1 /* 2 Example of using `externref` values. 3 4 You can compile and run this example on Linux with: 5 6 cargo build --release -p wasmtime-c-api 7 cc examples/externref.c \ 8 -I crates/c-api/include \ 9 -I crates/c-api/wasm-c-api/include \ 10 target/release/libwasmtime.a \ 11 -lpthread -ldl -lm \ 12 -o externref 13 ./externref 14 15 Note that on Windows and macOS the command will be similar, but you'll need 16 to tweak the `-lpthread` and such annotations as well as the name of the 17 `libwasmtime.a` file on Windows. 18 19 You can also build using cmake: 20 21 mkdir build && cd build && cmake .. && \ 22 cmake --build . --target wasmtime-externref 23 */ 24 25 #include <assert.h> 26 #include <stdio.h> 27 #include <stdlib.h> 28 #include <string.h> 29 #include <wasm.h> 30 #include <wasmtime.h> 31 32 static void exit_with_error(const char *message, wasmtime_error_t *error, 33 wasm_trap_t *trap); 34 35 int main() { 36 int ret = 0; 37 bool ok = true; 38 // Create a new configuration with Wasm reference types enabled. 39 printf("Initializing...\n"); 40 wasm_config_t *config = wasm_config_new(); 41 assert(config != NULL); 42 wasmtime_config_wasm_reference_types_set(config, true); 43 44 // Create an *engine*, which is a compilation context, with our configured 45 // options. 46 wasm_engine_t *engine = wasm_engine_new_with_config(config); 47 assert(engine != NULL); 48 49 // With an engine we can create a *store* which is a long-lived group of wasm 50 // modules. 51 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL); 52 assert(store != NULL); 53 wasmtime_context_t *context = wasmtime_store_context(store); 54 55 // Read our input file, which in this case is a wasm text file. 56 FILE *file = fopen("examples/externref.wat", "r"); 57 assert(file != NULL); 58 fseek(file, 0L, SEEK_END); 59 size_t file_size = ftell(file); 60 fseek(file, 0L, SEEK_SET); 61 wasm_byte_vec_t wat; 62 wasm_byte_vec_new_uninitialized(&wat, file_size); 63 if (fread(wat.data, file_size, 1, file) != 1) { 64 printf("> Error loading module!\n"); 65 return 1; 66 } 67 fclose(file); 68 69 // Parse the wat into the binary wasm format 70 wasm_byte_vec_t wasm; 71 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm); 72 if (error != NULL) 73 exit_with_error("failed to parse wat", error, NULL); 74 wasm_byte_vec_delete(&wat); 75 76 // Now that we've got our binary webassembly we can compile our module. 77 printf("Compiling module...\n"); 78 wasmtime_module_t *module = NULL; 79 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module); 80 wasm_byte_vec_delete(&wasm); 81 if (error != NULL) 82 exit_with_error("failed to compile module", error, NULL); 83 84 // Instantiate the module. 85 printf("Instantiating module...\n"); 86 wasm_trap_t *trap = NULL; 87 wasmtime_instance_t instance; 88 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap); 89 if (error != NULL || trap != NULL) 90 exit_with_error("failed to instantiate", error, trap); 91 92 printf("Creating new `externref`...\n"); 93 94 // Create a new `externref` value. 95 // 96 // Note that the NULL here is a finalizer callback, but we don't need one for 97 // this example. 98 wasmtime_externref_t *externref = 99 wasmtime_externref_new("Hello, World!", NULL); 100 101 // The `externref`'s wrapped data should be the string "Hello, World!". 102 void *data = wasmtime_externref_data(externref); 103 assert(strcmp((char *)data, "Hello, World!") == 0); 104 105 printf("Touching `externref` table...\n"); 106 107 wasmtime_extern_t item; 108 109 // Lookup the `table` export. 110 ok = wasmtime_instance_export_get(context, &instance, "table", 111 strlen("table"), &item); 112 assert(ok); 113 assert(item.kind == WASMTIME_EXTERN_TABLE); 114 115 // Set `table[3]` to our `externref`. 116 wasmtime_val_t externref_val; 117 externref_val.kind = WASMTIME_EXTERNREF; 118 externref_val.of.externref = externref; 119 error = wasmtime_table_set(context, &item.of.table, 3, &externref_val); 120 if (error != NULL) 121 exit_with_error("failed to set table", error, NULL); 122 123 // `table[3]` should now be our `externref`. 124 wasmtime_val_t elem; 125 ok = wasmtime_table_get(context, &item.of.table, 3, &elem); 126 assert(ok); 127 assert(elem.kind == WASMTIME_EXTERNREF); 128 assert(strcmp((char *)wasmtime_externref_data(elem.of.externref), 129 "Hello, World!") == 0); 130 wasmtime_val_delete(&elem); 131 132 printf("Touching `externref` global...\n"); 133 134 // Lookup the `global` export. 135 ok = wasmtime_instance_export_get(context, &instance, "global", 136 strlen("global"), &item); 137 assert(ok); 138 assert(item.kind == WASMTIME_EXTERN_GLOBAL); 139 140 // Set the global to our `externref`. 141 error = wasmtime_global_set(context, &item.of.global, &externref_val); 142 if (error != NULL) 143 exit_with_error("failed to set global", error, NULL); 144 145 // Get the global, and it should return our `externref` again. 146 wasmtime_val_t global_val; 147 wasmtime_global_get(context, &item.of.global, &global_val); 148 assert(global_val.kind == WASMTIME_EXTERNREF); 149 assert(strcmp((char *)wasmtime_externref_data(elem.of.externref), 150 "Hello, World!") == 0); 151 wasmtime_val_delete(&global_val); 152 153 printf("Calling `externref` func...\n"); 154 155 // Lookup the `func` export. 156 ok = wasmtime_instance_export_get(context, &instance, "func", strlen("func"), 157 &item); 158 assert(ok); 159 assert(item.kind == WASMTIME_EXTERN_FUNC); 160 161 // And call it! 162 wasmtime_val_t results[1]; 163 error = wasmtime_func_call(context, &item.of.func, &externref_val, 1, results, 164 1, &trap); 165 if (error != NULL || trap != NULL) 166 exit_with_error("failed to call function", error, trap); 167 168 // `func` returns the same reference we gave it, so `results[0]` should be our 169 // `externref`. 170 assert(results[0].kind == WASMTIME_EXTERNREF); 171 assert(strcmp((char *)wasmtime_externref_data(results[0].of.externref), 172 "Hello, World!") == 0); 173 wasmtime_val_delete(&results[0]); 174 175 // We can GC any now-unused references to our externref that the store is 176 // holding. 177 printf("GCing within the store...\n"); 178 wasmtime_context_gc(context); 179 180 // Clean up after ourselves at this point 181 printf("All finished!\n"); 182 ret = 0; 183 184 wasmtime_store_delete(store); 185 wasmtime_module_delete(module); 186 wasm_engine_delete(engine); 187 return 0; 188 } 189 190 static void exit_with_error(const char *message, wasmtime_error_t *error, 191 wasm_trap_t *trap) { 192 fprintf(stderr, "error: %s\n", message); 193 wasm_byte_vec_t error_message; 194 if (error != NULL) { 195 wasmtime_error_message(error, &error_message); 196 wasmtime_error_delete(error); 197 } else { 198 wasm_trap_message(trap, &error_message); 199 wasm_trap_delete(trap); 200 } 201 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data); 202 wasm_byte_vec_delete(&error_message); 203 exit(1); 204 } 205