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
16namespace fuzzer {
17
18// Cross Data1 and Data2, store the result (up to MaxOutSize bytes) in Out.
19size_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(a: OutSizeLeft, b: InSizeLeft);
37 size_t ExtraSize = Rand(MaxExtraSize) + 1;
38 memcpy(dest: Out + OutPos, src: Data + *InPos, n: 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
52

source code of compiler-rt/lib/fuzzer/FuzzerCrossOver.cpp