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 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 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 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 } 147 148 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 } 159 160 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