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#include <fstream>
#include <iostream>
#include <sstream>
#include <wasmtime.hh>
using namespace wasmtime;
std::string readFile(const char *name) {
std::ifstream watFile;
watFile.open(name);
std::stringstream strStream;
strStream << watFile.rdbuf();
return strStream.str();
}
int main() {
// First the wasm module needs to be compiled. This is done with a global
// "compilation environment" within an `Engine`. Note that engines can be
// further configured through `Config` if desired instead of using the
// default like this is here.
std::cout << "Compiling module\n";
Engine engine;
auto module =
Module::compile(engine, readFile("examples/hello.wat")).unwrap();
// After a module is compiled we create a `Store` which will contain
// instantiated modules and other items like host functions. A Store
// contains an arbitrary piece of host information, and we use `MyState`
// here.
std::cout << "Initializing...\n";
Store store(engine);
// Our wasm module we'll be instantiating requires one imported function.
// the function takes no parameters and returns no results. We create a host
// implementation of that function here.
std::cout << "Creating callback...\n";
Func host_func =
Func::wrap(store, []() { std::cout << "Calling back...\n"; });
// Once we've got that all set up we can then move to the instantiation
// phase, pairing together a compiled module as well as a set of imports.
// Note that this is where the wasm `start` function, if any, would run.
std::cout << "Instantiating module...\n";
auto instance = Instance::create(store, module, {host_func}).unwrap();
// Next we poke around a bit to extract the `run` function from the module.
std::cout << "Extracting export...\n";
auto run = std::get<Func>(*instance.get(store, "run"));
// And last but not least we can call it!
std::cout << "Calling export...\n";
run.call(store, {}).unwrap();
std::cout << "Done\n";
}
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