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/hello.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 hello 14 ./hello 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 as well as the name of the 18 `libwasmtime.a` file on Windows. 19 */ 20 21 #include <assert.h> 22 #include <stdio.h> 23 #include <stdlib.h> 24 #include <wasm.h> 25 #include <wasmtime.h> 26 27 static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap); 28 29 static wasm_trap_t* hello_callback( 30 void *env, 31 wasmtime_caller_t *caller, 32 const wasmtime_val_t* args, 33 size_t nargs, 34 wasmtime_val_t* results, 35 size_t nresults) { 36 printf("Calling back...\n"); 37 printf("> Hello World!\n"); 38 return NULL; 39 } 40 41 int serialize(wasm_byte_vec_t* buffer) { 42 // Set up our compilation context. Note that we could also work with a 43 // `wasm_config_t` here to configure what feature are enabled and various 44 // compilation settings. 45 printf("Initializing...\n"); 46 wasm_engine_t *engine = wasm_engine_new(); 47 assert(engine != NULL); 48 49 // Read our input file, which in this case is a wasm text file. 50 FILE* file = fopen("examples/hello.wat", "r"); 51 assert(file != NULL); 52 fseek(file, 0L, SEEK_END); 53 size_t file_size = ftell(file); 54 fseek(file, 0L, SEEK_SET); 55 wasm_byte_vec_t wat; 56 wasm_byte_vec_new_uninitialized(&wat, file_size); 57 assert(fread(wat.data, file_size, 1, file) == 1); 58 fclose(file); 59 60 // Parse the wat into the binary wasm format 61 wasm_byte_vec_t wasm; 62 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm); 63 if (error != NULL) 64 exit_with_error("failed to parse wat", error, NULL); 65 wasm_byte_vec_delete(&wat); 66 67 // Now that we've got our binary webassembly we can compile our module 68 // and serialize into buffer. 69 printf("Compiling and serializing module...\n"); 70 wasmtime_module_t *module = NULL; 71 error = wasmtime_module_new(engine, (uint8_t*)wasm.data, wasm.size, &module); 72 wasm_byte_vec_delete(&wasm); 73 if (error != NULL) 74 exit_with_error("failed to compile module", error, NULL); 75 error = wasmtime_module_serialize(module, buffer); 76 wasmtime_module_delete(module); 77 if (error != NULL) 78 exit_with_error("failed to serialize module", error, NULL); 79 80 printf("Serialized.\n"); 81 82 wasm_engine_delete(engine); 83 return 0; 84 } 85 86 int deserialize(wasm_byte_vec_t* buffer) { 87 // Set up our compilation context. Note that we could also work with a 88 // `wasm_config_t` here to configure what feature are enabled and various 89 // compilation settings. 90 printf("Initializing...\n"); 91 wasm_engine_t *engine = wasm_engine_new(); 92 assert(engine != NULL); 93 94 // With an engine we can create a *store* which is a long-lived group of wasm 95 // modules. 96 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL); 97 assert(store != NULL); 98 wasmtime_context_t *context = wasmtime_store_context(store); 99 100 // Deserialize compiled module. 101 printf("Deserialize module...\n"); 102 wasmtime_module_t *module = NULL; 103 wasmtime_error_t *error = wasmtime_module_deserialize(engine, (uint8_t*) buffer->data, buffer->size, &module); 104 if (error != NULL) 105 exit_with_error("failed to compile module", error, NULL); 106 107 // Next up we need to create the function that the wasm module imports. Here 108 // we'll be hooking up a thunk function to the `hello_callback` native 109 // function above. 110 printf("Creating callback...\n"); 111 wasm_functype_t *hello_ty = wasm_functype_new_0_0(); 112 wasmtime_func_t hello; 113 wasmtime_func_new(context, hello_ty, hello_callback, NULL, NULL, &hello); 114 115 // With our callback function we can now instantiate the compiled module, 116 // giving us an instance we can then execute exports from. Note that 117 // instantiation can trap due to execution of the `start` function, so we need 118 // to handle that here too. 119 printf("Instantiating module...\n"); 120 wasm_trap_t *trap = NULL; 121 wasmtime_instance_t instance; 122 wasmtime_extern_t imports[1]; 123 imports[0].kind = WASMTIME_EXTERN_FUNC; 124 imports[0].of.func = hello; 125 error = wasmtime_instance_new(context, module, imports, 1, &instance, &trap); 126 if (error != NULL || trap != NULL) 127 exit_with_error("failed to instantiate", error, trap); 128 wasmtime_module_delete(module); 129 130 // Lookup our `run` export function 131 wasmtime_extern_t run; 132 bool ok = wasmtime_instance_export_get(context, &instance, "run", 3, &run); 133 assert(ok); 134 assert(run.kind == WASMTIME_EXTERN_FUNC); 135 136 // And call it! 137 printf("Calling export...\n"); 138 error = wasmtime_func_call(context, &run.of.func, NULL, 0, NULL, 0, &trap); 139 if (error != NULL || trap != NULL) 140 exit_with_error("failed to call function", error, trap); 141 142 // Clean up after ourselves at this point 143 printf("All finished!\n"); 144 145 wasmtime_store_delete(store); 146 wasm_engine_delete(engine); 147 return 0; 148 } 149 150 int main() { 151 wasm_byte_vec_t buffer; 152 if (serialize(&buffer)) { 153 return 1; 154 } 155 if (deserialize(&buffer)) { 156 return 1; 157 } 158 wasm_byte_vec_delete(&buffer); 159 return 0; 160 } 161 162 static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) { 163 fprintf(stderr, "error: %s\n", message); 164 wasm_byte_vec_t error_message; 165 if (error != NULL) { 166 wasmtime_error_message(error, &error_message); 167 wasmtime_error_delete(error); 168 } else { 169 wasm_trap_message(trap, &error_message); 170 wasm_trap_delete(trap); 171 } 172 fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data); 173 wasm_byte_vec_delete(&error_message); 174 exit(1); 175 } 176