83 lines
1.6 KiB
Go
83 lines
1.6 KiB
Go
package connection
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import "sync"
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type MessageBuffer struct {
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messages []message
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getIndex int
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insertIndex int
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size int
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newDataInserted chan bool
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firstWriteHappened bool
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cond *sync.Cond
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}
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type message struct {
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content string
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new bool
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}
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func newMessageBuffer(size int) *MessageBuffer {
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cond := sync.NewCond(&sync.Mutex{})
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return &MessageBuffer{
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messages: make([]message, size),
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size: size,
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getIndex: 0,
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insertIndex: 0,
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newDataInserted: make(chan bool),
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firstWriteHappened: false,
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cond: cond,
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}
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}
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func (b *MessageBuffer) Insert(msg string) {
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b.cond.L.Lock()
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defer b.cond.L.Unlock()
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oldMessage := b.messages[b.insertIndex]
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b.messages[b.insertIndex] = message{content: msg, new: true}
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if b.firstWriteHappened &&
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b.insertIndex == b.getIndex &&
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oldMessage.new { // insertIndex caught up with getIndex
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b.getIndex = b.incrementAndWrapIndex(b.getIndex)
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}
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b.insertIndex = b.incrementAndWrapIndex(b.insertIndex)
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b.firstWriteHappened = true
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b.cond.Broadcast()
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}
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func (b *MessageBuffer) Get() (string, error) {
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b.cond.L.Lock()
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defer b.cond.L.Unlock()
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if !b.firstWriteHappened {
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b.cond.Wait()
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}
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var msg *message
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for {
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msg = &b.messages[b.getIndex]
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if msg.new {
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msg.new = false
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break
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}
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b.cond.Wait()
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}
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b.getIndex = b.incrementAndWrapIndex(b.getIndex)
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return msg.content, nil
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}
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func (b MessageBuffer) incrementAndWrapIndex(index int) int {
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newIndex := index + 1
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if newIndex == b.size {
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newIndex = 0
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}
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return newIndex
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}
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