This is the Golang implementation of the waPC standard for WebAssembly host runtimes. It allows any WebAssembly module to be loaded as a guest and receive requests for invocation as well as to make its own function requests of the host.
The following is a simple example of synchronous, bidirectional procedure calls between a WebAssembly host runtime and the guest module.
package main
import (
"context"
"fmt"
"os"
"strings"
"github.com/wapc/wapc-go"
"github.com/wapc/wapc-go/engines/wazero"
)
func main() {
if len(os.Args) < 2 {
fmt.Println("usage: hello <name>")
return
}
name := os.Args[1]
ctx := context.Background()
guest, err := os.ReadFile("hello/hello.wasm")
if err != nil {
panic(err)
}
engine := wazero.Engine()
module, err := engine.New(ctx, host, guest, &wapc.ModuleConfig{
Logger: wapc.PrintlnLogger,
Stdout: os.Stdout,
Stderr: os.Stderr,
})
if err != nil {
panic(err)
}
defer module.Close(ctx)
instance, err := module.Instantiate(ctx)
if err != nil {
panic(err)
}
defer instance.Close(ctx)
result, err := instance.Invoke(ctx, "hello", []byte(name))
if err != nil {
panic(err)
}
fmt.Println(string(result))
}
func host(ctx context.Context, binding, namespace, operation string, payload []byte) ([]byte, error) {
// Route the payload to any custom functionality accordingly.
// You can even route to other waPC modules!!!
switch namespace {
case "example":
switch operation {
case "capitalize":
name := string(payload)
name = strings.Title(name)
return []byte(name), nil
}
}
return []byte("default"), nil
}To see this in action, enter the following in your shell:
$ go run example/main.go waPC!
hello called
Hello, WaPC!
Alternatively you can use a Pool to manage a pool of instances.
pool, err := wapc.NewPool(ctx, module, 10, func(instance wapc.Instance) error {
// Do something to initialize this instance before use.
return nil
})
if err != nil {
panic(err)
}
defer pool.Close(ctx)
for i := 0; i < 100; i++ {
instance, err := pool.Get(10 * time.Millisecond)
if err != nil {
panic(err)
}
result, err := instance.Invoke(ctx, "hello", []byte("waPC"))
if err != nil {
panic(err)
}
fmt.Println(string(result))
err = pool.Return(instance)
if err != nil {
panic(err)
}
}While the above example uses wazero, wapc-go is decoupled (via wapc.Engine) and can be used with different runtimes.
Here are the supported wapc.Engine implementations, in alphabetical order:
| Name | Usage | Build Tag | Package |
|---|---|---|---|
| wasmer-go | wasmer.Engine() |
wasmer | github.com/wasmerio/wasmer-go |
| wasmtime-go | wasmtime.Engine() |
wasmtime | github.com/bytecodealliance/wasmtime-go |
| wazero | wazero.Engine() |
N/A | github.com/tetratelabs/wazero |
For example, to switch the engine to wasmer, change example/main.go like below:
--- a/example/main.go
+++ b/example/main.go
@@ -7,7 +7,7 @@ import (
"strings"
"github.com/wapc/wapc-go"
- "github.com/wapc/wapc-go/engines/wazero"
+ "github.com/wapc/wapc-go/engines/wasmer"
)
func main() {
@@ -22,7 +22,7 @@ func main() {
panic(err)
}
- engine := wazero.Engine()
+ engine := wasmer.Engine()
module, err := engine.New(ctx, code, hostCall)
if err != nil {Then, run with its build tag:
$ go run --tags wasmer example/main.go waPC!
hello called
Hello, WaPC!Differences with wapc-rs (Rust)
Besides engine choices, there differences between this library and the Rust implementation:
- Separate compilation (
New) and instantiation (Instantiate) steps. This is to incur the cost of compilation once in a multi-instance scenario. Poolfor creating a pool of instances for a given Module.