A minimal implementation of v1 WASM spec compatible virtual machine purely written in go. The vm can be embedded in your go program without any dependency like cgo, and enables Gophers to write wasm host environments easily.
The vm should be used only for providing sandbox environments embedded in your Go program since we have not implemented validation of wasm binary.
The implementation is quite straightforward and I hope this code would be a good starting point for novices to learn WASM spec.
func main() {
buf, _ := ioutil.ReadFile("./fib.wasm")
mod, _ := wasm.DecodeModule(bytes.NewBuffer(buf))
mod.BuildIndexSpaces(wasi.Modules) // fd_write must be injected
vm, _ := wasm.NewVM(mod)
for _, c := range []struct {
in, exp int32
}{
{in: 20, exp: 6765},
{in: 10, exp: 55},
{in: 5, exp: 5},
} {
ret, _, _ := vm.ExecExportedFunction("fib", uint64(c.in))
if int32(ret[0]) != c.exp {
panic(fmt.Sprintf("result must be %d but got %d\n", c.exp, ret[0]))
}
}
}func main() {
buf, _ := ioutil.ReadFile("./host_func.wasm")
mod, _ := wasm.DecodeModule(bytes.NewBuffer(buf))
var cnt uint64
hostFunc := func(*wasm.VirtualMachine) reflect.Value {
return reflect.ValueOf(func() {
cnt++
})
}
builder := hostmodule.NewBuilderWith(wasi.Modules)
builder.MustAddFunction("env", "host_func", hostFunc)
mod.BuildIndexSpaces(builder.Done())
vm, _ := wasm.NewVM(mod)
for _, exp := range []uint64{5, 10, 15} {
vm.ExecExportedFunction("call_host_func", exp)
if cnt != exp {
panic(fmt.Sprintf("want %d but got %d", exp, cnt))
}
cnt = 0
}
}WebAssembly System Interface(WASI) will partly be supported in wasi package.
Currently only fd_write is implemented and you can see it works in examples/panic example
where the WASM module causes panic and the host prints the message through fd_write ABI.