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 .. && \
8 cmake --build . --target wasmtime-serialize
9 */
10
11 #include <assert.h>
12 #include <stdio.h>
13 #include <stdlib.h>
14 #include <wasm.h>
15 #include <wasmtime.h>
16
17 static void exit_with_error(const char *message, wasmtime_error_t *error,
18 wasm_trap_t *trap);
19
hello_callback(void * env,wasmtime_caller_t * caller,const wasmtime_val_t * args,size_t nargs,wasmtime_val_t * results,size_t nresults)20 static wasm_trap_t *hello_callback(void *env, wasmtime_caller_t *caller,
21 const wasmtime_val_t *args, size_t nargs,
22 wasmtime_val_t *results, size_t nresults) {
23 (void)env;
24 (void)caller;
25 (void)args;
26 (void)nargs;
27 (void)results;
28 (void)nresults;
29 printf("Calling back...\n");
30 printf("> Hello World!\n");
31 return NULL;
32 }
33
serialize(wasm_byte_vec_t * buffer)34 int serialize(wasm_byte_vec_t *buffer) {
35 // Set up our compilation context. Note that we could also work with a
36 // `wasm_config_t` here to configure what feature are enabled and various
37 // compilation settings.
38 printf("Initializing...\n");
39 wasm_engine_t *engine = wasm_engine_new();
40 assert(engine != NULL);
41
42 // Read our input file, which in this case is a wasm text file.
43 FILE *file = fopen("examples/hello.wat", "r");
44 assert(file != NULL);
45 fseek(file, 0L, SEEK_END);
46 size_t file_size = ftell(file);
47 fseek(file, 0L, SEEK_SET);
48 wasm_byte_vec_t wat;
49 wasm_byte_vec_new_uninitialized(&wat, file_size);
50 if (fread(wat.data, file_size, 1, file) != 1) {
51 printf("> Error loading module!\n");
52 return 1;
53 }
54 fclose(file);
55
56 // Parse the wat into the binary wasm format
57 wasm_byte_vec_t wasm;
58 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
59 if (error != NULL)
60 exit_with_error("failed to parse wat", error, NULL);
61 wasm_byte_vec_delete(&wat);
62
63 // Now that we've got our binary webassembly we can compile our module
64 // and serialize into buffer.
65 printf("Compiling and serializing module...\n");
66 wasmtime_module_t *module = NULL;
67 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
68 wasm_byte_vec_delete(&wasm);
69 if (error != NULL)
70 exit_with_error("failed to compile module", error, NULL);
71 error = wasmtime_module_serialize(module, buffer);
72 wasmtime_module_delete(module);
73 if (error != NULL)
74 exit_with_error("failed to serialize module", error, NULL);
75
76 printf("Serialized.\n");
77
78 wasm_engine_delete(engine);
79 return 0;
80 }
81
deserialize(wasm_byte_vec_t * buffer)82 int deserialize(wasm_byte_vec_t *buffer) {
83 // Set up our compilation context. Note that we could also work with a
84 // `wasm_config_t` here to configure what feature are enabled and various
85 // compilation settings.
86 printf("Initializing...\n");
87 wasm_engine_t *engine = wasm_engine_new();
88 assert(engine != NULL);
89
90 // With an engine we can create a *store* which is a long-lived group of wasm
91 // modules.
92 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
93 assert(store != NULL);
94 wasmtime_context_t *context = wasmtime_store_context(store);
95
96 // Deserialize compiled module.
97 printf("Deserialize module...\n");
98 wasmtime_module_t *module = NULL;
99 wasmtime_error_t *error = wasmtime_module_deserialize(
100 engine, (uint8_t *)buffer->data, buffer->size, &module);
101 if (error != NULL)
102 exit_with_error("failed to compile module", error, NULL);
103
104 // Next up we need to create the function that the wasm module imports. Here
105 // we'll be hooking up a thunk function to the `hello_callback` native
106 // function above.
107 printf("Creating callback...\n");
108 wasm_functype_t *hello_ty = wasm_functype_new_0_0();
109 wasmtime_func_t hello;
110 wasmtime_func_new(context, hello_ty, hello_callback, NULL, NULL, &hello);
111 wasm_functype_delete(hello_ty);
112
113 // With our callback function we can now instantiate the compiled module,
114 // giving us an instance we can then execute exports from. Note that
115 // instantiation can trap due to execution of the `start` function, so we need
116 // to handle that here too.
117 printf("Instantiating module...\n");
118 wasm_trap_t *trap = NULL;
119 wasmtime_instance_t instance;
120 wasmtime_extern_t imports[1];
121 imports[0].kind = WASMTIME_EXTERN_FUNC;
122 imports[0].of.func = hello;
123 error = wasmtime_instance_new(context, module, imports, 1, &instance, &trap);
124 if (error != NULL || trap != NULL)
125 exit_with_error("failed to instantiate", error, trap);
126 wasmtime_module_delete(module);
127
128 // Lookup our `run` export function
129 wasmtime_extern_t run;
130 bool ok = wasmtime_instance_export_get(context, &instance, "run", 3, &run);
131 assert(ok);
132 assert(run.kind == WASMTIME_EXTERN_FUNC);
133
134 // And call it!
135 printf("Calling export...\n");
136 error = wasmtime_func_call(context, &run.of.func, NULL, 0, NULL, 0, &trap);
137 if (error != NULL || trap != NULL)
138 exit_with_error("failed to call function", error, trap);
139
140 // Clean up after ourselves at this point
141 printf("All finished!\n");
142
143 wasmtime_store_delete(store);
144 wasm_engine_delete(engine);
145 return 0;
146 }
147
main()148 int main() {
149 wasm_byte_vec_t buffer;
150 if (serialize(&buffer)) {
151 return 1;
152 }
153 if (deserialize(&buffer)) {
154 return 1;
155 }
156 wasm_byte_vec_delete(&buffer);
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