1 /*
2 Example of instantiating of the WebAssembly module and invoking its exported
3 function.
4
5 You can build using cmake:
6
7 mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-fuel
8 */
9
10 #include <assert.h>
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <wasm.h>
14 #include <wasmtime.h>
15
16 static void exit_with_error(const char *message, wasmtime_error_t *error,
17 wasm_trap_t *trap);
18
main()19 int main() {
20 wasmtime_error_t *error = NULL;
21
22 wasm_config_t *config = wasm_config_new();
23 assert(config != NULL);
24 wasmtime_config_consume_fuel_set(config, true);
25
26 // Create an *engine*, which is a compilation context, with our configured
27 // options.
28 wasm_engine_t *engine = wasm_engine_new_with_config(config);
29 assert(engine != NULL);
30 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
31 assert(store != NULL);
32 wasmtime_context_t *context = wasmtime_store_context(store);
33
34 error = wasmtime_context_set_fuel(context, 10000);
35 if (error != NULL)
36 exit_with_error("failed to set fuel", error, NULL);
37
38 // Load our input file to parse it next
39 FILE *file = fopen("examples/fuel.wat", "r");
40 if (!file) {
41 printf("> Error loading file!\n");
42 return 1;
43 }
44 fseek(file, 0L, SEEK_END);
45 size_t file_size = ftell(file);
46 fseek(file, 0L, SEEK_SET);
47 wasm_byte_vec_t wat;
48 wasm_byte_vec_new_uninitialized(&wat, file_size);
49 if (fread(wat.data, file_size, 1, file) != 1) {
50 printf("> Error loading module!\n");
51 return 1;
52 }
53 fclose(file);
54
55 // Parse the wat into the binary wasm format
56 wasm_byte_vec_t wasm;
57 error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
58 if (error != NULL)
59 exit_with_error("failed to parse wat", error, NULL);
60 wasm_byte_vec_delete(&wat);
61
62 // Compile and instantiate our module
63 wasmtime_module_t *module = NULL;
64 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
65 if (module == NULL)
66 exit_with_error("failed to compile module", error, NULL);
67 wasm_byte_vec_delete(&wasm);
68
69 wasm_trap_t *trap = NULL;
70 wasmtime_instance_t instance;
71 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap);
72 if (error != NULL || trap != NULL)
73 exit_with_error("failed to instantiate", error, trap);
74
75 // Lookup our `fibonacci` export function
76 wasmtime_extern_t fib;
77 bool ok = wasmtime_instance_export_get(context, &instance, "fibonacci",
78 strlen("fibonacci"), &fib);
79 assert(ok);
80 assert(fib.kind == WASMTIME_EXTERN_FUNC);
81
82 // Call it repeatedly until it fails
83 for (int n = 1;; n++) {
84 uint64_t fuel_before;
85 wasmtime_context_get_fuel(context, &fuel_before);
86 wasmtime_val_t params[1];
87 params[0].kind = WASMTIME_I32;
88 params[0].of.i32 = n;
89 wasmtime_val_t results[1];
90 error =
91 wasmtime_func_call(context, &fib.of.func, params, 1, results, 1, &trap);
92 if (error != NULL || trap != NULL) {
93 if (trap != NULL) {
94 wasmtime_trap_code_t code;
95 assert(wasmtime_trap_code(trap, &code));
96 assert(code == WASMTIME_TRAP_CODE_OUT_OF_FUEL);
97 wasm_trap_delete(trap);
98 }
99 if (error != NULL)
100 wasmtime_error_delete(error);
101 printf("Exhausted fuel computing fib(%d)\n", n);
102 break;
103 }
104
105 uint64_t fuel_after;
106 wasmtime_context_get_fuel(context, &fuel_after);
107 assert(results[0].kind == WASMTIME_I32);
108 printf("fib(%d) = %d [consumed %lu fuel]\n", n, results[0].of.i32,
109 fuel_after - fuel_before);
110
111 error = wasmtime_context_set_fuel(context, 10000);
112 if (error != NULL)
113 exit_with_error("failed to set fuel", error, NULL);
114 }
115
116 // Clean up after ourselves at this point
117 wasmtime_module_delete(module);
118 wasmtime_store_delete(store);
119 wasm_engine_delete(engine);
120 return 0;
121 }
122
exit_with_error(const char * message,wasmtime_error_t * error,wasm_trap_t * trap)123 static void exit_with_error(const char *message, wasmtime_error_t *error,
124 wasm_trap_t *trap) {
125 fprintf(stderr, "error: %s\n", message);
126 wasm_byte_vec_t error_message;
127 if (error != NULL) {
128 wasmtime_error_message(error, &error_message);
129 } else {
130 wasm_trap_message(trap, &error_message);
131 }
132 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
133 wasm_byte_vec_delete(&error_message);
134 exit(1);
135 }
136