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output_cache.go
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/
output_cache.go
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//Caches gocmc.CoreMidiEndpoints so that we're not constantly
//creating new output ports, etc when all that changes on an output
//is often the midi channel.
package main
import (
"fmt"
"github.com/j14159/gocmc"
)
//Holds details for the asynchronous cache request, you should
//use OutputCache.GetOutput instead of dealing with this directly.
type OutputRequest struct {
outputName string
midiChannel int
replyChannel chan gocmc.Output
}
//Holds the CoreMIDI client and cache's request channel. Use NewOutputCache
//rather than constructing this directly _unless_ you don't want the
//underlying go routine started to handle cache requests right away.
type OutputCache struct {
client gocmc.Client
requestChannel chan OutputRequest
}
//Creates a new OutputCache and spins up the underlying go routine.
func NewOutputCache(client gocmc.Client) (cache OutputCache) {
requestChan := make(chan OutputRequest)
cache = OutputCache{client, requestChan}
go cache.outputCacheHandler()
return
}
//Convenience method so that users of an OutputCache don't need to deal
//directly with channels and OutputRequests. Same idea behind
//gen_server:call in a way.
func (cache OutputCache) GetOutput(outputName string, midiChannel int) gocmc.Output {
replyChan := make(chan gocmc.Output)
cache.requestChannel <- OutputRequest{outputName, midiChannel, replyChan}
return <-replyChan
}
//Run this as a go routine to handle asynchronous output
//cache requests.
func (cache OutputCache) outputCacheHandler() {
_cache := make(map[string]map[int]gocmc.Output)
for true {
select {
case req := <-cache.requestChannel:
//have we cached _anything_ for this output yet?
if outputs, outputCached := _cache[req.outputName]; outputCached {
if output, exists := outputs[req.midiChannel]; exists {
req.replyChannel <- output
} else {
fmt.Printf("New channel for %s\n", req.outputName)
destination := gocmc.GetDestinations()[req.outputName].Endpoint
output := cache.client.NewOutput(req.outputName+"-output", req.midiChannel, destination)
outputs[req.midiChannel] = output
_cache[req.outputName] = outputs
req.replyChannel <- output
}
} else {
fmt.Println("No existing output, creating")
destination := gocmc.GetDestinations()[req.outputName].Endpoint
output := cache.client.NewOutput(req.outputName+"-output", req.midiChannel, destination)
fmt.Println("New output: ", output)
outputs := make(map[int]gocmc.Output)
outputs[req.midiChannel] = output
_cache[req.outputName] = outputs
req.replyChannel <- output
}
}
}
}