pre-filling fields

fuzz_test.go

@@ -33,3 +33,34 @@ func FuzzTest(f *testing.F) {
 		}
 	})
 }
+
+type MyStruct struct {
+	Field1 string
+	Field2 float32
+	Field3 int
+	Field4 [5]int
+}
+
+func FuzzTest2(f *testing.F) {
+	f.Fuzz(func(t *testing.T, genData []byte) {
+		if len(genData) < 15 {
+			return
+		}
+
+		fuzz2 := NewGenerator(genData)
+
+		fieldInfo := map[string]interface{}{
+			"MyStruct": MyStruct{Field1: "Value1", Field3: 100},
+		}
+		fuzz2.SetPreFilled(fieldInfo)
+
+		var newStruct MyStruct
+		err := fuzz2.GenerateStruct(&newStruct)
+
+		t.Log(newStruct.Field1)
+		t.Log(newStruct.Field2)
+
+		if err != nil {
+		}
+	})
+}

generator.go

@@ -14,16 +14,29 @@ type Generator struct {
 	position    uint32
 	mapStruct   map[string]interface{}
 	arrayStruct []interface{}
+	fieldInfo   map[string]interface{}
 }
 
 func NewGenerator(fuzzData []byte) *Generator {
 	return &Generator{
 		data:      fuzzData,
 		dataSize:  uint32(len(fuzzData)),
+		fieldInfo: make(map[string]interface{}),
 	}
 }
 
+func (g *Generator) SetPreFilled(fieldInfo map[string]interface{}) {
+	g.fieldInfo = fieldInfo
+}
+
 func (g *Generator) fillAny(any reflect.Value) error {
+
+	if fieldInfoValue, ok := g.fieldInfo[any.Type().String()]; ok {
+		fieldInfoData := reflect.ValueOf(fieldInfoValue)
+		any.Set(fieldInfoData)
+		return nil
+	}
+
 	switch any.Kind() {
 	case reflect.Struct:
 		for i := 0; i < any.NumField(); i++ {