C API instantiate with resolving imported functions

include/fizzy/fizzy.h

@@ -80,6 +80,17 @@ typedef struct FizzyExternalFunction
     void* context;
 } FizzyExternalFunction;
 
+/// Imported function.
+typedef struct FizzyImportedFunction
+{
+    /// Module name. NULL-terminated string. Cannot be NULL.
+    const char* module;
+    /// Function name. NULL-terminated string. Cannot be NULL.
+    const char* name;
+    /// External function, defining its type, pointer to function and context for calling it.
+    FizzyExternalFunction external_function;
+} FizzyImportedFunction;
+
 /// Validate binary module.
 bool fizzy_validate(const uint8_t* wasm_binary, size_t wasm_binary_size);
 
@@ -130,6 +141,22 @@ bool fizzy_find_exported_function(
 FizzyInstance* fizzy_instantiate(const FizzyModule* module,
     const FizzyExternalFunction* imported_functions, size_t imported_functions_size);
 
+/// Instantiate a module resolving imported functions.
+/// Takes ownership of module, i.e. @p module is invalidated after this call.
+///
+/// @param      module                   Pointer to module.
+/// @param      imported_functions       Pointer to the imported function array. Can be NULL iff
+///                                      imported_functions_size equals 0.
+/// @param      imported_functions_size  Size of the imported function array. Can be zero.
+/// @returns    non-NULL pointer to instance in case of success, NULL otherwise.
+///
+/// @note
+/// Functions in @a imported_functions are allowed to be in any order and allowed to include some
+/// functions not required by the module.
+/// Functions are matched to module's imports based on their module and name strings.
+FizzyInstance* fizzy_resolve_instantiate(const FizzyModule* module,
+    const FizzyImportedFunction* imported_functions, size_t imported_functions_size);
+
 /// Free resources associated with the instance.
 /// If passed pointer is NULL, has no effect.
 void fizzy_free_instance(FizzyInstance* instance);

lib/fizzy/capi.cpp

@@ -115,6 +115,28 @@ inline fizzy::ExternalFunction unwrap(const FizzyExternalFunction& external_func
     return fizzy::ExternalFunction{
         unwrap(external_func.function, external_func.context), unwrap(external_func.type)};
 }
+
+inline fizzy::ImportedFunction unwrap(const FizzyImportedFunction& c_imported_func)
+{
+    fizzy::ImportedFunction imported_func;
+    imported_func.module =
+        c_imported_func.module ? std::string{c_imported_func.module} : std::string{};
+    imported_func.name = c_imported_func.name ? std::string{c_imported_func.name} : std::string{};
+
+    const auto& c_type = c_imported_func.external_function.type;
+    fizzy::ValType (*unwrap_valtype_fn)(FizzyValueType value) = &unwrap;
+    std::transform(c_type.inputs, c_type.inputs + c_type.inputs_size, imported_func.inputs.begin(),
+        unwrap_valtype_fn);
+    imported_func.output = c_type.output == FizzyValueTypeVoid ?
+                               std::nullopt :
+                               std::make_optional(unwrap(c_type.output));
+
+    imported_func.function = unwrap(
+        c_imported_func.external_function.function, c_imported_func.external_function.context);
+
+    return imported_func;
+}
+
 }  // namespace
 
 extern "C" {
@@ -186,6 +208,29 @@ FizzyInstance* fizzy_instantiate(const FizzyModule* module,
     }
 }
 
+FizzyInstance* fizzy_resolve_instantiate(const FizzyModule* c_module,
+    const FizzyImportedFunction* c_imported_functions, size_t imported_functions_size)
+{
+    try
+    {
+        std::vector<fizzy::ImportedFunction> imported_functions(imported_functions_size);
+        fizzy::ImportedFunction (*unwrap_imported_func_fn)(const FizzyImportedFunction&) = &unwrap;
+        std::transform(c_imported_functions, c_imported_functions + imported_functions_size,
+            imported_functions.begin(), unwrap_imported_func_fn);
+
+        std::unique_ptr<const fizzy::Module> module{unwrap(c_module)};
+        auto resolved_imports = fizzy::resolve_imported_functions(*module, imported_functions);
+
+        auto instance = fizzy::instantiate(std::move(module), std::move(resolved_imports));
+
+        return wrap(instance.release());
+    }
+    catch (...)
+    {
+        return nullptr;
+    }
+}
+
 void fizzy_free_instance(FizzyInstance* instance)
 {
     delete unwrap(instance);

test/unittests/capi_test.cpp

@@ -136,6 +136,99 @@ TEST(capi, instantiate_imported_function)
     fizzy_free_instance(instance);
 }
 
+TEST(capi, resolve_instantiate_no_imports)
+{
+    /* wat2wasm
+      (module)
+    */
+    const auto wasm = from_hex("0061736d01000000");
+    auto module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+
+    auto instance = fizzy_resolve_instantiate(module, nullptr, 0);
+    EXPECT_NE(instance, nullptr);
+
+    fizzy_free_instance(instance);
+
+    module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+
+    FizzyImportedFunction host_funcs[] = {{"mod", "foo",
+        {{FizzyValueTypeVoid, nullptr, 0},
+            [](void*, FizzyInstance*, const FizzyValue*, int) { return FizzyExecutionResult{}; },
+            nullptr}}};
+
+    instance = fizzy_resolve_instantiate(module, host_funcs, 1);
+    EXPECT_NE(instance, nullptr);
+
+    fizzy_free_instance(instance);
+}
+
+TEST(capi, resolve_instantiate)
+{
+    /* wat2wasm
+      (func (import "mod1" "foo1") (result i32))
+      (func (import "mod1" "foo2") (result i64))
+      (func (import "mod2" "foo1") (result f32))
+      (func (import "mod2" "foo2") (result f64))
+    */
+    const auto wasm = from_hex(
+        "0061736d010000000111046000017f6000017e6000017d6000017c023104046d6f643104666f6f310000046d6f"
+        "643104666f6f320001046d6f643204666f6f310002046d6f643204666f6f320003");
+    auto module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+
+    EXPECT_EQ(fizzy_instantiate(module, nullptr, 0), nullptr);
+
+    module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+
+    FizzyExternalFn host_fn = [](void* context, FizzyInstance*, const FizzyValue*, int) {
+        return FizzyExecutionResult{true, false, *static_cast<FizzyValue*>(context)};
+    };
+
+    FizzyValue result_int{42};
+    FizzyExternalFunction mod1foo1 = {{FizzyValueTypeI32, nullptr, 0}, host_fn, &result_int};
+    FizzyExternalFunction mod1foo2 = {{FizzyValueTypeI64, nullptr, 0}, host_fn, &result_int};
+    FizzyValue result_f32;
+    result_f32.f32 = 42;
+    FizzyExternalFunction mod2foo1 = {{FizzyValueTypeF32, nullptr, 0}, host_fn, &result_f32};
+    FizzyValue result_f64;
+    result_f64.f64 = 42;
+    FizzyExternalFunction mod2foo2 = {{FizzyValueTypeF64, nullptr, 0}, host_fn, &result_f64};
+
+    FizzyImportedFunction host_funcs[] = {{"mod1", "foo1", mod1foo1}, {"mod1", "foo2", mod1foo2},
+        {"mod2", "foo1", mod2foo1}, {"mod2", "foo2", mod2foo2}};
+
+    auto instance = fizzy_resolve_instantiate(module, host_funcs, 4);
+    EXPECT_NE(instance, nullptr);
+    fizzy_free_instance(instance);
+
+    // reordered functions
+    module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+    FizzyImportedFunction host_funcs_reordered[] = {{"mod1", "foo2", mod1foo2},
+        {"mod2", "foo1", mod2foo1}, {"mod2", "foo2", mod2foo2}, {"mod1", "foo1", mod1foo1}};
+    instance = fizzy_resolve_instantiate(module, host_funcs_reordered, 4);
+    EXPECT_NE(instance, nullptr);
+    fizzy_free_instance(instance);
+
+    // extra functions
+    module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+    FizzyImportedFunction host_funcs_extra[] = {{"mod1", "foo1", mod1foo1},
+        {"mod1", "foo2", mod1foo2}, {"mod2", "foo1", mod2foo1}, {"mod2", "foo2", mod2foo2},
+        {"mod3", "foo1", mod1foo1}};
+    instance = fizzy_resolve_instantiate(module, host_funcs_extra, 4);
+    EXPECT_NE(instance, nullptr);
+    fizzy_free_instance(instance);
+
+    // not enough functions
+    module = fizzy_parse(wasm.data(), wasm.size());
+    ASSERT_NE(module, nullptr);
+    EXPECT_EQ(fizzy_resolve_instantiate(module, host_funcs, 3), nullptr);
+}
+
 TEST(capi, free_instance_null)
 {
     fizzy_free_instance(nullptr);