1//===- FuzzerMutate.cpp - Mutate a test input -----------------------------===//
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// Mutate a test input.
9//===----------------------------------------------------------------------===//
10
11#include "FuzzerDefs.h"
12#include "FuzzerExtFunctions.h"
13#include "FuzzerIO.h"
14#include "FuzzerMutate.h"
15#include "FuzzerOptions.h"
16#include "FuzzerTracePC.h"
17
18namespace fuzzer {
19
20const size_t Dictionary::kMaxDictSize;
21
22static void PrintASCII(const Word &W, const char *PrintAfter) {
23  PrintASCII(W.data(), W.size(), PrintAfter);
24}
25
26MutationDispatcher::MutationDispatcher(Random &Rand,
27                                       const FuzzingOptions &Options)
28    : Rand(Rand), Options(Options) {
29  DefaultMutators.insert(
30      DefaultMutators.begin(),
31      {
32          {&MutationDispatcher::Mutate_EraseBytes, "EraseBytes"},
33          {&MutationDispatcher::Mutate_InsertByte, "InsertByte"},
34          {&MutationDispatcher::Mutate_InsertRepeatedBytes,
35           "InsertRepeatedBytes"},
36          {&MutationDispatcher::Mutate_ChangeByte, "ChangeByte"},
37          {&MutationDispatcher::Mutate_ChangeBit, "ChangeBit"},
38          {&MutationDispatcher::Mutate_ShuffleBytes, "ShuffleBytes"},
39          {&MutationDispatcher::Mutate_ChangeASCIIInteger, "ChangeASCIIInt"},
40          {&MutationDispatcher::Mutate_ChangeBinaryInteger, "ChangeBinInt"},
41          {&MutationDispatcher::Mutate_CopyPart, "CopyPart"},
42          {&MutationDispatcher::Mutate_CrossOver, "CrossOver"},
43          {&MutationDispatcher::Mutate_AddWordFromManualDictionary,
44           "ManualDict"},
45          {&MutationDispatcher::Mutate_AddWordFromPersistentAutoDictionary,
46           "PersAutoDict"},
47      });
48  if(Options.UseCmp)
49    DefaultMutators.push_back(
50        {&MutationDispatcher::Mutate_AddWordFromTORC, "CMP"});
51
52  if (EF->LLVMFuzzerCustomMutator)
53    Mutators.push_back({&MutationDispatcher::Mutate_Custom, "Custom"});
54  else
55    Mutators = DefaultMutators;
56
57  if (EF->LLVMFuzzerCustomCrossOver)
58    Mutators.push_back(
59        {&MutationDispatcher::Mutate_CustomCrossOver, "CustomCrossOver"});
60}
61
62static char RandCh(Random &Rand) {
63  if (Rand.RandBool()) return Rand(256);
64  const char Special[] = "!*'();:@&=+$,/?%#[]012Az-`~.\xff\x00";
65  return Special[Rand(sizeof(Special) - 1)];
66}
67
68size_t MutationDispatcher::Mutate_Custom(uint8_t *Data, size_t Size,
69                                         size_t MaxSize) {
70  return EF->LLVMFuzzerCustomMutator(Data, Size, MaxSize, Rand.Rand());
71}
72
73size_t MutationDispatcher::Mutate_CustomCrossOver(uint8_t *Data, size_t Size,
74                                                  size_t MaxSize) {
75  if (Size == 0)
76    return 0;
77  if (!CrossOverWith) return 0;
78  const Unit &Other = *CrossOverWith;
79  if (Other.empty())
80    return 0;
81  CustomCrossOverInPlaceHere.resize(MaxSize);
82  auto &U = CustomCrossOverInPlaceHere;
83  size_t NewSize = EF->LLVMFuzzerCustomCrossOver(
84      Data, Size, Other.data(), Other.size(), U.data(), U.size(), Rand.Rand());
85  if (!NewSize)
86    return 0;
87  assert(NewSize <= MaxSize && "CustomCrossOver returned overisized unit");
88  memcpy(Data, U.data(), NewSize);
89  return NewSize;
90}
91
92size_t MutationDispatcher::Mutate_ShuffleBytes(uint8_t *Data, size_t Size,
93                                               size_t MaxSize) {
94  if (Size > MaxSize || Size == 0) return 0;
95  size_t ShuffleAmount =
96      Rand(std::min(Size, (size_t)8)) + 1; // [1,8] and <= Size.
97  size_t ShuffleStart = Rand(Size - ShuffleAmount);
98  assert(ShuffleStart + ShuffleAmount <= Size);
99  std::shuffle(Data + ShuffleStart, Data + ShuffleStart + ShuffleAmount, Rand);
100  return Size;
101}
102
103size_t MutationDispatcher::Mutate_EraseBytes(uint8_t *Data, size_t Size,
104                                             size_t MaxSize) {
105  if (Size <= 1) return 0;
106  size_t N = Rand(Size / 2) + 1;
107  assert(N < Size);
108  size_t Idx = Rand(Size - N + 1);
109  // Erase Data[Idx:Idx+N].
110  memmove(Data + Idx, Data + Idx + N, Size - Idx - N);
111  // Printf("Erase: %zd %zd => %zd; Idx %zd\n", N, Size, Size - N, Idx);
112  return Size - N;
113}
114
115size_t MutationDispatcher::Mutate_InsertByte(uint8_t *Data, size_t Size,
116                                             size_t MaxSize) {
117  if (Size >= MaxSize) return 0;
118  size_t Idx = Rand(Size + 1);
119  // Insert new value at Data[Idx].
120  memmove(Data + Idx + 1, Data + Idx, Size - Idx);
121  Data[Idx] = RandCh(Rand);
122  return Size + 1;
123}
124
125size_t MutationDispatcher::Mutate_InsertRepeatedBytes(uint8_t *Data,
126                                                      size_t Size,
127                                                      size_t MaxSize) {
128  const size_t kMinBytesToInsert = 3;
129  if (Size + kMinBytesToInsert >= MaxSize) return 0;
130  size_t MaxBytesToInsert = std::min(MaxSize - Size, (size_t)128);
131  size_t N = Rand(MaxBytesToInsert - kMinBytesToInsert + 1) + kMinBytesToInsert;
132  assert(Size + N <= MaxSize && N);
133  size_t Idx = Rand(Size + 1);
134  // Insert new values at Data[Idx].
135  memmove(Data + Idx + N, Data + Idx, Size - Idx);
136  // Give preference to 0x00 and 0xff.
137  uint8_t Byte = Rand.RandBool() ? Rand(256) : (Rand.RandBool() ? 0 : 255);
138  for (size_t i = 0; i < N; i++)
139    Data[Idx + i] = Byte;
140  return Size + N;
141}
142
143size_t MutationDispatcher::Mutate_ChangeByte(uint8_t *Data, size_t Size,
144                                             size_t MaxSize) {
145  if (Size > MaxSize) return 0;
146  size_t Idx = Rand(Size);
147  Data[Idx] = RandCh(Rand);
148  return Size;
149}
150
151size_t MutationDispatcher::Mutate_ChangeBit(uint8_t *Data, size_t Size,
152                                            size_t MaxSize) {
153  if (Size > MaxSize) return 0;
154  size_t Idx = Rand(Size);
155  Data[Idx] ^= 1 << Rand(8);
156  return Size;
157}
158
159size_t MutationDispatcher::Mutate_AddWordFromManualDictionary(uint8_t *Data,
160                                                              size_t Size,
161                                                              size_t MaxSize) {
162  return AddWordFromDictionary(ManualDictionary, Data, Size, MaxSize);
163}
164
165size_t MutationDispatcher::ApplyDictionaryEntry(uint8_t *Data, size_t Size,
166                                                size_t MaxSize,
167                                                DictionaryEntry &DE) {
168  const Word &W = DE.GetW();
169  bool UsePositionHint = DE.HasPositionHint() &&
170                         DE.GetPositionHint() + W.size() < Size &&
171                         Rand.RandBool();
172  if (Rand.RandBool()) {  // Insert W.
173    if (Size + W.size() > MaxSize) return 0;
174    size_t Idx = UsePositionHint ? DE.GetPositionHint() : Rand(Size + 1);
175    memmove(Data + Idx + W.size(), Data + Idx, Size - Idx);
176    memcpy(Data + Idx, W.data(), W.size());
177    Size += W.size();
178  } else {  // Overwrite some bytes with W.
179    if (W.size() > Size) return 0;
180    size_t Idx = UsePositionHint ? DE.GetPositionHint() : Rand(Size - W.size());
181    memcpy(Data + Idx, W.data(), W.size());
182  }
183  return Size;
184}
185
186// Somewhere in the past we have observed a comparison instructions
187// with arguments Arg1 Arg2. This function tries to guess a dictionary
188// entry that will satisfy that comparison.
189// It first tries to find one of the arguments (possibly swapped) in the
190// input and if it succeeds it creates a DE with a position hint.
191// Otherwise it creates a DE with one of the arguments w/o a position hint.
192DictionaryEntry MutationDispatcher::MakeDictionaryEntryFromCMP(
193    const void *Arg1, const void *Arg2,
194    const void *Arg1Mutation, const void *Arg2Mutation,
195    size_t ArgSize, const uint8_t *Data,
196    size_t Size) {
197  bool HandleFirst = Rand.RandBool();
198  const void *ExistingBytes, *DesiredBytes;
199  Word W;
200  const uint8_t *End = Data + Size;
201  for (int Arg = 0; Arg < 2; Arg++) {
202    ExistingBytes = HandleFirst ? Arg1 : Arg2;
203    DesiredBytes = HandleFirst ? Arg2Mutation : Arg1Mutation;
204    HandleFirst = !HandleFirst;
205    W.Set(reinterpret_cast<const uint8_t*>(DesiredBytes), ArgSize);
206    const size_t kMaxNumPositions = 8;
207    size_t Positions[kMaxNumPositions];
208    size_t NumPositions = 0;
209    for (const uint8_t *Cur = Data;
210         Cur < End && NumPositions < kMaxNumPositions; Cur++) {
211      Cur =
212          (const uint8_t *)SearchMemory(Cur, End - Cur, ExistingBytes, ArgSize);
213      if (!Cur) break;
214      Positions[NumPositions++] = Cur - Data;
215    }
216    if (!NumPositions) continue;
217    return DictionaryEntry(W, Positions[Rand(NumPositions)]);
218  }
219  DictionaryEntry DE(W);
220  return DE;
221}
222
223
224template <class T>
225DictionaryEntry MutationDispatcher::MakeDictionaryEntryFromCMP(
226    T Arg1, T Arg2, const uint8_t *Data, size_t Size) {
227  if (Rand.RandBool()) Arg1 = Bswap(Arg1);
228  if (Rand.RandBool()) Arg2 = Bswap(Arg2);
229  T Arg1Mutation = Arg1 + Rand(-1, 1);
230  T Arg2Mutation = Arg2 + Rand(-1, 1);
231  return MakeDictionaryEntryFromCMP(&Arg1, &Arg2, &Arg1Mutation, &Arg2Mutation,
232                                    sizeof(Arg1), Data, Size);
233}
234
235DictionaryEntry MutationDispatcher::MakeDictionaryEntryFromCMP(
236    const Word &Arg1, const Word &Arg2, const uint8_t *Data, size_t Size) {
237  return MakeDictionaryEntryFromCMP(Arg1.data(), Arg2.data(), Arg1.data(),
238                                    Arg2.data(), Arg1.size(), Data, Size);
239}
240
241size_t MutationDispatcher::Mutate_AddWordFromTORC(
242    uint8_t *Data, size_t Size, size_t MaxSize) {
243  Word W;
244  DictionaryEntry DE;
245  switch (Rand(4)) {
246  case 0: {
247    auto X = TPC.TORC8.Get(Rand.Rand());
248    DE = MakeDictionaryEntryFromCMP(X.A, X.B, Data, Size);
249  } break;
250  case 1: {
251    auto X = TPC.TORC4.Get(Rand.Rand());
252    if ((X.A >> 16) == 0 && (X.B >> 16) == 0 && Rand.RandBool())
253      DE = MakeDictionaryEntryFromCMP((uint16_t)X.A, (uint16_t)X.B, Data, Size);
254    else
255      DE = MakeDictionaryEntryFromCMP(X.A, X.B, Data, Size);
256  } break;
257  case 2: {
258    auto X = TPC.TORCW.Get(Rand.Rand());
259    DE = MakeDictionaryEntryFromCMP(X.A, X.B, Data, Size);
260  } break;
261  case 3: if (Options.UseMemmem) {
262    auto X = TPC.MMT.Get(Rand.Rand());
263    DE = DictionaryEntry(X);
264  } break;
265  default:
266    assert(0);
267  }
268  if (!DE.GetW().size()) return 0;
269  Size = ApplyDictionaryEntry(Data, Size, MaxSize, DE);
270  if (!Size) return 0;
271  DictionaryEntry &DERef =
272      CmpDictionaryEntriesDeque[CmpDictionaryEntriesDequeIdx++ %
273                                kCmpDictionaryEntriesDequeSize];
274  DERef = DE;
275  CurrentDictionaryEntrySequence.push_back(&DERef);
276  return Size;
277}
278
279size_t MutationDispatcher::Mutate_AddWordFromPersistentAutoDictionary(
280    uint8_t *Data, size_t Size, size_t MaxSize) {
281  return AddWordFromDictionary(PersistentAutoDictionary, Data, Size, MaxSize);
282}
283
284size_t MutationDispatcher::AddWordFromDictionary(Dictionary &D, uint8_t *Data,
285                                                 size_t Size, size_t MaxSize) {
286  if (Size > MaxSize) return 0;
287  if (D.empty()) return 0;
288  DictionaryEntry &DE = D[Rand(D.size())];
289  Size = ApplyDictionaryEntry(Data, Size, MaxSize, DE);
290  if (!Size) return 0;
291  DE.IncUseCount();
292  CurrentDictionaryEntrySequence.push_back(&DE);
293  return Size;
294}
295
296// Overwrites part of To[0,ToSize) with a part of From[0,FromSize).
297// Returns ToSize.
298size_t MutationDispatcher::CopyPartOf(const uint8_t *From, size_t FromSize,
299                                      uint8_t *To, size_t ToSize) {
300  // Copy From[FromBeg, FromBeg + CopySize) into To[ToBeg, ToBeg + CopySize).
301  size_t ToBeg = Rand(ToSize);
302  size_t CopySize = Rand(ToSize - ToBeg) + 1;
303  assert(ToBeg + CopySize <= ToSize);
304  CopySize = std::min(CopySize, FromSize);
305  size_t FromBeg = Rand(FromSize - CopySize + 1);
306  assert(FromBeg + CopySize <= FromSize);
307  memmove(To + ToBeg, From + FromBeg, CopySize);
308  return ToSize;
309}
310
311// Inserts part of From[0,ToSize) into To.
312// Returns new size of To on success or 0 on failure.
313size_t MutationDispatcher::InsertPartOf(const uint8_t *From, size_t FromSize,
314                                        uint8_t *To, size_t ToSize,
315                                        size_t MaxToSize) {
316  if (ToSize >= MaxToSize) return 0;
317  size_t AvailableSpace = MaxToSize - ToSize;
318  size_t MaxCopySize = std::min(AvailableSpace, FromSize);
319  size_t CopySize = Rand(MaxCopySize) + 1;
320  size_t FromBeg = Rand(FromSize - CopySize + 1);
321  assert(FromBeg + CopySize <= FromSize);
322  size_t ToInsertPos = Rand(ToSize + 1);
323  assert(ToInsertPos + CopySize <= MaxToSize);
324  size_t TailSize = ToSize - ToInsertPos;
325  if (To == From) {
326    MutateInPlaceHere.resize(MaxToSize);
327    memcpy(MutateInPlaceHere.data(), From + FromBeg, CopySize);
328    memmove(To + ToInsertPos + CopySize, To + ToInsertPos, TailSize);
329    memmove(To + ToInsertPos, MutateInPlaceHere.data(), CopySize);
330  } else {
331    memmove(To + ToInsertPos + CopySize, To + ToInsertPos, TailSize);
332    memmove(To + ToInsertPos, From + FromBeg, CopySize);
333  }
334  return ToSize + CopySize;
335}
336
337size_t MutationDispatcher::Mutate_CopyPart(uint8_t *Data, size_t Size,
338                                           size_t MaxSize) {
339  if (Size > MaxSize || Size == 0) return 0;
340  // If Size == MaxSize, `InsertPartOf(...)` will
341  // fail so there's no point using it in this case.
342  if (Size == MaxSize || Rand.RandBool())
343    return CopyPartOf(Data, Size, Data, Size);
344  else
345    return InsertPartOf(Data, Size, Data, Size, MaxSize);
346}
347
348size_t MutationDispatcher::Mutate_ChangeASCIIInteger(uint8_t *Data, size_t Size,
349                                                     size_t MaxSize) {
350  if (Size > MaxSize) return 0;
351  size_t B = Rand(Size);
352  while (B < Size && !isdigit(Data[B])) B++;
353  if (B == Size) return 0;
354  size_t E = B;
355  while (E < Size && isdigit(Data[E])) E++;
356  assert(B < E);
357  // now we have digits in [B, E).
358  // strtol and friends don't accept non-zero-teminated data, parse it manually.
359  uint64_t Val = Data[B] - '0';
360  for (size_t i = B + 1; i < E; i++)
361    Val = Val * 10 + Data[i] - '0';
362
363  // Mutate the integer value.
364  switch(Rand(5)) {
365    case 0: Val++; break;
366    case 1: Val--; break;
367    case 2: Val /= 2; break;
368    case 3: Val *= 2; break;
369    case 4: Val = Rand(Val * Val); break;
370    default: assert(0);
371  }
372  // Just replace the bytes with the new ones, don't bother moving bytes.
373  for (size_t i = B; i < E; i++) {
374    size_t Idx = E + B - i - 1;
375    assert(Idx >= B && Idx < E);
376    Data[Idx] = (Val % 10) + '0';
377    Val /= 10;
378  }
379  return Size;
380}
381
382template<class T>
383size_t ChangeBinaryInteger(uint8_t *Data, size_t Size, Random &Rand) {
384  if (Size < sizeof(T)) return 0;
385  size_t Off = Rand(Size - sizeof(T) + 1);
386  assert(Off + sizeof(T) <= Size);
387  T Val;
388  if (Off < 64 && !Rand(4)) {
389    Val = Size;
390    if (Rand.RandBool())
391      Val = Bswap(Val);
392  } else {
393    memcpy(&Val, Data + Off, sizeof(Val));
394    T Add = Rand(21);
395    Add -= 10;
396    if (Rand.RandBool())
397      Val = Bswap(T(Bswap(Val) + Add)); // Add assuming different endiannes.
398    else
399      Val = Val + Add;               // Add assuming current endiannes.
400    if (Add == 0 || Rand.RandBool()) // Maybe negate.
401      Val = -Val;
402  }
403  memcpy(Data + Off, &Val, sizeof(Val));
404  return Size;
405}
406
407size_t MutationDispatcher::Mutate_ChangeBinaryInteger(uint8_t *Data,
408                                                      size_t Size,
409                                                      size_t MaxSize) {
410  if (Size > MaxSize) return 0;
411  switch (Rand(4)) {
412    case 3: return ChangeBinaryInteger<uint64_t>(Data, Size, Rand);
413    case 2: return ChangeBinaryInteger<uint32_t>(Data, Size, Rand);
414    case 1: return ChangeBinaryInteger<uint16_t>(Data, Size, Rand);
415    case 0: return ChangeBinaryInteger<uint8_t>(Data, Size, Rand);
416    default: assert(0);
417  }
418  return 0;
419}
420
421size_t MutationDispatcher::Mutate_CrossOver(uint8_t *Data, size_t Size,
422                                            size_t MaxSize) {
423  if (Size > MaxSize) return 0;
424  if (Size == 0) return 0;
425  if (!CrossOverWith) return 0;
426  const Unit &O = *CrossOverWith;
427  if (O.empty()) return 0;
428  MutateInPlaceHere.resize(MaxSize);
429  auto &U = MutateInPlaceHere;
430  size_t NewSize = 0;
431  switch(Rand(3)) {
432    case 0:
433      NewSize = CrossOver(Data, Size, O.data(), O.size(), U.data(), U.size());
434      break;
435    case 1:
436      NewSize = InsertPartOf(O.data(), O.size(), U.data(), U.size(), MaxSize);
437      if (!NewSize)
438        NewSize = CopyPartOf(O.data(), O.size(), U.data(), U.size());
439      break;
440    case 2:
441      NewSize = CopyPartOf(O.data(), O.size(), U.data(), U.size());
442      break;
443    default: assert(0);
444  }
445  assert(NewSize > 0 && "CrossOver returned empty unit");
446  assert(NewSize <= MaxSize && "CrossOver returned overisized unit");
447  memcpy(Data, U.data(), NewSize);
448  return NewSize;
449}
450
451void MutationDispatcher::StartMutationSequence() {
452  CurrentMutatorSequence.clear();
453  CurrentDictionaryEntrySequence.clear();
454}
455
456// Copy successful dictionary entries to PersistentAutoDictionary.
457void MutationDispatcher::RecordSuccessfulMutationSequence() {
458  for (auto DE : CurrentDictionaryEntrySequence) {
459    // PersistentAutoDictionary.AddWithSuccessCountOne(DE);
460    DE->IncSuccessCount();
461    assert(DE->GetW().size());
462    // Linear search is fine here as this happens seldom.
463    if (!PersistentAutoDictionary.ContainsWord(DE->GetW()))
464      PersistentAutoDictionary.push_back({DE->GetW(), 1});
465  }
466}
467
468void MutationDispatcher::PrintRecommendedDictionary() {
469  Vector<DictionaryEntry> V;
470  for (auto &DE : PersistentAutoDictionary)
471    if (!ManualDictionary.ContainsWord(DE.GetW()))
472      V.push_back(DE);
473  if (V.empty()) return;
474  Printf("###### Recommended dictionary. ######\n");
475  for (auto &DE: V) {
476    assert(DE.GetW().size());
477    Printf("\"");
478    PrintASCII(DE.GetW(), "\"");
479    Printf(" # Uses: %zd\n", DE.GetUseCount());
480  }
481  Printf("###### End of recommended dictionary. ######\n");
482}
483
484void MutationDispatcher::PrintMutationSequence() {
485  Printf("MS: %zd ", CurrentMutatorSequence.size());
486  for (auto M : CurrentMutatorSequence)
487    Printf("%s-", M.Name);
488  if (!CurrentDictionaryEntrySequence.empty()) {
489    Printf(" DE: ");
490    for (auto DE : CurrentDictionaryEntrySequence) {
491      Printf("\"");
492      PrintASCII(DE->GetW(), "\"-");
493    }
494  }
495}
496
497size_t MutationDispatcher::Mutate(uint8_t *Data, size_t Size, size_t MaxSize) {
498  return MutateImpl(Data, Size, MaxSize, Mutators);
499}
500
501size_t MutationDispatcher::DefaultMutate(uint8_t *Data, size_t Size,
502                                         size_t MaxSize) {
503  return MutateImpl(Data, Size, MaxSize, DefaultMutators);
504}
505
506// Mutates Data in place, returns new size.
507size_t MutationDispatcher::MutateImpl(uint8_t *Data, size_t Size,
508                                      size_t MaxSize,
509                                      Vector<Mutator> &Mutators) {
510  assert(MaxSize > 0);
511  // Some mutations may fail (e.g. can't insert more bytes if Size == MaxSize),
512  // in which case they will return 0.
513  // Try several times before returning un-mutated data.
514  for (int Iter = 0; Iter < 100; Iter++) {
515    auto M = Mutators[Rand(Mutators.size())];
516    size_t NewSize = (this->*(M.Fn))(Data, Size, MaxSize);
517    if (NewSize && NewSize <= MaxSize) {
518      if (Options.OnlyASCII)
519        ToASCII(Data, NewSize);
520      CurrentMutatorSequence.push_back(M);
521      return NewSize;
522    }
523  }
524  *Data = ' ';
525  return 1;   // Fallback, should not happen frequently.
526}
527
528// Mask represents the set of Data bytes that are worth mutating.
529size_t MutationDispatcher::MutateWithMask(uint8_t *Data, size_t Size,
530                                          size_t MaxSize,
531                                          const Vector<uint8_t> &Mask) {
532  size_t MaskedSize = std::min(Size, Mask.size());
533  // * Copy the worthy bytes into a temporary array T
534  // * Mutate T
535  // * Copy T back.
536  // This is totally unoptimized.
537  auto &T = MutateWithMaskTemp;
538  if (T.size() < Size)
539    T.resize(Size);
540  size_t OneBits = 0;
541  for (size_t I = 0; I < MaskedSize; I++)
542    if (Mask[I])
543      T[OneBits++] = Data[I];
544
545  if (!OneBits) return 0;
546  assert(!T.empty());
547  size_t NewSize = Mutate(T.data(), OneBits, OneBits);
548  assert(NewSize <= OneBits);
549  (void)NewSize;
550  // Even if NewSize < OneBits we still use all OneBits bytes.
551  for (size_t I = 0, J = 0; I < MaskedSize; I++)
552    if (Mask[I])
553      Data[I] = T[J++];
554  return Size;
555}
556
557void MutationDispatcher::AddWordToManualDictionary(const Word &W) {
558  ManualDictionary.push_back(
559      {W, std::numeric_limits<size_t>::max()});
560}
561
562}  // namespace fuzzer
563