WASI

You can also browse this source code online and clone the wasmtime repository to run the example locally:

This example shows off how to instantiate a wasm module using WASI imports.

Wasm Source

use std::thread::sleep;
use std::time::{Duration, Instant};

fn main() {
    println!("Hello, world!");
    let start = Instant::now();
    sleep(Duration::from_millis(100));
    println!("Napped for {:?}", Instant::now().duration_since(start));
}

Host Source

//! Example of instantiating a wasm module which uses WASI imports.

/*
You can execute this example with:
    cmake examples/
    cargo run --example wasip1
*/

use wasmtime::*;
use wasmtime_wasi::WasiCtx;

fn main() -> Result<()> {
    // Define the WASI functions globally on the `Config`.
    let engine = Engine::default();
    let mut linker = Linker::new(&engine);
    wasmtime_wasi::p1::add_to_linker_sync(&mut linker, |s| s)?;

    // Create a WASI context and put it in a Store; all instances in the store
    // share this context. `WasiCtxBuilder` provides a number of ways to
    // configure what the target program will have access to.
    let wasi = WasiCtx::builder().inherit_stdio().inherit_args().build_p1();
    let mut store = Store::new(&engine, wasi);

    // Instantiate our module with the imports we've created, and run it.
    let module = Module::from_file(&engine, "target/wasm32-wasip1/debug/wasi.wasm")?;
    linker.module(&mut store, "", &module)?;
    linker
        .get_default(&mut store, "")?
        .typed::<(), ()>(&store)?
        .call(&mut store, ())?;

    Ok(())
}
/*
Example of instantiating a WebAssembly which uses WASI imports.

You can compile and run this example on Linux with:

   cmake examples/
   cargo build --release -p wasmtime-c-api
   cc examples/wasip1/main.c \
       -I crates/c-api/include \
       target/release/libwasmtime.a \
       -lpthread -ldl -lm \
       -o wasip1
   ./wasip1

Note that on Windows and macOS the command will be similar, but you'll need
to tweak the `-lpthread` and such annotations.

You can also build using cmake:

mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-wasip1
*/

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <wasi.h>
#include <wasm.h>
#include <wasmtime.h>

#define MIN(a, b) ((a) < (b) ? (a) : (b))

static void exit_with_error(const char *message, wasmtime_error_t *error,
                            wasm_trap_t *trap);

int main() {
  // Set up our context
  wasm_engine_t *engine = wasm_engine_new();
  assert(engine != NULL);
  wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
  assert(store != NULL);
  wasmtime_context_t *context = wasmtime_store_context(store);

  // Create a linker with WASI functions defined
  wasmtime_linker_t *linker = wasmtime_linker_new(engine);
  wasmtime_error_t *error = wasmtime_linker_define_wasi(linker);
  if (error != NULL)
    exit_with_error("failed to link wasi", error, NULL);

  wasm_byte_vec_t wasm;
  // Load our input file to parse it next
  FILE *file = fopen("target/wasm32-wasip1/debug/wasi.wasm", "rb");
  if (!file) {
    printf("> Error loading file!\n");
    exit(1);
  }
  fseek(file, 0L, SEEK_END);
  size_t file_size = ftell(file);
  wasm_byte_vec_new_uninitialized(&wasm, file_size);
  fseek(file, 0L, SEEK_SET);
  if (fread(wasm.data, file_size, 1, file) != 1) {
    printf("> Error loading module!\n");
    exit(1);
  }
  fclose(file);

  // Compile our modules
  wasmtime_module_t *module = NULL;
  error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
  if (!module)
    exit_with_error("failed to compile module", error, NULL);
  wasm_byte_vec_delete(&wasm);

  // Instantiate wasi
  wasi_config_t *wasi_config = wasi_config_new();
  assert(wasi_config);
  wasi_config_inherit_argv(wasi_config);
  wasi_config_inherit_env(wasi_config);
  wasi_config_inherit_stdin(wasi_config);
  wasi_config_inherit_stdout(wasi_config);
  wasi_config_inherit_stderr(wasi_config);
  wasm_trap_t *trap = NULL;
  error = wasmtime_context_set_wasi(context, wasi_config);
  if (error != NULL)
    exit_with_error("failed to instantiate WASI", error, NULL);

  // Instantiate the module
  error = wasmtime_linker_module(linker, context, "", 0, module);
  if (error != NULL)
    exit_with_error("failed to instantiate module", error, NULL);

  // Run it.
  wasmtime_func_t func;
  error = wasmtime_linker_get_default(linker, context, "", 0, &func);
  if (error != NULL)
    exit_with_error("failed to locate default export for module", error, NULL);

  error = wasmtime_func_call(context, &func, NULL, 0, NULL, 0, &trap);
  if (error != NULL || trap != NULL)
    exit_with_error("error calling default export", error, trap);

  // Clean up after ourselves at this point
  wasmtime_module_delete(module);
  wasmtime_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);
    wasmtime_error_delete(error);
  } else {
    wasm_trap_message(trap, &error_message);
    wasm_trap_delete(trap);
  }
  fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
  wasm_byte_vec_delete(&error_message);
  exit(1);
}

/*
Example of instantiating a wasm module which uses WASI imports.

You can build the example using CMake:

mkdir build && (cd build && cmake .. && \
  cmake --build . --target wasmtime-wasip1-cpp)

And then run it:

build/wasmtime-wasip1-cpp
*/

#include <fstream>
#include <iostream>
#include <sstream>
#include <vector>
#include <wasmtime.hh>

using namespace wasmtime;

static std::vector<uint8_t> read_binary_file(const char *path) {
  std::ifstream file(path, std::ios::in | std::ios::binary);
  if (!file.is_open()) {
    throw std::runtime_error(std::string("failed to open wasm file: ") + path);
  }
  std::vector<uint8_t> data((std::istreambuf_iterator<char>(file)),
                            std::istreambuf_iterator<char>());
  return data;
}

int main() {
  // Define the WASI functions globally on the `Config`.
  Engine engine;
  Linker linker(engine);
  linker.define_wasi().unwrap();

  // Create a WASI context and put it in a Store; all instances in the store
  // share this context. `WasiConfig` provides a number of ways to
  // configure what the target program will have access to.
  WasiConfig wasi;
  wasi.inherit_argv();
  wasi.inherit_stdin();
  wasi.inherit_stdout();
  wasi.inherit_stderr();

  Store store(engine);
  store.context().set_wasi(std::move(wasi)).unwrap();

  // Load and compile the wasm module.
  auto bytes = read_binary_file("target/wasm32-wasip1/debug/wasi.wasm");
  auto module =
      Module::compile(engine, Span<uint8_t>(bytes.data(), bytes.size()))
          .unwrap();

  // Define the module in the linker (anonymous name matches Rust example
  // usage).
  linker.module(store.context(), "", module).unwrap();

  // Get the default export (command entrypoint) and invoke it.
  Func default_func = linker.get_default(store.context(), "").unwrap();
  default_func.call(store, {}).unwrap();

  return 0;
}