Bug Summary

File:llvm/include/llvm/ADT/edit_distance.h
Warning:line 96, column 3
Assigned value is garbage or undefined

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name StringRef.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-11/lib/clang/11.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Support -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Support -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/include -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Support -fdebug-prefix-map=/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-03-09-184146-41876-1 -x c++ /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Support/StringRef.cpp

/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Support/StringRef.cpp

→
1//===-- StringRef.cpp - Lightweight String References ---------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/ADT/StringRef.h"
10#include "llvm/ADT/APFloat.h"
11#include "llvm/ADT/APInt.h"
12#include "llvm/ADT/Hashing.h"
13#include "llvm/ADT/StringExtras.h"
14#include "llvm/ADT/edit_distance.h"
15#include "llvm/Support/Error.h"
16#include <bitset>
17
18using namespace llvm;
19
20// MSVC emits references to this into the translation units which reference it.
21#ifndef _MSC_VER
22const size_t StringRef::npos;
23#endif
24
25// strncasecmp() is not available on non-POSIX systems, so define an
26// alternative function here.
27static int ascii_strncasecmp(const char *LHS, const char *RHS, size_t Length) {
28 for (size_t I = 0; I < Length; ++I) {
29 unsigned char LHC = toLower(LHS[I]);
30 unsigned char RHC = toLower(RHS[I]);
31 if (LHC != RHC)
32 return LHC < RHC ? -1 : 1;
33 }
34 return 0;
35}
36
37/// compare_lower - Compare strings, ignoring case.
38int StringRef::compare_lower(StringRef RHS) const {
39 if (int Res = ascii_strncasecmp(Data, RHS.Data, std::min(Length, RHS.Length)))
40 return Res;
41 if (Length == RHS.Length)
42 return 0;
43 return Length < RHS.Length ? -1 : 1;
44}
45
46/// Check if this string starts with the given \p Prefix, ignoring case.
47bool StringRef::startswith_lower(StringRef Prefix) const {
48 return Length >= Prefix.Length &&
49 ascii_strncasecmp(Data, Prefix.Data, Prefix.Length) == 0;
50}
51
52/// Check if this string ends with the given \p Suffix, ignoring case.
53bool StringRef::endswith_lower(StringRef Suffix) const {
54 return Length >= Suffix.Length &&
55 ascii_strncasecmp(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
56}
57
58size_t StringRef::find_lower(char C, size_t From) const {
59 char L = toLower(C);
60 return find_if([L](char D) { return toLower(D) == L; }, From);
61}
62
63/// compare_numeric - Compare strings, handle embedded numbers.
64int StringRef::compare_numeric(StringRef RHS) const {
65 for (size_t I = 0, E = std::min(Length, RHS.Length); I != E; ++I) {
66 // Check for sequences of digits.
67 if (isDigit(Data[I]) && isDigit(RHS.Data[I])) {
68 // The longer sequence of numbers is considered larger.
69 // This doesn't really handle prefixed zeros well.
70 size_t J;
71 for (J = I + 1; J != E + 1; ++J) {
72 bool ld = J < Length && isDigit(Data[J]);
73 bool rd = J < RHS.Length && isDigit(RHS.Data[J]);
74 if (ld != rd)
75 return rd ? -1 : 1;
76 if (!rd)
77 break;
78 }
79 // The two number sequences have the same length (J-I), just memcmp them.
80 if (int Res = compareMemory(Data + I, RHS.Data + I, J - I))
81 return Res < 0 ? -1 : 1;
82 // Identical number sequences, continue search after the numbers.
83 I = J - 1;
84 continue;
85 }
86 if (Data[I] != RHS.Data[I])
87 return (unsigned char)Data[I] < (unsigned char)RHS.Data[I] ? -1 : 1;
88 }
89 if (Length == RHS.Length)
90 return 0;
91 return Length < RHS.Length ? -1 : 1;
92}
93
94// Compute the edit distance between the two given strings.
95unsigned StringRef::edit_distance(llvm::StringRef Other,
96 bool AllowReplacements,
97 unsigned MaxEditDistance) const {
98 return llvm::ComputeEditDistance(
1
Calling 'ComputeEditDistance<char>'
→
99 makeArrayRef(data(), size()),
100 makeArrayRef(Other.data(), Other.size()),
101 AllowReplacements, MaxEditDistance);
102}
103
104//===----------------------------------------------------------------------===//
105// String Operations
106//===----------------------------------------------------------------------===//
107
108std::string StringRef::lower() const {
109 std::string Result(size(), char());
110 for (size_type i = 0, e = size(); i != e; ++i) {
111 Result[i] = toLower(Data[i]);
112 }
113 return Result;
114}
115
116std::string StringRef::upper() const {
117 std::string Result(size(), char());
118 for (size_type i = 0, e = size(); i != e; ++i) {
119 Result[i] = toUpper(Data[i]);
120 }
121 return Result;
122}
123
124//===----------------------------------------------------------------------===//
125// String Searching
126//===----------------------------------------------------------------------===//
127
128
129/// find - Search for the first string \arg Str in the string.
130///
131/// \return - The index of the first occurrence of \arg Str, or npos if not
132/// found.
133size_t StringRef::find(StringRef Str, size_t From) const {
134 if (From > Length)
135 return npos;
136
137 const char *Start = Data + From;
138 size_t Size = Length - From;
139
140 const char *Needle = Str.data();
141 size_t N = Str.size();
142 if (N == 0)
143 return From;
144 if (Size < N)
145 return npos;
146 if (N == 1) {
147 const char *Ptr = (const char *)::memchr(Start, Needle[0], Size);
148 return Ptr == nullptr ? npos : Ptr - Data;
149 }
150
151 const char *Stop = Start + (Size - N + 1);
152
153 // For short haystacks or unsupported needles fall back to the naive algorithm
154 if (Size < 16 || N > 255) {
155 do {
156 if (std::memcmp(Start, Needle, N) == 0)
157 return Start - Data;
158 ++Start;
159 } while (Start < Stop);
160 return npos;
161 }
162
163 // Build the bad char heuristic table, with uint8_t to reduce cache thrashing.
164 uint8_t BadCharSkip[256];
165 std::memset(BadCharSkip, N, 256);
166 for (unsigned i = 0; i != N-1; ++i)
167 BadCharSkip[(uint8_t)Str[i]] = N-1-i;
168
169 do {
170 uint8_t Last = Start[N - 1];
171 if (LLVM_UNLIKELY(Last == (uint8_t)Needle[N - 1])__builtin_expect((bool)(Last == (uint8_t)Needle[N - 1]), false
))
172 if (std::memcmp(Start, Needle, N - 1) == 0)
173 return Start - Data;
174
175 // Otherwise skip the appropriate number of bytes.
176 Start += BadCharSkip[Last];
177 } while (Start < Stop);
178
179 return npos;
180}
181
182size_t StringRef::find_lower(StringRef Str, size_t From) const {
183 StringRef This = substr(From);
184 while (This.size() >= Str.size()) {
185 if (This.startswith_lower(Str))
186 return From;
187 This = This.drop_front();
188 ++From;
189 }
190 return npos;
191}
192
193size_t StringRef::rfind_lower(char C, size_t From) const {
194 From = std::min(From, Length);
195 size_t i = From;
196 while (i != 0) {
197 --i;
198 if (toLower(Data[i]) == toLower(C))
199 return i;
200 }
201 return npos;
202}
203
204/// rfind - Search for the last string \arg Str in the string.
205///
206/// \return - The index of the last occurrence of \arg Str, or npos if not
207/// found.
208size_t StringRef::rfind(StringRef Str) const {
209 size_t N = Str.size();
210 if (N > Length)
211 return npos;
212 for (size_t i = Length - N + 1, e = 0; i != e;) {
213 --i;
214 if (substr(i, N).equals(Str))
215 return i;
216 }
217 return npos;
218}
219
220size_t StringRef::rfind_lower(StringRef Str) const {
221 size_t N = Str.size();
222 if (N > Length)
223 return npos;
224 for (size_t i = Length - N + 1, e = 0; i != e;) {
225 --i;
226 if (substr(i, N).equals_lower(Str))
227 return i;
228 }
229 return npos;
230}
231
232/// find_first_of - Find the first character in the string that is in \arg
233/// Chars, or npos if not found.
234///
235/// Note: O(size() + Chars.size())
236StringRef::size_type StringRef::find_first_of(StringRef Chars,
237 size_t From) const {
238 std::bitset<1 << CHAR_BIT8> CharBits;
239 for (size_type i = 0; i != Chars.size(); ++i)
240 CharBits.set((unsigned char)Chars[i]);
241
242 for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
243 if (CharBits.test((unsigned char)Data[i]))
244 return i;
245 return npos;
246}
247
248/// find_first_not_of - Find the first character in the string that is not
249/// \arg C or npos if not found.
250StringRef::size_type StringRef::find_first_not_of(char C, size_t From) const {
251 for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
252 if (Data[i] != C)
253 return i;
254 return npos;
255}
256
257/// find_first_not_of - Find the first character in the string that is not
258/// in the string \arg Chars, or npos if not found.
259///
260/// Note: O(size() + Chars.size())
261StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
262 size_t From) const {
263 std::bitset<1 << CHAR_BIT8> CharBits;
264 for (size_type i = 0; i != Chars.size(); ++i)
265 CharBits.set((unsigned char)Chars[i]);
266
267 for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
268 if (!CharBits.test((unsigned char)Data[i]))
269 return i;
270 return npos;
271}
272
273/// find_last_of - Find the last character in the string that is in \arg C,
274/// or npos if not found.
275///
276/// Note: O(size() + Chars.size())
277StringRef::size_type StringRef::find_last_of(StringRef Chars,
278 size_t From) const {
279 std::bitset<1 << CHAR_BIT8> CharBits;
280 for (size_type i = 0; i != Chars.size(); ++i)
281 CharBits.set((unsigned char)Chars[i]);
282
283 for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
284 if (CharBits.test((unsigned char)Data[i]))
285 return i;
286 return npos;
287}
288
289/// find_last_not_of - Find the last character in the string that is not
290/// \arg C, or npos if not found.
291StringRef::size_type StringRef::find_last_not_of(char C, size_t From) const {
292 for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
293 if (Data[i] != C)
294 return i;
295 return npos;
296}
297
298/// find_last_not_of - Find the last character in the string that is not in
299/// \arg Chars, or npos if not found.
300///
301/// Note: O(size() + Chars.size())
302StringRef::size_type StringRef::find_last_not_of(StringRef Chars,
303 size_t From) const {
304 std::bitset<1 << CHAR_BIT8> CharBits;
305 for (size_type i = 0, e = Chars.size(); i != e; ++i)
306 CharBits.set((unsigned char)Chars[i]);
307
308 for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
309 if (!CharBits.test((unsigned char)Data[i]))
310 return i;
311 return npos;
312}
313
314void StringRef::split(SmallVectorImpl<StringRef> &A,
315 StringRef Separator, int MaxSplit,
316 bool KeepEmpty) const {
317 StringRef S = *this;
318
319 // Count down from MaxSplit. When MaxSplit is -1, this will just split
320 // "forever". This doesn't support splitting more than 2^31 times
321 // intentionally; if we ever want that we can make MaxSplit a 64-bit integer
322 // but that seems unlikely to be useful.
323 while (MaxSplit-- != 0) {
324 size_t Idx = S.find(Separator);
325 if (Idx == npos)
326 break;
327
328 // Push this split.
329 if (KeepEmpty || Idx > 0)
330 A.push_back(S.slice(0, Idx));
331
332 // Jump forward.
333 S = S.slice(Idx + Separator.size(), npos);
334 }
335
336 // Push the tail.
337 if (KeepEmpty || !S.empty())
338 A.push_back(S);
339}
340
341void StringRef::split(SmallVectorImpl<StringRef> &A, char Separator,
342 int MaxSplit, bool KeepEmpty) const {
343 StringRef S = *this;
344
345 // Count down from MaxSplit. When MaxSplit is -1, this will just split
346 // "forever". This doesn't support splitting more than 2^31 times
347 // intentionally; if we ever want that we can make MaxSplit a 64-bit integer
348 // but that seems unlikely to be useful.
349 while (MaxSplit-- != 0) {
350 size_t Idx = S.find(Separator);
351 if (Idx == npos)
352 break;
353
354 // Push this split.
355 if (KeepEmpty || Idx > 0)
356 A.push_back(S.slice(0, Idx));
357
358 // Jump forward.
359 S = S.slice(Idx + 1, npos);
360 }
361
362 // Push the tail.
363 if (KeepEmpty || !S.empty())
364 A.push_back(S);
365}
366
367//===----------------------------------------------------------------------===//
368// Helpful Algorithms
369//===----------------------------------------------------------------------===//
370
371/// count - Return the number of non-overlapped occurrences of \arg Str in
372/// the string.
373size_t StringRef::count(StringRef Str) const {
374 size_t Count = 0;
375 size_t N = Str.size();
376 if (!N || N > Length)
377 return 0;
378 for (size_t i = 0, e = Length - N + 1; i < e;) {
379 if (substr(i, N).equals(Str)) {
380 ++Count;
381 i += N;
382 }
383 else
384 ++i;
385 }
386 return Count;
387}
388
389static unsigned GetAutoSenseRadix(StringRef &Str) {
390 if (Str.empty())
391 return 10;
392
393 if (Str.startswith("0x") || Str.startswith("0X")) {
394 Str = Str.substr(2);
395 return 16;
396 }
397
398 if (Str.startswith("0b") || Str.startswith("0B")) {
399 Str = Str.substr(2);
400 return 2;
401 }
402
403 if (Str.startswith("0o")) {
404 Str = Str.substr(2);
405 return 8;
406 }
407
408 if (Str[0] == '0' && Str.size() > 1 && isDigit(Str[1])) {
409 Str = Str.substr(1);
410 return 8;
411 }
412
413 return 10;
414}
415
416bool llvm::consumeUnsignedInteger(StringRef &Str, unsigned Radix,
417 unsigned long long &Result) {
418 // Autosense radix if not specified.
419 if (Radix == 0)
420 Radix = GetAutoSenseRadix(Str);
421
422 // Empty strings (after the radix autosense) are invalid.
423 if (Str.empty()) return true;
424
425 // Parse all the bytes of the string given this radix. Watch for overflow.
426 StringRef Str2 = Str;
427 Result = 0;
428 while (!Str2.empty()) {
429 unsigned CharVal;
430 if (Str2[0] >= '0' && Str2[0] <= '9')
431 CharVal = Str2[0] - '0';
432 else if (Str2[0] >= 'a' && Str2[0] <= 'z')
433 CharVal = Str2[0] - 'a' + 10;
434 else if (Str2[0] >= 'A' && Str2[0] <= 'Z')
435 CharVal = Str2[0] - 'A' + 10;
436 else
437 break;
438
439 // If the parsed value is larger than the integer radix, we cannot
440 // consume any more characters.
441 if (CharVal >= Radix)
442 break;
443
444 // Add in this character.
445 unsigned long long PrevResult = Result;
446 Result = Result * Radix + CharVal;
447
448 // Check for overflow by shifting back and seeing if bits were lost.
449 if (Result / Radix < PrevResult)
450 return true;
451
452 Str2 = Str2.substr(1);
453 }
454
455 // We consider the operation a failure if no characters were consumed
456 // successfully.
457 if (Str.size() == Str2.size())
458 return true;
459
460 Str = Str2;
461 return false;
462}
463
464bool llvm::consumeSignedInteger(StringRef &Str, unsigned Radix,
465 long long &Result) {
466 unsigned long long ULLVal;
467
468 // Handle positive strings first.
469 if (Str.empty() || Str.front() != '-') {
470 if (consumeUnsignedInteger(Str, Radix, ULLVal) ||
471 // Check for value so large it overflows a signed value.
472 (long long)ULLVal < 0)
473 return true;
474 Result = ULLVal;
475 return false;
476 }
477
478 // Get the positive part of the value.
479 StringRef Str2 = Str.drop_front(1);
480 if (consumeUnsignedInteger(Str2, Radix, ULLVal) ||
481 // Reject values so large they'd overflow as negative signed, but allow
482 // "-0". This negates the unsigned so that the negative isn't undefined
483 // on signed overflow.
484 (long long)-ULLVal > 0)
485 return true;
486
487 Str = Str2;
488 Result = -ULLVal;
489 return false;
490}
491
492/// GetAsUnsignedInteger - Workhorse method that converts a integer character
493/// sequence of radix up to 36 to an unsigned long long value.
494bool llvm::getAsUnsignedInteger(StringRef Str, unsigned Radix,
495 unsigned long long &Result) {
496 if (consumeUnsignedInteger(Str, Radix, Result))
497 return true;
498
499 // For getAsUnsignedInteger, we require the whole string to be consumed or
500 // else we consider it a failure.
501 return !Str.empty();
502}
503
504bool llvm::getAsSignedInteger(StringRef Str, unsigned Radix,
505 long long &Result) {
506 if (consumeSignedInteger(Str, Radix, Result))
507 return true;
508
509 // For getAsSignedInteger, we require the whole string to be consumed or else
510 // we consider it a failure.
511 return !Str.empty();
512}
513
514bool StringRef::getAsInteger(unsigned Radix, APInt &Result) const {
515 StringRef Str = *this;
516
517 // Autosense radix if not specified.
518 if (Radix == 0)
519 Radix = GetAutoSenseRadix(Str);
520
521 assert(Radix > 1 && Radix <= 36)((Radix > 1 && Radix <= 36) ? static_cast<void
> (0) : __assert_fail ("Radix > 1 && Radix <= 36"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Support/StringRef.cpp"
, 521, __PRETTY_FUNCTION__));
522
523 // Empty strings (after the radix autosense) are invalid.
524 if (Str.empty()) return true;
525
526 // Skip leading zeroes. This can be a significant improvement if
527 // it means we don't need > 64 bits.
528 while (!Str.empty() && Str.front() == '0')
529 Str = Str.substr(1);
530
531 // If it was nothing but zeroes....
532 if (Str.empty()) {
533 Result = APInt(64, 0);
534 return false;
535 }
536
537 // (Over-)estimate the required number of bits.
538 unsigned Log2Radix = 0;
539 while ((1U << Log2Radix) < Radix) Log2Radix++;
540 bool IsPowerOf2Radix = ((1U << Log2Radix) == Radix);
541
542 unsigned BitWidth = Log2Radix * Str.size();
543 if (BitWidth < Result.getBitWidth())
544 BitWidth = Result.getBitWidth(); // don't shrink the result
545 else if (BitWidth > Result.getBitWidth())
546 Result = Result.zext(BitWidth);
547
548 APInt RadixAP, CharAP; // unused unless !IsPowerOf2Radix
549 if (!IsPowerOf2Radix) {
550 // These must have the same bit-width as Result.
551 RadixAP = APInt(BitWidth, Radix);
552 CharAP = APInt(BitWidth, 0);
553 }
554
555 // Parse all the bytes of the string given this radix.
556 Result = 0;
557 while (!Str.empty()) {
558 unsigned CharVal;
559 if (Str[0] >= '0' && Str[0] <= '9')
560 CharVal = Str[0]-'0';
561 else if (Str[0] >= 'a' && Str[0] <= 'z')
562 CharVal = Str[0]-'a'+10;
563 else if (Str[0] >= 'A' && Str[0] <= 'Z')
564 CharVal = Str[0]-'A'+10;
565 else
566 return true;
567
568 // If the parsed value is larger than the integer radix, the string is
569 // invalid.
570 if (CharVal >= Radix)
571 return true;
572
573 // Add in this character.
574 if (IsPowerOf2Radix) {
575 Result <<= Log2Radix;
576 Result |= CharVal;
577 } else {
578 Result *= RadixAP;
579 CharAP = CharVal;
580 Result += CharAP;
581 }
582
583 Str = Str.substr(1);
584 }
585
586 return false;
587}
588
589bool StringRef::getAsDouble(double &Result, bool AllowInexact) const {
590 APFloat F(0.0);
591 auto StatusOrErr = F.convertFromString(*this, APFloat::rmNearestTiesToEven);
592 if (errorToBool(StatusOrErr.takeError()))
593 return true;
594
595 APFloat::opStatus Status = *StatusOrErr;
596 if (Status != APFloat::opOK) {
597 if (!AllowInexact || !(Status & APFloat::opInexact))
598 return true;
599 }
600
601 Result = F.convertToDouble();
602 return false;
603}
604
605// Implementation of StringRef hashing.
606hash_code llvm::hash_value(StringRef S) {
607 return hash_combine_range(S.begin(), S.end());
608}
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/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/include/llvm/ADT/edit_distance.h

1//===-- llvm/ADT/edit_distance.h - Array edit distance function --- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines a Levenshtein distance function that works for any two
10// sequences, with each element of each sequence being analogous to a character
11// in a string.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ADT_EDIT_DISTANCE_H
16#define LLVM_ADT_EDIT_DISTANCE_H
17
18#include "llvm/ADT/ArrayRef.h"
19#include <algorithm>
20#include <memory>
21
22namespace llvm {
23
24/// Determine the edit distance between two sequences.
25///
26/// \param FromArray the first sequence to compare.
27///
28/// \param ToArray the second sequence to compare.
29///
30/// \param AllowReplacements whether to allow element replacements (change one
31/// element into another) as a single operation, rather than as two operations
32/// (an insertion and a removal).
33///
34/// \param MaxEditDistance If non-zero, the maximum edit distance that this
35/// routine is allowed to compute. If the edit distance will exceed that
36/// maximum, returns \c MaxEditDistance+1.
37///
38/// \returns the minimum number of element insertions, removals, or (if
39/// \p AllowReplacements is \c true) replacements needed to transform one of
40/// the given sequences into the other. If zero, the sequences are identical.
41template<typename T>
42unsigned ComputeEditDistance(ArrayRef<T> FromArray, ArrayRef<T> ToArray,
43 bool AllowReplacements = true,
44 unsigned MaxEditDistance = 0) {
45 // The algorithm implemented below is the "classic"
46 // dynamic-programming algorithm for computing the Levenshtein
47 // distance, which is described here:
48 //
49 // http://en.wikipedia.org/wiki/Levenshtein_distance
50 //
51 // Although the algorithm is typically described using an m x n
52 // array, only one row plus one element are used at a time, so this
53 // implementation just keeps one vector for the row. To update one entry,
54 // only the entries to the left, top, and top-left are needed. The left
55 // entry is in Row[x-1], the top entry is what's in Row[x] from the last
56 // iteration, and the top-left entry is stored in Previous.
57 typename ArrayRef<T>::size_type m = FromArray.size();
58 typename ArrayRef<T>::size_type n = ToArray.size();
2
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'n' initialized here
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59
60 const unsigned SmallBufferSize = 64;
61 unsigned SmallBuffer[SmallBufferSize];
62 std::unique_ptr<unsigned[]> Allocated;
63 unsigned *Row = SmallBuffer;
64 if (n + 1 > SmallBufferSize) {
3
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Assuming the condition is false
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4
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Taking false branch
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65 Row = new unsigned[n + 1];
66 Allocated.reset(Row);
67 }
68
69 for (unsigned i = 1; i <= n; ++i)
5
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Assuming 'i' is > 'n'
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6
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Loop condition is false. Execution continues on line 72
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70 Row[i] = i;
71
72 for (typename ArrayRef<T>::size_type y = 1; y <= m; ++y) {
7
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Assuming 'y' is > 'm'
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8
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Loop condition is false. Execution continues on line 96
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73 Row[0] = y;
74 unsigned BestThisRow = Row[0];
75
76 unsigned Previous = y - 1;
77 for (typename ArrayRef<T>::size_type x = 1; x <= n; ++x) {
78 int OldRow = Row[x];
79 if (AllowReplacements) {
80 Row[x] = std::min(
81 Previous + (FromArray[y-1] == ToArray[x-1] ? 0u : 1u),
82 std::min(Row[x-1], Row[x])+1);
83 }
84 else {
85 if (FromArray[y-1] == ToArray[x-1]) Row[x] = Previous;
86 else Row[x] = std::min(Row[x-1], Row[x]) + 1;
87 }
88 Previous = OldRow;
89 BestThisRow = std::min(BestThisRow, Row[x]);
90 }
91
92 if (MaxEditDistance && BestThisRow > MaxEditDistance)
93 return MaxEditDistance + 1;
94 }
95
96 unsigned Result = Row[n];
9
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Assigned value is garbage or undefined
97 return Result;
98}
99
100} // End llvm namespace
101
102#endif