1 /* 2 Example of instantiating of the WebAssembly module and invoking its exported 3 function. 4 5 You can compile and run this example on Linux with: 6 7 cargo build --release -p wasmtime-c-api 8 cc examples/gcd.c \ 9 -I crates/c-api/include \ 10 -I crates/c-api/wasm-c-api/include \ 11 target/release/libwasmtime.a \ 12 -lpthread -ldl -lm \ 13 -o gcd 14 ./gcd 15 16 Note that on Windows and macOS the command will be similar, but you'll need 17 to tweak the `-lpthread` and such annotations. 18 */ 19 20 #include <assert.h> 21 #include <stdio.h> 22 #include <stdlib.h> 23 #include <wasm.h> 24 #include <wasmtime.h> 25 26 static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap); 27 28 int main() { 29 int ret = 0; 30 // Set up our context 31 wasm_engine_t *engine = wasm_engine_new(); 32 assert(engine != NULL); 33 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL); 34 assert(store != NULL); 35 wasmtime_context_t *context = wasmtime_store_context(store); 36 37 // Load our input file to parse it next 38 FILE* file = fopen("examples/gcd.wat", "r"); 39 if (!file) { 40 printf("> Error loading file!\n"); 41 return 1; 42 } 43 fseek(file, 0L, SEEK_END); 44 size_t file_size = ftell(file); 45 fseek(file, 0L, SEEK_SET); 46 wasm_byte_vec_t wat; 47 wasm_byte_vec_new_uninitialized(&wat, file_size); 48 if (fread(wat.data, file_size, 1, file) != 1) { 49 printf("> Error loading module!\n"); 50 return 1; 51 } 52 fclose(file); 53 54 // Parse the wat into the binary wasm format 55 wasm_byte_vec_t wasm; 56 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm); 57 if (error != NULL) 58 exit_with_error("failed to parse wat", error, NULL); 59 wasm_byte_vec_delete(&wat); 60 61 // Compile and instantiate our module 62 wasmtime_module_t *module = NULL; 63 error = wasmtime_module_new(engine, (uint8_t*) wasm.data, wasm.size, &module); 64 if (module == NULL) 65 exit_with_error("failed to compile module", error, NULL); 66 wasm_byte_vec_delete(&wasm); 67 68 wasm_trap_t *trap = NULL; 69 wasmtime_instance_t instance; 70 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap); 71 if (error != NULL || trap != NULL) 72 exit_with_error("failed to instantiate", error, trap); 73 74 // Lookup our `gcd` export function 75 wasmtime_extern_t gcd; 76 bool ok = wasmtime_instance_export_get(context, &instance, "gcd", 3, &gcd); 77 assert(ok); 78 assert(gcd.kind == WASMTIME_EXTERN_FUNC); 79 80 // And call it! 81 int a = 6; 82 int b = 27; 83 wasmtime_val_t params[2]; 84 params[0].kind = WASMTIME_I32; 85 params[0].of.i32 = a; 86 params[1].kind = WASMTIME_I32; 87 params[1].of.i32 = b; 88 wasmtime_val_t results[1]; 89 error = wasmtime_func_call(context, &gcd.of.func, params, 2, results, 1, &trap); 90 if (error != NULL || trap != NULL) 91 exit_with_error("failed to call gcd", error, trap); 92 assert(results[0].kind == WASMTIME_I32); 93 94 printf("gcd(%d, %d) = %d\n", a, b, results[0].of.i32); 95 96 // Clean up after ourselves at this point 97 ret = 0; 98 99 wasmtime_module_delete(module); 100 wasmtime_store_delete(store); 101 wasm_engine_delete(engine); 102 return ret; 103 } 104 105 static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) { 106 fprintf(stderr, "error: %s\n", message); 107 wasm_byte_vec_t error_message; 108 if (error != NULL) { 109 wasmtime_error_message(error, &error_message); 110 } else { 111 wasm_trap_message(trap, &error_message); 112 } 113 fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data); 114 wasm_byte_vec_delete(&error_message); 115 exit(1); 116 } 117