 | (self.pattern.len() * mem::size_of::<u8>()) |
| 869 | + (256 * mem::size_of::<usize>()) // skip table |
| 870 | } |
| 871 | } |
| 872 | |
| 873 | fn freq_rank(b: u8) -> usize { |
| 874 | BYTE_FREQUENCIES[b as usize] as usize |
| 875 | } |
| 876 | |
| 877 | #[cfg(test)] |
| 878 | mod tests { |
| 879 | use super::{BoyerMooreSearch, FreqyPacked}; |
| 880 | |
| 881 | // |
| 882 | // Unit Tests |
| 883 | // |
| 884 | |
| 885 | // The "hello, world" of string searching |
| 886 | #[test] |
| 887 | fn bm_find_subs() { |
| 888 | let searcher = BoyerMooreSearch::new(Vec::from(&b"pattern"[..])); |
| 889 | let haystack = b"I keep seeing patterns in this text"; |
| 890 | assert_eq!(14, searcher.find(haystack).unwrap()); |
| 891 | } |
| 892 | |
| 893 | #[test] |
| 894 | fn bm_find_no_subs() { |
| 895 | let searcher = BoyerMooreSearch::new(Vec::from(&b"pattern"[..])); |
| 896 | let haystack = b"I keep seeing needles in this text"; |
| 897 | assert_eq!(None, searcher.find(haystack)); |
| 898 | } |
| 899 | |
| 900 | // |
| 901 | // Regression Tests |
| 902 | // |
| 903 | |
| 904 | #[test] |
| 905 | fn bm_skip_reset_bug() { |
| 906 | let haystack = vec![0, 0, 0, 0, 0, 1, 1, 0]; |
| 907 | let needle = vec![0, 1, 1, 0]; |
| 908 | |
| 909 | let searcher = BoyerMooreSearch::new(needle); |
| 910 | let offset = searcher.find(haystack.as_slice()).unwrap(); |
| 911 | assert_eq!(4, offset); |
| 912 | } |
| 913 | |
| 914 | #[test] |
| 915 | fn bm_backstop_underflow_bug() { |
| 916 | let haystack = vec![0, 0]; |
| 917 | let needle = vec![0, 0]; |
| 918 | |
| 919 | let searcher = BoyerMooreSearch::new(needle); |
| 920 | let offset = searcher.find(haystack.as_slice()).unwrap(); |
| 921 | assert_eq!(0, offset); |
| 922 | } |
| 923 | |
| 924 | #[test] |
| 925 | fn bm_naive_off_by_one_bug() { |
| 926 | let haystack = vec![91]; |
| 927 | let needle = vec![91]; |
| 928 | |
| 929 | let naive_offset = naive_find(&needle, &haystack).unwrap(); |
| 930 | assert_eq!(0, naive_offset); |
| 931 | } |
| 932 | |
| 933 | #[test] |
| 934 | fn bm_memchr_fallback_indexing_bug() { |
| 935 | let mut haystack = vec![ |
| 936 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 937 | 0, 0, 0, 0, 0, 87, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 938 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 939 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 940 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 941 | ]; |
| 942 | let needle = vec![1, 1, 1, 1, 32, 32, 87]; |
| 943 | let needle_start = haystack.len(); |
| 944 | haystack.extend(needle.clone()); |
| 945 | |
| 946 | let searcher = BoyerMooreSearch::new(needle); |
| 947 | assert_eq!(needle_start, searcher.find(haystack.as_slice()).unwrap()); |
| 948 | } |
| 949 | |
| 950 | #[test] |
| 951 | fn bm_backstop_boundary() { |
| 952 | let haystack = b"\ |
| 953 | // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
| 954 | e_data.clone_created(entity_id, entity_to_add.entity_id); |
| 955 | aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
| 956 | aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
| 957 | " |
| 958 | .to_vec(); |
| 959 | let needle = b"clone_created".to_vec(); |
| 960 | |
| 961 | let searcher = BoyerMooreSearch::new(needle); |
| 962 | let result = searcher.find(&haystack); |
| 963 | assert_eq!(Some(43), result); |
| 964 | } |
| 965 | |
| 966 | #[test] |
| 967 | fn bm_win_gnu_indexing_bug() { |
| 968 | let haystack_raw = vec![ |
| 969 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 970 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 971 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 972 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, |
| 973 | ]; |
| 974 | let needle = vec![1, 1, 1, 1, 1, 1, 1]; |
| 975 | let haystack = haystack_raw.as_slice(); |
| 976 | |
| 977 | BoyerMooreSearch::new(needle.clone()).find(haystack); |
| 978 | } |
| 979 | |
| 980 | // |
| 981 | // QuickCheck Properties |
| 982 | // |
| 983 | |
| 984 | use quickcheck::TestResult; |
| 985 | |
| 986 | fn naive_find(needle: &[u8], haystack: &[u8]) -> Option<usize> { |
| 987 | assert!(needle.len() <= haystack.len()); |
| 988 | |
| 989 | for i in 0..(haystack.len() - (needle.len() - 1)) { |
| 990 | if haystack[i] == needle[0] |
| 991 | && &haystack[i..(i + needle.len())] == needle |
| 992 | { |
| 993 | return Some(i); |
| 994 | } |
| 995 | } |
| 996 | |
| 997 | None |
| 998 | } |
| 999 | |
| 1000 | quickcheck! { |
| 1001 | fn qc_bm_equals_nieve_find(pile1: Vec<u8>, pile2: Vec<u8>) -> TestResult { |
| 1002 | if pile1.len() == 0 || pile2.len() == 0 { |
| 1003 | return TestResult::discard(); |
| 1004 | } |
| 1005 | |
| 1006 | let (needle, haystack) = if pile1.len() < pile2.len() { |
| 1007 | (pile1, pile2.as_slice()) |
| 1008 | } else { |
| 1009 | (pile2, pile1.as_slice()) |
| 1010 | }; |
| 1011 | |
| 1012 | let searcher = BoyerMooreSearch::new(needle.clone()); |
| 1013 | TestResult::from_bool( |
| 1014 | searcher.find(haystack) == naive_find(&needle, haystack)) |
| 1015 | } |
| 1016 | |
| 1017 | fn qc_bm_equals_single(pile1: Vec<u8>, pile2: Vec<u8>) -> TestResult { |
| 1018 | if pile1.len() == 0 || pile2.len() == 0 { |
| 1019 | return TestResult::discard(); |
| 1020 | } |
| 1021 | |
| 1022 | let (needle, haystack) = if pile1.len() < pile2.len() { |
| 1023 | (pile1, pile2.as_slice()) |
| 1024 | } else { |
| 1025 | (pile2, pile1.as_slice()) |
| 1026 | }; |
| 1027 | |
| 1028 | let bm_searcher = BoyerMooreSearch::new(needle.clone()); |
| 1029 | let freqy_memchr = FreqyPacked::new(needle); |
| 1030 | TestResult::from_bool( |
| 1031 | bm_searcher.find(haystack) == freqy_memchr.find(haystack)) |
| 1032 | } |
| 1033 | |
| 1034 | fn qc_bm_finds_trailing_needle( |
| 1035 | haystack_pre: Vec<u8>, |
| 1036 | needle: Vec<u8> |
| 1037 | ) -> TestResult { |
| 1038 | if needle.len() == 0 { |
| 1039 | return TestResult::discard(); |
| 1040 | } |
| 1041 | |
| 1042 | let mut haystack = haystack_pre.clone(); |
| 1043 | let searcher = BoyerMooreSearch::new(needle.clone()); |
| 1044 | |
| 1045 | if haystack.len() >= needle.len() && |
| 1046 | searcher.find(haystack.as_slice()).is_some() { |
| 1047 | return TestResult::discard(); |
| 1048 | } |
| 1049 | |
| 1050 | haystack.extend(needle.clone()); |
| 1051 | |
| 1052 | // What if the the tail of the haystack can start the |
| 1053 | // needle? |
| 1054 | let start = haystack_pre.len() |
| 1055 | .checked_sub(needle.len()) |
| 1056 | .unwrap_or(0); |
| 1057 | for i in 0..(needle.len() - 1) { |
| 1058 | if searcher.find(&haystack[(i + start)..]).is_some() { |
| 1059 | return TestResult::discard(); |
| 1060 | } |
| 1061 | } |
| 1062 | |
| 1063 | TestResult::from_bool( |
| 1064 | searcher.find(haystack.as_slice()) |
| 1065 | .map(|x| x == haystack_pre.len()) |
| 1066 | .unwrap_or(false)) |
| 1067 | } |
| 1068 | |
| 1069 | // qc_equals_* is only testing the negative case as @burntsushi |
| 1070 | // pointed out in https://github.com/rust-lang/regex/issues/446. |
| 1071 | // This quickcheck prop represents an effort to force testing of |
| 1072 | // the positive case. qc_bm_finds_first and qc_bm_finds_trailing_needle |
| 1073 | // already check some of the positive cases, but they don't cover |
| 1074 | // cases where the needle is in the middle of haystack. This prop |
| 1075 | // fills that hole. |
| 1076 | fn qc_bm_finds_subslice( |
| 1077 | haystack: Vec<u8>, |
| 1078 | needle_start: usize, |
| 1079 | needle_length: usize |
| 1080 | ) -> TestResult { |
| 1081 | if haystack.len() == 0 { |
| 1082 | return TestResult::discard(); |
| 1083 | } |
| 1084 | |
| 1085 | let needle_start = needle_start % haystack.len(); |
| 1086 | let needle_length = needle_length % (haystack.len() - needle_start); |
| 1087 | |
| 1088 | if needle_length == 0 { |
| 1089 | return TestResult::discard(); |
| 1090 | } |
| 1091 | |
| 1092 | let needle = &haystack[needle_start..(needle_start + needle_length)]; |
| 1093 | |
| 1094 | let bm_searcher = BoyerMooreSearch::new(needle.to_vec()); |
| 1095 | |
| 1096 | let start = naive_find(&needle, &haystack); |
| 1097 | match start { |
| 1098 | None => TestResult::from_bool(false), |
| 1099 | Some(nf_start) => |
| 1100 | TestResult::from_bool( |
| 1101 | nf_start <= needle_start |
| 1102 | && bm_searcher.find(&haystack) == start |
| 1103 | ) |
| 1104 | } |
| 1105 | } |
| 1106 | |
| 1107 | fn qc_bm_finds_first(needle: Vec<u8>) -> TestResult { |
| 1108 | if needle.len() == 0 { |
| 1109 | return TestResult::discard(); |
| 1110 | } |
| 1111 | |
| 1112 | let mut haystack = needle.clone(); |
| 1113 | let searcher = BoyerMooreSearch::new(needle.clone()); |
| 1114 | haystack.extend(needle); |
| 1115 | |
| 1116 | TestResult::from_bool( |
| 1117 | searcher.find(haystack.as_slice()) |
| 1118 | .map(|x| x == 0) |
| 1119 | .unwrap_or(false)) |
| 1120 | } |
| 1121 | } |
| 1122 | } |