From 7d5b7538f703ad5aff810a3ce1cc1e3f0fdc9e06 Mon Sep 17 00:00:00 2001
From: Andrei Maiboroda <andrei@ethereum.org>
Date: Tue, 15 Dec 2020 15:57:11 +0100
Subject: [PATCH] capi: Add function to clone a module

---
 include/fizzy/fizzy.h        | 11 +++++++++
 lib/fizzy/capi.cpp           | 13 +++++++++++
 test/unittests/capi_test.cpp | 43 ++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)

diff --git a/include/fizzy/fizzy.h b/include/fizzy/fizzy.h
index bbd723795..d6329dbe4 100644
--- a/include/fizzy/fizzy.h
+++ b/include/fizzy/fizzy.h
@@ -157,6 +157,17 @@ const FizzyModule* fizzy_parse(const uint8_t* wasm_binary, size_t wasm_binary_si
 /// If passed pointer is NULL, has no effect.
 void fizzy_free_module(const FizzyModule* module);
 
+/// Make a copy of a module.
+///
+/// @param  module    Pointer to module. Cannot be NULL.
+/// @returns          Pointer to a newly allocated module, identical to @a module, or NULL in case
+///                   memory for a module could not be allocated.
+///
+/// @note  Creating a copy is needed if more than single instance of a module is required, because
+/// instantiation takes ownership of a module, and the same module cannot be instantiated twice.
+/// @note  Input module is not modified neither in success nor in failure case.
+const FizzyModule* fizzy_clone_module(const FizzyModule* module);
+
 /// Get type of the function defined in the module.
 ///
 /// @param module   Pointer to module. Cannot be NULL.
diff --git a/lib/fizzy/capi.cpp b/lib/fizzy/capi.cpp
index 98f4c0db3..216d2444c 100644
--- a/lib/fizzy/capi.cpp
+++ b/lib/fizzy/capi.cpp
@@ -308,6 +308,19 @@ void fizzy_free_module(const FizzyModule* module)
     delete unwrap(module);
 }
 
+const FizzyModule* fizzy_clone_module(const FizzyModule* module)
+{
+    try
+    {
+        auto clone = std::make_unique<fizzy::Module>(*unwrap(module));
+        return wrap(clone.release());
+    }
+    catch (...)
+    {
+        return nullptr;
+    }
+}
+
 FizzyFunctionType fizzy_get_function_type(const FizzyModule* module, uint32_t func_idx)
 {
     return wrap(unwrap(module)->get_function_type(func_idx));
diff --git a/test/unittests/capi_test.cpp b/test/unittests/capi_test.cpp
index 53b713840..6b8c1a6d3 100644
--- a/test/unittests/capi_test.cpp
+++ b/test/unittests/capi_test.cpp
@@ -35,6 +35,29 @@ TEST(capi, free_module_null)
     fizzy_free_module(nullptr);
 }
 
+TEST(capi, clone_module)
+{
+    /* wat2wasm
+      (func (param i32 i32) (result i32) (i32.const 0))
+    */
+    const auto wasm = from_hex("0061736d0100000001070160027f7f017f030201000a0601040041000b");
+    const auto* module1 = fizzy_parse(wasm.data(), wasm.size());
+    EXPECT_NE(module1, nullptr);
+
+    const auto* module2 = fizzy_clone_module(module1);
+    EXPECT_NE(module2, nullptr);
+    EXPECT_NE(module1, module2);
+
+    const auto type2 = fizzy_get_function_type(module2, 0);
+    EXPECT_EQ(type2.output, FizzyValueTypeI32);
+    ASSERT_EQ(type2.inputs_size, 2);
+    EXPECT_EQ(type2.inputs[0], FizzyValueTypeI32);
+    EXPECT_EQ(type2.inputs[1], FizzyValueTypeI32);
+
+    fizzy_free_module(module2);
+    fizzy_free_module(module1);
+}
+
 TEST(capi, get_function_type)
 {
     /* wat2wasm
@@ -397,6 +420,26 @@ TEST(capi, instantiate_imported_globals)
         fizzy_instantiate(module, nullptr, 0, nullptr, nullptr, globals_type_mismatch, 4), nullptr);
 }
 
+TEST(capi, instantiate_twice)
+{
+    uint8_t wasm_prefix[]{0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00};
+    const auto* module1 = fizzy_parse(wasm_prefix, sizeof(wasm_prefix));
+    ASSERT_NE(module1, nullptr);
+
+    auto* instance1 = fizzy_instantiate(module1, nullptr, 0, nullptr, nullptr, nullptr, 0);
+    EXPECT_NE(instance1, nullptr);
+
+    const auto* module2 = fizzy_clone_module(module1);
+    ASSERT_NE(module2, nullptr);
+
+    auto* instance2 = fizzy_instantiate(module2, nullptr, 0, nullptr, nullptr, nullptr, 0);
+    EXPECT_NE(instance2, nullptr);
+    EXPECT_NE(instance1, instance2);
+
+    fizzy_free_instance(instance2);
+    fizzy_free_instance(instance1);
+}
+
 TEST(capi, resolve_instantiate_no_imports)
 {
     /* wat2wasm