85 lines
1.9 KiB
Go
85 lines
1.9 KiB
Go
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package fun
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import (
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"reflect"
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"github.com/BurntSushi/ty"
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)
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// AsyncChan has a parametric type:
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//
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// func AsyncChan(chan A) (send chan<- A, recv <-chan A)
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//
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// AsyncChan provides a channel abstraction without a fixed size buffer.
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// The input should be a pointer to a channel that has a type without a
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// direction, e.g., `new(chan int)`. Two new channels are returned: `send` and
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// `recv`. The caller must send data on the `send` channel and receive data on
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// the `recv` channel.
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//
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// Implementation is inspired by Kyle Lemons' work:
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// https://github.com/kylelemons/iq/blob/master/iq_slice.go
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func AsyncChan(baseChan interface{}) (send, recv interface{}) {
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chk := ty.Check(
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new(func(*chan ty.A) (chan ty.A, chan ty.A)),
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baseChan)
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// We don't care about the baseChan---it is only used to construct
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// the return types.
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tsend, trecv := chk.Returns[0], chk.Returns[1]
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buf := make([]reflect.Value, 0, 10)
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rsend := reflect.MakeChan(tsend, 0)
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rrecv := reflect.MakeChan(trecv, 0)
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go func() {
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defer rrecv.Close()
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BUFLOOP:
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for {
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if len(buf) == 0 {
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rv, ok := rsend.Recv()
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if !ok {
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break BUFLOOP
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}
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buf = append(buf, rv)
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}
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cases := []reflect.SelectCase{
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// case v, ok := <-send
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{
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Dir: reflect.SelectRecv,
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Chan: rsend,
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},
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// case recv <- buf[0]
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{
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Dir: reflect.SelectSend,
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Chan: rrecv,
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Send: buf[0],
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},
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}
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choice, rval, rok := reflect.Select(cases)
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switch choice {
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case 0:
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// case v, ok := <-send
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if !rok {
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break BUFLOOP
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}
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buf = append(buf, rval)
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case 1:
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// case recv <- buf[0]
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buf = buf[1:]
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default:
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panic("bug")
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}
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}
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for _, rv := range buf {
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rrecv.Send(rv)
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}
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}()
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// Create the directional channel types.
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tsDir := reflect.ChanOf(reflect.SendDir, tsend.Elem())
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trDir := reflect.ChanOf(reflect.RecvDir, trecv.Elem())
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return rsend.Convert(tsDir).Interface(), rrecv.Convert(trDir).Interface()
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}
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