wasmer/lib/c-api/examples/instance.c

#include <stdio.h>
#include "wasmer.h"

int main(int argc, const char* argv[]) {
    const char *wat_string =
        "(module\n"
        "  (type $add_one_t (func (param i32) (result i32)))\n"
        "  (func $add_one_f (type $add_one_t) (param $value i32) (result i32)\n"
        "    local.get $value\n"
        "    i32.const 1\n"
        "    i32.add)\n"
        "  (export \"add_one\" (func $add_one_f)))";

    wasm_byte_vec_t wat;
    wasm_byte_vec_new(&wat, strlen(wat_string), wat_string);
    wasm_byte_vec_t wasm_bytes;
    wat2wasm(&wat, &wasm_bytes);
    wasm_byte_vec_delete(&wat);

    printf("Creating the store...\n");
    wasm_engine_t* engine = wasm_engine_new();
    wasm_store_t* store = wasm_store_new(engine);

    printf("Compiling module...\n");
    wasm_module_t* module = wasm_module_new(store, &wasm_bytes);

    if (!module) {
        printf("> Error compiling module!\n");

        return 1;
    }

    wasm_byte_vec_delete(&wasm_bytes);

    printf("Creating imports...\n");
    wasm_extern_vec_t imports = WASM_EMPTY_VEC;

    printf("Instantiating module...\n");
    wasm_instance_t* instance = wasm_instance_new(store, module, &imports, NULL);

    if (!instance) {
      printf("> Error instantiating module!\n");

      return 1;
    }

    printf("Retrieving exports...\n");
    wasm_extern_vec_t exports;
    wasm_instance_exports(instance, &exports);

    if (exports.size == 0) {
        printf("> Error accessing exports!\n");

        return 1;
    }

    const wasm_func_t* add_one_func = wasm_extern_as_func(exports.data[0]);
    if (add_one_func == NULL) {
        printf("> Error accessing export!\n");

        return 1;
    }

    wasm_module_delete(module);
    wasm_instance_delete(instance);

    printf("Calling `add_one` function...\n");
    wasm_val_t args_val[1] = { WASM_I32_VAL(1) };
    wasm_val_t results_val[1] = { WASM_INIT_VAL };
    wasm_val_vec_t args = WASM_ARRAY_VEC(args_val);
    wasm_val_vec_t results = WASM_ARRAY_VEC(results_val);

    if (wasm_func_call(add_one_func, &args, &results)) {
        printf("> Error calling function!\n");

        return 1;
    }

    printf("Results of `add_one`: %d\n", results_val[0].of.i32);

    wasm_extern_vec_delete(&exports);
    wasm_store_delete(store);
    wasm_engine_delete(engine);
}