diff --git a/examples/fuel.c b/examples/fuel.c new file mode 100644 index 0000000000..af3b51782d --- /dev/null +++ b/examples/fuel.c @@ -0,0 +1,132 @@ +/* +Example of instantiating of the WebAssembly module and invoking its exported +function. + +You can compile and run this example on Linux with: + + cargo build --release -p wasmtime-c-api + cc examples/fuel.c \ + -I crates/c-api/include \ + -I crates/c-api/wasm-c-api/include \ + target/release/libwasmtime.a \ + -lpthread -ldl -lm \ + -o fuel + ./fuel + +Note that on Windows and macOS the command will be similar, but you'll need +to tweak the `-lpthread` and such annotations. +*/ + +#include +#include +#include +#include +#include + +static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap); + +int main() { + wasmtime_error_t *error = NULL; + + wasm_config_t *config = wasm_config_new(); + assert(config != NULL); + wasmtime_config_consume_fuel_set(config, true); + + // Create an *engine*, which is a compilation context, with our configured options. + wasm_engine_t *engine = wasm_engine_new_with_config(config); + assert(engine != NULL); + wasm_store_t *store = wasm_store_new(engine); + assert(store != NULL); + error = wasmtime_store_add_fuel(store, 10000); + if (error != NULL) + exit_with_error("failed to add fuel", error, NULL); + + // Load our input file to parse it next + FILE* file = fopen("examples/fuel.wat", "r"); + if (!file) { + printf("> Error loading file!\n"); + return 1; + } + fseek(file, 0L, SEEK_END); + size_t file_size = ftell(file); + fseek(file, 0L, SEEK_SET); + wasm_byte_vec_t wat; + wasm_byte_vec_new_uninitialized(&wat, file_size); + if (fread(wat.data, file_size, 1, file) != 1) { + printf("> Error loading module!\n"); + return 1; + } + fclose(file); + + // Parse the wat into the binary wasm format + wasm_byte_vec_t wasm; + error = wasmtime_wat2wasm(&wat, &wasm); + if (error != NULL) + exit_with_error("failed to parse wat", error, NULL); + wasm_byte_vec_delete(&wat); + + // Compile and instantiate our module + wasm_module_t *module = NULL; + error = wasmtime_module_new(engine, &wasm, &module); + if (module == NULL) + exit_with_error("failed to compile module", error, NULL); + wasm_byte_vec_delete(&wasm); + wasm_trap_t *trap = NULL; + wasm_instance_t *instance = NULL; + wasm_extern_vec_t imports = WASM_EMPTY_VEC; + error = wasmtime_instance_new(store, module, &imports, &instance, &trap); + if (instance == NULL) + exit_with_error("failed to instantiate", error, trap); + + // Lookup our `fibonacci` export function + wasm_extern_vec_t externs; + wasm_instance_exports(instance, &externs); + assert(externs.size == 1); + wasm_func_t *fibonacci = wasm_extern_as_func(externs.data[0]); + assert(fibonacci != NULL); + + // Call it repeatedly until it fails + for (int n = 1; ; n++) { + uint64_t fuel_before; + wasmtime_store_fuel_consumed(store, &fuel_before); + wasm_val_t params[1] = { WASM_I32_VAL(n) }; + wasm_val_t results[1]; + wasm_val_vec_t params_vec = WASM_ARRAY_VEC(params); + wasm_val_vec_t results_vec = WASM_ARRAY_VEC(results); + error = wasmtime_func_call(fibonacci, ¶ms_vec, &results_vec, &trap); + if (error != NULL || trap != NULL) { + printf("Exhausted fuel computing fib(%d)\n", n); + break; + } + + uint64_t fuel_after; + wasmtime_store_fuel_consumed(store, &fuel_after); + assert(results[0].kind == WASM_I32); + printf("fib(%d) = %d [consumed %lld fuel]\n", n, results[0].of.i32, fuel_after - fuel_before); + + error = wasmtime_store_add_fuel(store, fuel_after - fuel_before); + if (error != NULL) + exit_with_error("failed to add fuel", error, NULL); + } + + // Clean up after ourselves at this point + wasm_extern_vec_delete(&externs); + wasm_instance_delete(instance); + wasm_module_delete(module); + wasm_store_delete(store); + wasm_engine_delete(engine); + return 0; +} + +static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) { + fprintf(stderr, "error: %s\n", message); + wasm_byte_vec_t error_message; + if (error != NULL) { + wasmtime_error_message(error, &error_message); + } else { + wasm_trap_message(trap, &error_message); + } + fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data); + wasm_byte_vec_delete(&error_message); + exit(1); +} diff --git a/examples/fuel.rs b/examples/fuel.rs new file mode 100644 index 0000000000..00181a67e1 --- /dev/null +++ b/examples/fuel.rs @@ -0,0 +1,33 @@ +//! Example of limiting a WebAssembly function's runtime using "fuel consumption". + +// You can execute this example with `cargo run --example fuel` + +use anyhow::Result; +use wasmtime::*; + +fn main() -> Result<()> { + let mut config = Config::new(); + config.consume_fuel(true); + let engine = Engine::new(&config)?; + let store = Store::new(&engine); + store.add_fuel(10_000)?; + let module = Module::from_file(store.engine(), "examples/fuel.wat")?; + let instance = Instance::new(&store, &module, &[])?; + + // Invoke `fibonacci` export with higher and higher numbers until we exhaust our fuel. + let fibonacci = instance.get_typed_func::("fibonacci")?; + for n in 1.. { + let fuel_before = store.fuel_consumed().unwrap(); + let output = match fibonacci.call(n) { + Ok(v) => v, + Err(_) => { + println!("Exhausted fuel computing fib({})", n); + break; + } + }; + let fuel_consumed = store.fuel_consumed().unwrap() - fuel_before; + println!("fib({}) = {} [consumed {} fuel]", n, output, fuel_consumed); + store.add_fuel(fuel_consumed)?; + } + Ok(()) +} diff --git a/examples/fuel.wat b/examples/fuel.wat new file mode 100644 index 0000000000..48622c2e21 --- /dev/null +++ b/examples/fuel.wat @@ -0,0 +1,13 @@ +(module + (func $fibonacci (param $n i32) (result i32) + (if + (i32.lt_s (local.get $n) (i32.const 2)) + (return (local.get $n)) + ) + (i32.add + (call $fibonacci (i32.sub (local.get $n) (i32.const 1))) + (call $fibonacci (i32.sub (local.get $n) (i32.const 2))) + ) + ) + (export "fibonacci" (func $fibonacci)) +)