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-multi
8
9 Also note that this example was taken from
10 https://github.com/WebAssembly/wasm-c-api/blob/master/example/multi.c
11 originally
12 */
13
14 #include <inttypes.h>
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <string.h>
18 #include <wasm.h>
19 #include <wasmtime.h>
20
21 static void exit_with_error(const char *message, wasmtime_error_t *error,
22 wasm_trap_t *trap);
23
24 // A function to be called from Wasm code.
callback(void * env,wasmtime_caller_t * caller,const wasmtime_val_t * args,size_t nargs,wasmtime_val_t * results,size_t nresults)25 wasm_trap_t *callback(void *env, wasmtime_caller_t *caller,
26 const wasmtime_val_t *args, size_t nargs,
27 wasmtime_val_t *results, size_t nresults) {
28 (void)env;
29 (void)caller;
30 (void)nargs;
31 (void)nresults;
32
33 printf("Calling back...\n");
34 printf("> %" PRIu32 " %" PRIu64 "\n", args[0].of.i32, args[1].of.i64);
35 printf("\n");
36
37 results[0] = args[1];
38 results[1] = args[0];
39 return NULL;
40 }
41
42 // A function closure.
closure_callback(void * env,wasmtime_caller_t * caller,const wasmtime_val_t * args,size_t nargs,wasmtime_val_t * results,size_t nresults)43 wasm_trap_t *closure_callback(void *env, wasmtime_caller_t *caller,
44 const wasmtime_val_t *args, size_t nargs,
45 wasmtime_val_t *results, size_t nresults) {
46 (void)caller;
47 (void)args;
48 (void)nargs;
49 (void)nresults;
50
51 int i = *(int *)env;
52 printf("Calling back closure...\n");
53 printf("> %d\n", i);
54
55 results[0].kind = WASMTIME_I32;
56 results[0].of.i32 = (int32_t)i;
57 return NULL;
58 }
59
main()60 int main() {
61 // Initialize.
62 printf("Initializing...\n");
63 wasm_engine_t *engine = wasm_engine_new();
64 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
65 wasmtime_context_t *context = wasmtime_store_context(store);
66
67 // Load our input file to parse it next
68 FILE *file = fopen("examples/multi.wat", "r");
69 if (!file) {
70 printf("> Error loading file!\n");
71 return 1;
72 }
73 fseek(file, 0L, SEEK_END);
74 size_t file_size = ftell(file);
75 fseek(file, 0L, SEEK_SET);
76 wasm_byte_vec_t wat;
77 wasm_byte_vec_new_uninitialized(&wat, file_size);
78 if (fread(wat.data, file_size, 1, file) != 1) {
79 printf("> Error loading module!\n");
80 return 1;
81 }
82 fclose(file);
83
84 // Parse the wat into the binary wasm format
85 wasm_byte_vec_t binary;
86 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &binary);
87 if (error != NULL)
88 exit_with_error("failed to parse wat", error, NULL);
89 wasm_byte_vec_delete(&wat);
90
91 // Compile.
92 printf("Compiling module...\n");
93 wasmtime_module_t *module = NULL;
94 error =
95 wasmtime_module_new(engine, (uint8_t *)binary.data, binary.size, &module);
96 if (error)
97 exit_with_error("failed to compile module", error, NULL);
98 wasm_byte_vec_delete(&binary);
99
100 // Create external print functions.
101 printf("Creating callback...\n");
102 wasm_functype_t *callback_type =
103 wasm_functype_new_2_2(wasm_valtype_new_i32(), wasm_valtype_new_i64(),
104 wasm_valtype_new_i64(), wasm_valtype_new_i32());
105 wasmtime_func_t callback_func;
106 wasmtime_func_new(context, callback_type, callback, NULL, NULL,
107 &callback_func);
108 wasm_functype_delete(callback_type);
109
110 // Instantiate.
111 printf("Instantiating module...\n");
112 wasmtime_extern_t imports[1];
113 imports[0].kind = WASMTIME_EXTERN_FUNC;
114 imports[0].of.func = callback_func;
115 wasmtime_instance_t instance;
116 wasm_trap_t *trap = NULL;
117 error = wasmtime_instance_new(context, module, imports, 1, &instance, &trap);
118 if (error != NULL || trap != NULL)
119 exit_with_error("failed to instantiate", error, trap);
120 wasmtime_module_delete(module);
121
122 // Extract export.
123 printf("Extracting export...\n");
124 wasmtime_extern_t run;
125 bool ok = wasmtime_instance_export_get(context, &instance, "g", 1, &run);
126 assert(ok);
127 assert(run.kind == WASMTIME_EXTERN_FUNC);
128
129 // Call.
130 printf("Calling export...\n");
131 wasmtime_val_t args[2];
132 args[0].kind = WASMTIME_I32;
133 args[0].of.i32 = 1;
134 args[1].kind = WASMTIME_I64;
135 args[1].of.i64 = 2;
136 wasmtime_val_t results[2];
137 error = wasmtime_func_call(context, &run.of.func, args, 2, results, 2, &trap);
138 if (error != NULL || trap != NULL)
139 exit_with_error("failed to call run", error, trap);
140
141 // Print result.
142 printf("Printing result...\n");
143 printf("> %" PRIu64 " %" PRIu32 "\n", results[0].of.i64, results[1].of.i32);
144
145 assert(results[0].kind == WASMTIME_I64);
146 assert(results[0].of.i64 == 2);
147 assert(results[1].kind == WASMTIME_I32);
148 assert(results[1].of.i32 == 1);
149
150 // Shut down.
151 printf("Shutting down...\n");
152 wasmtime_store_delete(store);
153 wasm_engine_delete(engine);
154
155 // All done.
156 printf("Done.\n");
157 return 0;
158 }
159
exit_with_error(const char * message,wasmtime_error_t * error,wasm_trap_t * trap)160 static void exit_with_error(const char *message, wasmtime_error_t *error,
161 wasm_trap_t *trap) {
162 fprintf(stderr, "error: %s\n", message);
163 wasm_byte_vec_t error_message;
164 if (error != NULL) {
165 wasmtime_error_message(error, &error_message);
166 wasmtime_error_delete(error);
167 } else {
168 wasm_trap_message(trap, &error_message);
169 wasm_trap_delete(trap);
170 }
171 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
172 wasm_byte_vec_delete(&error_message);
173 exit(1);
174 }
175