github.com/bananabytelabs/wazero@v0.0.0-20240105073314-54b22a776da8/imports/wasi_snapshot_preview1/example_test.go (about)

     1  package wasi_snapshot_preview1_test
     2  
     3  import (
     4  	"context"
     5  	_ "embed"
     6  	"fmt"
     7  	"os"
     8  
     9  	"github.com/bananabytelabs/wazero"
    10  	"github.com/bananabytelabs/wazero/imports/wasi_snapshot_preview1"
    11  	"github.com/bananabytelabs/wazero/sys"
    12  )
    13  
    14  // exitOnStartWasm was generated by the following:
    15  //
    16  //	cd testdata; wat2wasm --debug-names exit_on_start.wat
    17  //
    18  //go:embed testdata/exit_on_start.wasm
    19  var exitOnStartWasm []byte
    20  
    21  // This is an example of how to use WebAssembly System Interface (WASI) with its simplest function: "proc_exit".
    22  //
    23  // See https://github.com/bananabytelabs/wazero/tree/main/examples/wasi for another example.
    24  func Example() {
    25  	// Choose the context to use for function calls.
    26  	ctx := context.Background()
    27  
    28  	// Create a new WebAssembly Runtime.
    29  	r := wazero.NewRuntime(ctx)
    30  	defer r.Close(ctx)
    31  
    32  	// Instantiate WASI, which implements system I/O such as console output.
    33  	wasi_snapshot_preview1.MustInstantiate(ctx, r)
    34  
    35  	// InstantiateModule runs the "_start" function which is like a "main" function.
    36  	mod, err := r.InstantiateWithConfig(ctx, exitOnStartWasm,
    37  		// Override default configuration (which discards stdout).
    38  		wazero.NewModuleConfig().WithStdout(os.Stdout).WithName("wasi-demo"))
    39  	if mod != nil {
    40  		defer r.Close(ctx)
    41  	}
    42  
    43  	// Note: Most compilers do not exit the module after running "_start", unless
    44  	// there was an error. This allows you to call exported functions.
    45  	if exitErr, ok := err.(*sys.ExitError); ok {
    46  		fmt.Printf("exit_code: %d\n", exitErr.ExitCode())
    47  	}
    48  
    49  	// Output:
    50  	// exit_code: 2
    51  }