github.com/bananabytelabs/wazero@v0.0.0-20240105073314-54b22a776da8/experimental/gojs/example/cat.go (about)

     1  package main
     2  
     3  import (
     4  	"context"
     5  	"log"
     6  	"os"
     7  	"path"
     8  	"testing/fstest"
     9  	"time"
    10  
    11  	"github.com/bananabytelabs/wazero"
    12  	"github.com/bananabytelabs/wazero/experimental/gojs"
    13  )
    14  
    15  // main invokes Wasm compiled via `GOOS=js GOARCH=wasm`, which writes an input
    16  // file to stdout, just like `cat`.
    17  //
    18  // This shows how to integrate a filesystem with wasm using gojs.
    19  func main() {
    20  	// Read the binary compiled with `GOOS=js GOARCH=wasm`.
    21  	bin, err := os.ReadFile(path.Join("cat", "main.wasm"))
    22  	if err != nil {
    23  		log.Panicln(err)
    24  	}
    25  
    26  	// Choose the context to use for function calls.
    27  	ctx := context.Background()
    28  
    29  	// Create a new WebAssembly Runtime.
    30  	r := wazero.NewRuntime(ctx)
    31  	defer r.Close(ctx) // This closes everything this Runtime created.
    32  
    33  	// Compile the wasm binary to machine code.
    34  	start := time.Now()
    35  	guest, err := r.CompileModule(ctx, bin)
    36  	if err != nil {
    37  		log.Panicln(err)
    38  	}
    39  	compilationTime := time.Since(start).Milliseconds()
    40  	log.Printf("CompileModule took %dms", compilationTime)
    41  
    42  	// Instantiate the host functions needed by the guest.
    43  	start = time.Now()
    44  	gojs.MustInstantiate(ctx, r, guest)
    45  	instantiateTime := time.Since(start).Milliseconds()
    46  	log.Printf("gojs.MustInstantiate took %dms", instantiateTime)
    47  
    48  	fakeFilesystem := fstest.MapFS{"test.txt": {Data: []byte("greet filesystem\n")}}
    49  
    50  	// Create the sandbox configuration used by the guest.
    51  	guestConfig := wazero.NewModuleConfig().
    52  		// By default, I/O streams are discarded and there's no file system.
    53  		WithStdout(os.Stdout).WithStderr(os.Stderr).
    54  		WithFS(fakeFilesystem).
    55  		WithArgs("gojs", os.Args[1]) // only what's in the filesystem will work!
    56  
    57  	// Execute the "run" function, which corresponds to "main" in stars/main.go.
    58  	start = time.Now()
    59  	err = gojs.Run(ctx, r, guest, gojs.NewConfig(guestConfig))
    60  	runTime := time.Since(start).Milliseconds()
    61  	log.Printf("gojs.Run took %dms", runTime)
    62  	if err != nil {
    63  		log.Panicln(err)
    64  	}
    65  }