81 lines
1.4 KiB
Go
81 lines
1.4 KiB
Go
package node
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import "log"
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type dupCheck struct {
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bitSet
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head int
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tail int
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headCounter uint64
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tailCounter uint64 // Also next expected counter value.
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}
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func newDupCheck(headCounter uint64) *dupCheck {
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return &dupCheck{
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headCounter: headCounter,
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tailCounter: headCounter + 1,
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tail: 1,
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}
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}
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func (dc *dupCheck) IsDup(counter uint64) bool {
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// Before head => it's late, say it's a dup.
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if counter < dc.headCounter {
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log.Printf("Late: %d", counter)
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return true
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}
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// It's within the counter bounds.
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if counter < dc.tailCounter {
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index := (int(counter-dc.headCounter) + dc.head) % bitSetSize
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if dc.Get(index) {
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log.Printf("Dup: %d, %d", counter, dc.tailCounter)
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return true
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}
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dc.Set(index)
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return false
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}
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// It's more than 1 beyond the tail.
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delta := counter - dc.tailCounter
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// Full clear.
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if delta >= bitSetSize {
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dc.ClearAll()
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dc.Set(0)
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dc.tail = 1
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dc.head = 2
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dc.tailCounter = counter + 1
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dc.headCounter = dc.tailCounter - bitSetSize
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return false
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}
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// Clear if necessary.
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for i := 0; i < int(delta); i++ {
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dc.put(false)
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}
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dc.put(true)
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return false
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}
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func (dc *dupCheck) put(set bool) {
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if set {
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dc.Set(dc.tail)
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} else {
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dc.Clear(dc.tail)
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}
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dc.tail = (dc.tail + 1) % bitSetSize
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dc.tailCounter++
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if dc.head == dc.tail {
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dc.head = (dc.head + 1) % bitSetSize
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dc.headCounter++
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}
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}
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