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//===- FuzzerMutate.cpp - Mutate a test input -----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Mutate a test input.
//===----------------------------------------------------------------------===//
#include <cstring>
#include "FuzzerInternal.h"
namespace fuzzer {
static char FlipRandomBit(char X, FuzzerRandomBase &Rand) {
int Bit = Rand(8);
char Mask = 1 << Bit;
char R;
if (X & (1 << Bit))
R = X & ~Mask;
else
R = X | Mask;
assert(R != X);
return R;
}
static char RandCh(FuzzerRandomBase &Rand) {
if (Rand.RandBool()) return Rand(256);
const char *Special = "!*'();:@&=+$,/?%#[]123ABCxyz-`~.";
return Special[Rand(sizeof(Special) - 1)];
}
// Mutates Data in place, returns new size.
size_t Mutate(uint8_t *Data, size_t Size, size_t MaxSize,
FuzzerRandomBase &Rand) {
assert(MaxSize > 0);
assert(Size <= MaxSize);
if (Size == 0) {
for (size_t i = 0; i < MaxSize; i++)
Data[i] = RandCh(Rand);
return MaxSize;
}
assert(Size > 0);
size_t Idx = Rand(Size);
switch (Rand(3)) {
case 0:
if (Size > 1) {
// Erase Data[Idx].
memmove(Data + Idx, Data + Idx + 1, Size - Idx - 1);
Size = Size - 1;
}
[[clang::fallthrough]];
case 1:
if (Size < MaxSize) {
// Insert new value at Data[Idx].
memmove(Data + Idx + 1, Data + Idx, Size - Idx);
Data[Idx] = RandCh(Rand);
}
Data[Idx] = RandCh(Rand);
break;
case 2:
Data[Idx] = FlipRandomBit(Data[Idx], Rand);
break;
}
assert(Size > 0);
return Size;
}
} // namespace fuzzer
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