VmtHook: Add easy API for hooking methods

include/safetyhook/easy.hpp

@@ -38,4 +38,12 @@ namespace safetyhook {
 }
 
 [[nodiscard]] VmtHook create_vmt(void* object);
+[[nodiscard]] VmHook create_vm(VmtHook& vmt, size_t index, FnPtr auto destination) {
+    if (auto hook = vmt.hook_method(index, destination)) {
+        return std::move(*hook);
+    } else {
+        return {};
+    }
+}
+
 } // namespace safetyhook

unittest/vmt_hook.cpp

@@ -297,4 +297,35 @@ TEST_CASE("Can remove an object that was previously VMT hooked", "[vmt_hook]") {
     REQUIRE(target0->add_42(2) == 44);
     REQUIRE(target1->add_42(2) == 44);
     REQUIRE(target2->add_42(2) == 44);
-}
+}
+
+TEST_CASE("VMT hook an object instance with easy API", "[vmt_hook]") {
+    struct Interface {
+        virtual ~Interface() = default;
+        virtual int add_42(int a) = 0;
+    };
+
+    struct Target : Interface {
+        __declspec(noinline) int add_42(int a) override { return a + 42; }
+    };
+
+    std::unique_ptr<Interface> target = std::make_unique<Target>();
+
+    REQUIRE(target->add_42(0) == 42);
+
+    static SafetyHookVmt target_hook{};
+    static SafetyHookVm add_42_hook{};
+
+    struct Hook : Target {
+        int hooked_add_42(int a) { return add_42_hook.thiscall<int>(this, a) + 1337; }
+    };
+
+    target_hook = safetyhook::create_vmt(target.get());
+    add_42_hook = safetyhook::create_vm(target_hook, 1, &Hook::hooked_add_42);
+
+    REQUIRE(target->add_42(1) == 1380);
+
+    add_42_hook.reset();
+
+    REQUIRE(target->add_42(2) == 44);
+}