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123 lines
3.6 KiB
123 lines
3.6 KiB
/*
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Example of instantiating of the WebAssembly module and invoking its exported
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function.
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You can compile and run this example on Linux with:
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cargo build --release -p wasmtime-c-api
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cc examples/gcd.c \
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-I crates/c-api/include \
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-I crates/c-api/wasm-c-api/include \
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target/release/libwasmtime.a \
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-lpthread -ldl -lm \
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-o gcd
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./gcd
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Note that on Windows and macOS the command will be similar, but you'll need
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to tweak the `-lpthread` and such annotations.
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You can also build using cmake:
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mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-gcd
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*/
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <wasm.h>
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#include <wasmtime.h>
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static void exit_with_error(const char *message, wasmtime_error_t *error,
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wasm_trap_t *trap);
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int main() {
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int ret = 0;
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// Set up our context
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wasm_engine_t *engine = wasm_engine_new();
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assert(engine != NULL);
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wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
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assert(store != NULL);
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wasmtime_context_t *context = wasmtime_store_context(store);
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// Load our input file to parse it next
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FILE *file = fopen("examples/gcd.wat", "r");
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if (!file) {
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printf("> Error loading file!\n");
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return 1;
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}
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fseek(file, 0L, SEEK_END);
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size_t file_size = ftell(file);
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fseek(file, 0L, SEEK_SET);
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wasm_byte_vec_t wat;
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wasm_byte_vec_new_uninitialized(&wat, file_size);
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if (fread(wat.data, file_size, 1, file) != 1) {
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printf("> Error loading module!\n");
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return 1;
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}
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fclose(file);
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// Parse the wat into the binary wasm format
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wasm_byte_vec_t wasm;
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wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
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if (error != NULL)
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exit_with_error("failed to parse wat", error, NULL);
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wasm_byte_vec_delete(&wat);
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// Compile and instantiate our module
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wasmtime_module_t *module = NULL;
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error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
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if (module == NULL)
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exit_with_error("failed to compile module", error, NULL);
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wasm_byte_vec_delete(&wasm);
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wasm_trap_t *trap = NULL;
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wasmtime_instance_t instance;
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error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap);
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if (error != NULL || trap != NULL)
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exit_with_error("failed to instantiate", error, trap);
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// Lookup our `gcd` export function
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wasmtime_extern_t gcd;
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bool ok = wasmtime_instance_export_get(context, &instance, "gcd", 3, &gcd);
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assert(ok);
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assert(gcd.kind == WASMTIME_EXTERN_FUNC);
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// And call it!
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int a = 6;
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int b = 27;
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wasmtime_val_t params[2];
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params[0].kind = WASMTIME_I32;
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params[0].of.i32 = a;
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params[1].kind = WASMTIME_I32;
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params[1].of.i32 = b;
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wasmtime_val_t results[1];
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error =
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wasmtime_func_call(context, &gcd.of.func, params, 2, results, 1, &trap);
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if (error != NULL || trap != NULL)
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exit_with_error("failed to call gcd", error, trap);
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assert(results[0].kind == WASMTIME_I32);
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printf("gcd(%d, %d) = %d\n", a, b, results[0].of.i32);
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// Clean up after ourselves at this point
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ret = 0;
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wasmtime_module_delete(module);
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wasmtime_store_delete(store);
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wasm_engine_delete(engine);
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return ret;
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}
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static void exit_with_error(const char *message, wasmtime_error_t *error,
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wasm_trap_t *trap) {
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fprintf(stderr, "error: %s\n", message);
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wasm_byte_vec_t error_message;
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if (error != NULL) {
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wasmtime_error_message(error, &error_message);
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} else {
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wasm_trap_message(trap, &error_message);
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}
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fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
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wasm_byte_vec_delete(&error_message);
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exit(1);
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}
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