🚧 Add an empty watermarking function

example/test2.wast

+(module
+    (export "f1" (func $f1))
+    (export "f2" (func $f2))
+    (export "f3" (func $f3))
+    (func $f1 (result i32)
+        (i32.add
+            (i32.const 1)
+            (i32.const 2)
+        )
+    )
+    (func $f2 (result i32)
+        (i32.add
+            (i32.add
+                (i32.const 1)
+                (i32.const 2)
+            )
+            (i32.const 3)
+        )
+    )
+    (func $f3 (result i32)
+        (i32.add
+            (i32.add
+                (i32.const 1)
+                (i32.const 2)
+            )
+            (i32.add
+                (i32.const 4)
+                (i32.const 3)
+            )
+        )
+    )
+)

src/CMakeLists.txt

 add_library(kyut
     kyut/watermarker/FunctionOrderingWatermarker.cpp
+    kyut/watermarker/OperandSwappingWatermarker.cpp
 )
 
 target_link_libraries(kyut

src/kyut/watermarker/OperandSwappingWatermarker.cpp

+#include "OperandSwappingWatermarker.hpp"
+
+namespace kyut::watermarker {
+
+    std::size_t embedOperandSwapping(wasm::Module &module, CircularBitStreamReader &stream) {
+        (void)module;
+        (void)stream;
+        return 0;
+    }
+
+    std::size_t extractOperandSwapping(wasm::Module &module, BitStreamWriter &stream) {
+        (void)module;
+        (void)stream;
+        return 0;
+    }
+} // namespace kyut::watermarker

src/kyut/watermarker/OperandSwappingWatermarker.hpp

+#ifndef INCLUDE_kyut_watermark_OperandSwappingWatermarker_hpp
+#define INCLUDE_kyut_watermark_OperandSwappingWatermarker_hpp
+
+#include <wasm.h>
+
+namespace kyut {
+    class BitStreamWriter;
+    class CircularBitStreamReader;
+} // namespace kyut
+
+namespace kyut::watermarker {
+    /**
+     * @brief   Embed watermarks by operand swapping.
+     *
+     * @param   module          A reference to the WebAssembly module in which watermarks will be embedded.
+     * @param   stream          Input stream containing watermarks to embed.
+     * @return  Number of watermark bits embedded in the module.
+     */
+    std::size_t embedOperandSwapping(wasm::Module &module, CircularBitStreamReader &stream);
+
+    /**
+     * @brief Extract watermarks by operand swapping.
+     *
+     * @param   module          A reference to the WebAssembly module with embedded watermarks.
+     * @param   stream          Output stream to save the watermarks.
+     * @return  Number of watermark bits extracted from the module.
+     */
+    std::size_t extractOperandSwapping(wasm::Module &module, BitStreamWriter &stream);
+} // namespace kyut::watermarker
+
+#endif // INCLUDE_kyut_watermark_OperandSwappingWatermarker_hpp

test/CMakeLists.txt

@@ -3,6 +3,7 @@ add_executable(test_kyut
     kyut/test_CircularBitStreamReader.cpp
     kyut/test_BitStreamWriter.cpp
     kyut/watermarker/test_FunctionOrderingWatermarker.cpp
+    kyut/watermarker/test_OperandSwappingWatermarker.cpp
 )
 
 target_compile_definitions(test_kyut

test/kyut/watermarker/test_OperandSwappingWatermarker.cpp

+#include <kyut/watermarker/OperandSwappingWatermarker.hpp>
+
+#include <boost/test/unit_test.hpp>
+
+#include <wasm-io.h>
+
+#include <kyut/BitStreamWriter.hpp>
+#include <kyut/CircularBitStreamReader.hpp>
+
+#ifndef KYUT_TEST_SOURCE_DIR
+#define KYUT_TEST_SOURCE_DIR "."
+#endif
+
+BOOST_AUTO_TEST_SUITE(kyut)
+BOOST_AUTO_TEST_SUITE(watermarker)
+
+BOOST_AUTO_TEST_CASE(embed_operand_swapping) {
+    wasm::Module module;
+    wasm::ModuleReader{}.read(KYUT_TEST_SOURCE_DIR "/example/test2.wast", module);
+
+    BOOST_REQUIRE_EQUAL(module.functions.size(), std::size_t{3});
+    BOOST_REQUIRE_EQUAL(module.functions[0]->name, "f1");
+    BOOST_REQUIRE_EQUAL(module.functions[1]->name, "f2");
+    BOOST_REQUIRE_EQUAL(module.functions[2]->name, "f3");
+
+    // Embed 0b0000'00
+    {
+        CircularBitStreamReader s{{0b0000'0000}};
+        const auto numBitsEmbedded = embedOperandSwapping(module, s);
+
+        BOOST_REQUIRE_EQUAL(numBitsEmbedded, std::size_t{6});
+        BOOST_REQUIRE_EQUAL(module.functions.size(), std::size_t{3});
+        BOOST_REQUIRE_EQUAL(module.functions[0]->name, "f1");
+        BOOST_REQUIRE_EQUAL(module.functions[1]->name, "f2");
+        BOOST_REQUIRE_EQUAL(module.functions[2]->name, "f3");
+
+        // f1
+        {
+            const auto bin = module.functions[0]->body->cast<wasm::Binary>();
+
+            BOOST_REQUIRE_EQUAL(bin->left->cast<wasm::Const>()->value.geti32(), 1);
+            BOOST_REQUIRE_EQUAL(bin->right->cast<wasm::Const>()->value.geti32(), 2);
+        }
+    }
+}
+
+BOOST_AUTO_TEST_SUITE_END() BOOST_AUTO_TEST_SUITE_END()