1 /*
2 Example of instantiating of the WebAssembly module and invoking its exported
3 function.
4
5 You can build the example using CMake:
6
7 mkdir build && (cd build && cmake .. && \
8 cmake --build . --target wasmtime-multi-cpp)
9
10 And then run it:
11
12 build/wasmtime-multi-cpp
13 */
14
15 #include <fstream>
16 #include <iostream>
17 #include <sstream>
18 #include <wasmtime.hh>
19
20 using namespace wasmtime;
21
readFile(const char * name)22 std::string readFile(const char *name) {
23 std::ifstream watFile;
24 watFile.open(name);
25 std::stringstream strStream;
26 strStream << watFile.rdbuf();
27 return strStream.str();
28 }
29
main()30 int main() {
31 std::cout << "Initializing...\n";
32 Engine engine;
33 Store store(engine);
34
35 std::cout << "Compiling module...\n";
36 auto wat = readFile("examples/multi.wat");
37 Module module = Module::compile(engine, wat).unwrap();
38
39 std::cout << "Creating callback...\n";
40 Func callback_func = Func::wrap(
41 store, [](int32_t a, int64_t b) -> std::tuple<int64_t, int32_t> {
42 // Rust example adds 1 to each argument but flips order.
43 return std::make_tuple(b + 1, a + 1);
44 });
45
46 std::cout << "Instantiating module...\n";
47 Instance instance = Instance::create(store, module, {callback_func}).unwrap();
48
49 std::cout << "Extracting export...\n";
50 Func g = std::get<Func>(*instance.get(store, "g"));
51
52 std::cout << "Calling export \"g\"...\n";
53 // Provide (i32=1, i64=3) like the Rust example
54 auto results = g.call(store, {Val(int32_t(1)), Val(int64_t(3))}).unwrap();
55
56 std::cout << "Printing result...\n";
57 std::cout << "> " << results[0].i64() << " " << results[1].i32() << "\n";
58
59 std::cout << "Calling export \"round_trip_many\"...\n";
60 Func round_trip_many =
61 std::get<Func>(*instance.get(store, "round_trip_many"));
62 auto many_results =
63 round_trip_many
64 .call(store, {Val(int64_t(0)), Val(int64_t(1)), Val(int64_t(2)),
65 Val(int64_t(3)), Val(int64_t(4)), Val(int64_t(5)),
66 Val(int64_t(6)), Val(int64_t(7)), Val(int64_t(8)),
67 Val(int64_t(9))})
68 .unwrap();
69 std::cout << "Printing result...\n";
70 std::cout << "> (";
71 for (size_t i = 0; i < many_results.size(); i++) {
72 if (i)
73 std::cout << ", ";
74 std::cout << many_results[i].i64();
75 }
76 std::cout << ")\n";
77 return 0;
78 }
79