110 lines
2.4 KiB
Go
110 lines
2.4 KiB
Go
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package channels
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import "github.com/eapache/queue"
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// ResizableChannel implements the Channel interface with a resizable buffer between the input and the output.
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// The channel initially has a buffer size of 1, but can be resized by calling Resize().
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//
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// Resizing to a buffer capacity of None is, unfortunately, not supported and will panic
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// (see https://github.com/eapache/channels/issues/1).
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// Resizing back and forth between a finite and infinite buffer is fully supported.
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type ResizableChannel struct {
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input, output chan interface{}
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length chan int
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capacity, resize chan BufferCap
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size BufferCap
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buffer *queue.Queue
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}
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func NewResizableChannel() *ResizableChannel {
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ch := &ResizableChannel{
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input: make(chan interface{}),
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output: make(chan interface{}),
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length: make(chan int),
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capacity: make(chan BufferCap),
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resize: make(chan BufferCap),
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size: 1,
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buffer: queue.New(),
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}
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go ch.magicBuffer()
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return ch
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}
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func (ch *ResizableChannel) In() chan<- interface{} {
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return ch.input
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}
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func (ch *ResizableChannel) Out() <-chan interface{} {
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return ch.output
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}
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func (ch *ResizableChannel) Len() int {
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return <-ch.length
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}
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func (ch *ResizableChannel) Cap() BufferCap {
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val, open := <-ch.capacity
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if open {
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return val
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} else {
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return ch.size
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}
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}
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func (ch *ResizableChannel) Close() {
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close(ch.input)
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}
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func (ch *ResizableChannel) Resize(newSize BufferCap) {
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if newSize == None {
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panic("channels: ResizableChannel does not support unbuffered behaviour")
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}
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if newSize < 0 && newSize != Infinity {
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panic("channels: invalid negative size trying to resize channel")
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}
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ch.resize <- newSize
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}
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func (ch *ResizableChannel) magicBuffer() {
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var input, output, nextInput chan interface{}
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var next interface{}
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nextInput = ch.input
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input = nextInput
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for input != nil || output != nil {
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select {
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case elem, open := <-input:
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if open {
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ch.buffer.Add(elem)
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} else {
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input = nil
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nextInput = nil
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}
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case output <- next:
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ch.buffer.Remove()
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case ch.size = <-ch.resize:
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case ch.length <- ch.buffer.Length():
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case ch.capacity <- ch.size:
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}
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if ch.buffer.Length() == 0 {
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output = nil
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next = nil
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} else {
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output = ch.output
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next = ch.buffer.Peek()
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}
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if ch.size != Infinity && ch.buffer.Length() >= int(ch.size) {
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input = nil
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} else {
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input = nextInput
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}
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}
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close(ch.output)
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close(ch.resize)
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close(ch.length)
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close(ch.capacity)
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}
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