FuzzerCrossOver.cpp

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//===- FuzzerCrossOver.cpp - Cross over two test inputs -------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

// Cross over test inputs.

//===----------------------------------------------------------------------===//

#include "FuzzerDefs.h"

#include "FuzzerMutate.h"

#include "FuzzerRandom.h"

#include <cstring>

namespace fuzzer {

// Cross Data1 and Data2, store the result (up to MaxOutSize bytes) in Out.

size_t MutationDispatcher::CrossOver(const uint8_t *Data1, size_t Size1,

                                     const uint8_t *Data2, size_t Size2,

                                     uint8_t *Out, size_t MaxOutSize) {

  assert(Size1 || Size2);

  MaxOutSize = Rand(MaxOutSize) + 1;

  size_t OutPos = 0;

  size_t Pos1 = 0;

  size_t Pos2 = 0;

  size_t *InPos = &Pos1;

  size_t InSize = Size1;

  const uint8_t *Data = Data1;

  bool CurrentlyUsingFirstData = true;

  while (OutPos < MaxOutSize && (Pos1 < Size1 || Pos2 < Size2)) {

    // Merge a part of Data into Out.

    size_t OutSizeLeft = MaxOutSize - OutPos;

    if (*InPos < InSize) {

      size_t InSizeLeft = InSize - *InPos;

      size_t MaxExtraSize = std::min(OutSizeLeft, InSizeLeft);

      size_t ExtraSize = Rand(MaxExtraSize) + 1;

      memcpy(Out + OutPos, Data + *InPos, ExtraSize);

      OutPos += ExtraSize;

      (*InPos) += ExtraSize;

    // Use the other input data on the next iteration.

    InPos  = CurrentlyUsingFirstData ? &Pos2 : &Pos1;

    InSize = CurrentlyUsingFirstData ? Size2 : Size1;

    Data   = CurrentlyUsingFirstData ? Data2 : Data1;

    CurrentlyUsingFirstData = !CurrentlyUsingFirstData;

  return OutPos;

}  // namespace fuzzer