mutator: Add custom cross over base functionality

Add custom cross over functionality in libFuzzer integration and mutator
framework APIs. Concrete cross over implementations are added later on.

3 files changed, 87 insertions, 0 deletions

diff --git a/src/test/java/com/code_intelligence/jazzer/mutation/ArgumentsMutatorTest.java b/src/test/java/com/code_intelligence/jazzer/mutation/ArgumentsMutatorTest.java
index 61579205..9a5bafd8 100644
--- a/src/test/java/com/code_intelligence/jazzer/mutation/ArgumentsMutatorTest.java
+++ b/src/test/java/com/code_intelligence/jazzer/mutation/ArgumentsMutatorTest.java
@@ -24,12 +24,15 @@ import static java.util.Collections.singletonList;
 import com.code_intelligence.jazzer.mutation.annotation.NotNull;
 import com.code_intelligence.jazzer.mutation.mutator.Mutators;
 import com.code_intelligence.jazzer.mutation.support.TestSupport.MockPseudoRandom;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Optional;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.parallel.ResourceLock;
 
+@SuppressWarnings("OptionalGetWithoutIsPresent")
 class ArgumentsMutatorTest {
   private static List<List<Boolean>> fuzzThisFunctionArgument1;
   private static List<Boolean> fuzzThisFunctionArgument2;
@@ -243,4 +246,53 @@ class ArgumentsMutatorTest {
     assertThat(mutableFuzzThisFunctionArgument1).containsExactly(singletonList(true));
     assertThat(mutableFuzzThisFunctionArgument2).containsExactly(false);
   }
+
+  @SuppressWarnings("unused")
+  public void crossOverFunction(List<Boolean> list) {}
+
+  @Test
+  @SuppressWarnings("unchecked")
+  void testCrossOver() throws Throwable {
+    Method method = ArgumentsMutatorTest.class.getMethod("crossOverFunction", List.class);
+    Optional<ArgumentsMutator> maybeMutator =
+        ArgumentsMutator.forInstanceMethod(Mutators.newFactory(), this, method);
+    assertThat(maybeMutator).isPresent();
+    ArgumentsMutator mutator = maybeMutator.get();
+
+    try (MockPseudoRandom prng = mockPseudoRandom(
+             // list not null
+             false,
+             // list size 1
+             1,
+             // not null,
+             false,
+             // boolean
+             true)) {
+      mutator.init(prng);
+    }
+    ByteArrayOutputStream baos1 = new ByteArrayOutputStream();
+    mutator.write(baos1);
+    byte[] out1 = baos1.toByteArray();
+
+    try (MockPseudoRandom prng = mockPseudoRandom(
+             // list not null
+             false,
+             // list size 1
+             1,
+             // not null
+             false,
+             // boolean
+             false)) {
+      mutator.init(prng);
+    }
+    ByteArrayOutputStream baos2 = new ByteArrayOutputStream();
+    mutator.write(baos2);
+    byte[] out2 = baos1.toByteArray();
+
+    mutator.crossOver(new ByteArrayInputStream(out1), new ByteArrayInputStream(out2), 12345);
+    Object[] arguments = mutator.getArguments();
+
+    assertThat(arguments).isNotEmpty();
+    assertThat((List<Boolean>) arguments[0]).isNotEmpty();
+  }
 }
diff --git a/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java b/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
index a8424ecb..ccf893d2 100644
--- a/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
+++ b/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
@@ -79,6 +79,10 @@ class MutatorCombinatorsTest {
       }
 
       @Override
+      public void crossOverInPlace(
+          List<Integer> reference, List<Integer> otherReference, PseudoRandom prng) {}
+
+      @Override
       public String toDebugString(Predicate<Debuggable> isInCycle) {
         return "List<Integer>";
       }
@@ -122,6 +126,10 @@ class MutatorCombinatorsTest {
           }
 
           @Override
+          public void crossOverInPlace(
+              List<Integer> reference, List<Integer> otherReference, PseudoRandom prng) {}
+
+          @Override
           public String toDebugString(Predicate<Debuggable> isInCycle) {
             return "List<Integer>";
           }
diff --git a/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java b/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
index 9a39f186..d4e15a78 100644
--- a/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
+++ b/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
@@ -136,6 +136,11 @@ public final class TestSupport {
     }
 
     @Override
+    public T crossOver(T value, T otherValue, PseudoRandom prng) {
+      return value;
+    }
+
+    @Override
     public String toDebugString(Predicate<Debuggable> isInCycle) {
       T initialValue = nextInitialValue();
       if (initialValue == null) {
@@ -301,6 +306,28 @@ public final class TestSupport {
     }
 
     @Override
+    public <T> T pickValue(
+        T value, T otherValue, Supplier<T> supplier, int inverseSupplierFrequency) {
+      assertThat(elements).isNotEmpty();
+      switch ((int) elements.poll()) {
+        case 0:
+          return value;
+        case 1:
+          return otherValue;
+        case 2:
+          return producer.get();
+        default:
+          throw new AssertionError("Invalid pickValue element");
+      }
+    }
+
+    @Override
+    public long nextLong() {
+      assertThat(elements).isNotEmpty();
+      return (long) elements.poll();
+    }
+
+    @Override
     public void close() {
       assertThat(elements).isEmpty();
     }