compiler-rt/lib/fuzzer/FuzzerCrossOver.cpp

   1 //===- FuzzerCrossOver.cpp - Cross over two test inputs -------------------===//
   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 // Cross over test inputs.
   9 //===----------------------------------------------------------------------===//
  10
  11 #include "FuzzerDefs.h"
  12 #include "FuzzerMutate.h"
  13 #include "FuzzerRandom.h"
  14 #include <cstring>
  15
  16 namespace fuzzer {
  17
  18 // Cross Data1 and Data2, store the result (up to MaxOutSize bytes) in Out.
  19 size_t MutationDispatcher::CrossOver(const uint8_t *Data1, size_t Size1,
  20                                      const uint8_t *Data2, size_t Size2,
  21                                      uint8_t *Out, size_t MaxOutSize) {
  22   assert(Size1 || Size2);
  23   MaxOutSize = Rand(MaxOutSize) + 1;
  24   size_t OutPos = 0;
  25   size_t Pos1 = 0;
  26   size_t Pos2 = 0;
  27   size_t *InPos = &Pos1;
  28   size_t InSize = Size1;
  29   const uint8_t *Data = Data1;
  30   bool CurrentlyUsingFirstData = true;
  31   while (OutPos < MaxOutSize && (Pos1 < Size1 || Pos2 < Size2)) {
  32     // Merge a part of Data into Out.
  33     size_t OutSizeLeft = MaxOutSize - OutPos;
  34     if (*InPos < InSize) {
  35       size_t InSizeLeft = InSize - *InPos;
  36       size_t MaxExtraSize = std::min(OutSizeLeft, InSizeLeft);
  37       size_t ExtraSize = Rand(MaxExtraSize) + 1;
  38       memcpy(Out + OutPos, Data + *InPos, ExtraSize);
  39       OutPos += ExtraSize;
  40       (*InPos) += ExtraSize;
  41     }
  42     // Use the other input data on the next iteration.
  43     InPos  = CurrentlyUsingFirstData ? &Pos2 : &Pos1;
  44     InSize = CurrentlyUsingFirstData ? Size2 : Size1;
  45     Data   = CurrentlyUsingFirstData ? Data2 : Data1;
  46     CurrentlyUsingFirstData = !CurrentlyUsingFirstData;
  47   }
  48   return OutPos;
  49 }
  50
  51 }  // namespace fuzzer