traefik/vendor/github.com/eapache/channels/batching_channel.go
2017-03-09 13:13:02 +01:00

87 lines
2.3 KiB
Go

package channels
// BatchingChannel implements the Channel interface, with the change that instead of producing individual elements
// on Out(), it batches together the entire internal buffer each time. Trying to construct an unbuffered batching channel
// will panic, that configuration is not supported (and provides no benefit over an unbuffered NativeChannel).
type BatchingChannel struct {
input, output chan interface{}
length chan int
buffer []interface{}
size BufferCap
}
func NewBatchingChannel(size BufferCap) *BatchingChannel {
if size == None {
panic("channels: BatchingChannel does not support unbuffered behaviour")
}
if size < 0 && size != Infinity {
panic("channels: invalid negative size in NewBatchingChannel")
}
ch := &BatchingChannel{
input: make(chan interface{}),
output: make(chan interface{}),
length: make(chan int),
size: size,
}
go ch.batchingBuffer()
return ch
}
func (ch *BatchingChannel) In() chan<- interface{} {
return ch.input
}
// Out returns a <-chan interface{} in order that BatchingChannel conforms to the standard Channel interface provided
// by this package, however each output value is guaranteed to be of type []interface{} - a slice collecting the most
// recent batch of values sent on the In channel. The slice is guaranteed to not be empty or nil. In practice the net
// result is that you need an additional type assertion to access the underlying values.
func (ch *BatchingChannel) Out() <-chan interface{} {
return ch.output
}
func (ch *BatchingChannel) Len() int {
return <-ch.length
}
func (ch *BatchingChannel) Cap() BufferCap {
return ch.size
}
func (ch *BatchingChannel) Close() {
close(ch.input)
}
func (ch *BatchingChannel) batchingBuffer() {
var input, output, nextInput chan interface{}
nextInput = ch.input
input = nextInput
for input != nil || output != nil {
select {
case elem, open := <-input:
if open {
ch.buffer = append(ch.buffer, elem)
} else {
input = nil
nextInput = nil
}
case output <- ch.buffer:
ch.buffer = nil
case ch.length <- len(ch.buffer):
}
if len(ch.buffer) == 0 {
input = nextInput
output = nil
} else if ch.size != Infinity && len(ch.buffer) >= int(ch.size) {
input = nil
output = ch.output
} else {
input = nextInput
output = ch.output
}
}
close(ch.output)
close(ch.length)
}