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port.go
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port.go
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package wrpcnet
import (
"container/list"
"errors"
"io"
"runtime"
"syscall/js"
"github.com/mgnsk/go-wasm-demos/pkg/array"
"github.com/mgnsk/go-wasm-demos/pkg/jsutil"
)
// MessagePort is a synchronous JS MessagePort wrapper.
type MessagePort struct {
Value js.Value
messages *list.List
notify chan struct{}
ack chan struct{}
done chan struct{}
err error
}
// Pipe returns a synchronous duplex MessagePort pipe.
func Pipe() (*MessagePort, *MessagePort) {
ch := js.Global().Get("MessageChannel").New()
p1 := NewMessagePort(ch.Get("port1"))
p2 := NewMessagePort(ch.Get("port2"))
return p1, p2
}
// NewMessagePort creates a synchronous JS MessagePort wrapper.
func NewMessagePort(value js.Value) *MessagePort {
p := &MessagePort{
Value: value,
messages: list.New(),
notify: make(chan struct{}),
ack: make(chan struct{}),
done: make(chan struct{}),
}
onError := js.FuncOf(p.onError)
onMessageError := js.FuncOf(p.onError)
onMessage := js.FuncOf(p.onMessage)
value.Set("onerror", onError)
value.Set("onmessageerror", onMessageError)
value.Set("onmessage", onMessage)
runtime.SetFinalizer(p, func(any) {
onError.Release()
onMessageError.Release()
onMessage.Release()
})
return p
}
// ReadMessage reads a single message or error from the port.
func (p *MessagePort) ReadMessage() (js.Value, error) {
select {
case <-p.done:
return js.Value{}, p.err
case <-p.notify:
p.Value.Call("postMessage", map[string]any{"__ack": true})
msg := p.messages.Remove(p.messages.Front()).(js.Value)
jsutil.ConsoleLog("readMessage", msg)
return msg, nil
}
}
// WriteMessage writes a messages into the port.
// It blocks until the remote side reads the message.
func (p *MessagePort) WriteMessage(messages map[string]any, transferables []any) error {
p.Value.Call("postMessage", messages, transferables)
select {
case <-p.done:
// jsutil.ConsoleLog("postMessage error", p.err.Error())
return p.err
case <-p.ack:
jsutil.ConsoleLog("postMessage ack")
return nil
}
}
// Read a byte array message from the port.
func (p *MessagePort) Read(b []byte) (n int, err error) {
msg, err := p.ReadMessage()
if err != nil {
return 0, err
}
ab := msg.Get("arr")
if ab.IsUndefined() {
panic("expected an ArrayBuffer message")
}
arr := array.NewUint8Array(ab)
if arr.Len() > len(b) {
p.messages.PushFront(msg)
return 0, io.ErrShortBuffer
}
return arr.CopyBytesToGo(b), nil
}
// Write a byte array message into the port.
func (p *MessagePort) Write(b []byte) (n int, err error) {
ab := array.NewFromSlice(b).ArrayBuffer()
messages := map[string]any{"arr": ab}
transferables := []any{ab}
if err := p.WriteMessage(messages, transferables); err != nil {
return 0, err
}
return len(b), nil
}
// Close the port. All pending reads and writes are unblocked and return io.ErrClosedPipe.
func (p *MessagePort) Close() error {
p.err = io.ErrClosedPipe
close(p.done)
p.Value.Call("postMessage", map[string]any{"__eof": true})
p.Value.Call("close")
return nil
}
// CloseWithError writes an error message into the port and closes the port.
// All pending reads and writes are unblocked and return io.ErrClosedPipe.
func (p *MessagePort) CloseWithError(err error) {
p.err = io.ErrClosedPipe
close(p.done)
p.Value.Call("postMessage", map[string]any{"__err": err.Error()})
p.Value.Call("close")
}
func (p *MessagePort) onError(_ js.Value, args []js.Value) any {
if p.err == nil {
p.err = js.Error{Value: args[0]}
close(p.done)
}
return nil
}
func (p *MessagePort) onMessage(this js.Value, args []js.Value) any {
data := args[0].Get("data")
eof := data.Get("__eof")
err := data.Get("__err")
ack := data.Get("__ack")
switch {
case !eof.IsUndefined():
if p.err == nil {
p.err = io.EOF
close(p.done)
}
case !err.IsUndefined():
if p.err == nil {
p.err = errors.New(err.String())
close(p.done)
}
case !ack.IsUndefined():
go func() {
select {
case <-p.done:
case p.ack <- struct{}{}:
}
}()
default:
p.messages.PushBack(data)
go func() {
select {
case <-p.done:
case p.notify <- struct{}{}:
}
}()
}
return nil
}