vendor/llvm/llvm-trunk-r238337

1 files changed, 71 insertions, 0 deletions

diff --git a/lib/Fuzzer/FuzzerMutate.cpp b/lib/Fuzzer/FuzzerMutate.cpp
new file mode 100644
index 0000000000000..f537fa90fd850
--- /dev/null
+++ b/lib/Fuzzer/FuzzerMutate.cpp
@@ -0,0 +1,71 @@
+//===- 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) {
+  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() {
+  if (rand() % 2) return rand();
+  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) {
+  assert(MaxSize > 0);
+  assert(Size <= MaxSize);
+  if (Size == 0) {
+    for (size_t i = 0; i < MaxSize; i++)
+      Data[i] = RandCh();
+    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();
+    }
+    Data[Idx] = RandCh();
+    break;
+  case 2:
+    Data[Idx] = FlipRandomBit(Data[Idx]);
+    break;
+  }
+  assert(Size > 0);
+  return Size;
+}
+
+}  // namespace fuzzer