fuzz compatibility with parity lib

.gitignore

@@ -1,3 +1,4 @@
 *.out
 *.test
 bin
+testdata/

compat/compat.go

@@ -0,0 +1,53 @@
+package compat
+
+/*
+#include <stdlib.h>
+#include "./rust/compat.h"
+#cgo LDFLAGS: ${SRCDIR}/rust/target/release/libcompat.a
+*/
+import "C"
+
+import (
+	"errors"
+	"unsafe"
+)
+
+//go:generate scalegen
+
+type Struct struct {
+	Field1 uint16
+	Field2 [3]byte
+}
+
+type Byte32 struct {
+	Array [32]byte
+}
+
+type Compat struct {
+	Field1  uint8
+	Field2  uint16
+	Field3  uint32
+	Field4  uint64
+	Field5  [8]byte
+	Field6  bool
+	Field7  *Struct
+	Field8  Struct
+	Field9  [4]Struct
+	Field10 []byte
+	Field11 []Byte32
+	Field12 [][]byte
+	Field13 []Struct
+}
+
+func RoundTrip(input []byte) ([]byte, error) {
+	ptr := C.CBytes(input)
+	defer C.free(ptr)
+	response := C.round_trip((*C.uchar)(ptr), C.size_t(len(input)))
+	defer C.free_response(response)
+	buf := make([]byte, response.len)
+	copy(buf, unsafe.Slice((*byte)(unsafe.Pointer(response.ptr)), response.len))
+	if response.code == 1 {
+		return nil, errors.New(string(buf))
+	}
+	return buf, nil
+}

compat/compat_test.go

@@ -0,0 +1,34 @@
+package compat
+
+import (
+	"bytes"
+	"testing"
+
+	fuzz "github.com/google/gofuzz"
+	"github.com/stretchr/testify/require"
+
+	"github.com/spacemeshos/go-scale"
+)
+
+func FuzzRoundTrip(f *testing.F) {
+	f.Add([]byte("0"))
+	f.Add([]byte("321321dssae12312asada3421"))
+	f.Fuzz(func(t *testing.T, data []byte) {
+		fuzzer := fuzz.NewFromGoFuzz(data)
+
+		compat := Compat{}
+		fuzzer.Fuzz(&compat)
+		buf := bytes.NewBuffer(nil)
+		_, err := compat.EncodeScale(scale.NewEncoder(buf))
+		require.NoError(t, err)
+
+		output, err := RoundTrip(buf.Bytes())
+		require.NoError(t, err)
+		require.Equal(t, buf.Bytes(), output)
+
+		result := Compat{}
+		_, err = result.DecodeScale(scale.NewDecoder(bytes.NewReader(output)))
+		require.NoError(t, err)
+		require.Equal(t, compat, result)
+	})
+}

compat/rust/.gitignore

@@ -0,0 +1,2 @@
+/target
+compat.h