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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package agreement
import (
"sort"
"time"
)
// credentialArrivalHistory maintains a circular buffer of time.Duration samples.
type credentialArrivalHistory struct {
history []time.Duration
writePtr int
full bool
}
func makeCredentialArrivalHistory(size int) credentialArrivalHistory {
if size < 0 {
panic("can't create CredentialArrivalHistory with negative size")
}
history := credentialArrivalHistory{history: make([]time.Duration, size)}
history.reset()
return history
}
// store saves a new sample into the circular buffer.
// If the buffer is full, it overwrites the oldest sample.
func (history *credentialArrivalHistory) store(sample time.Duration) {
if len(history.history) == 0 {
return
}
history.history[history.writePtr] = sample
history.writePtr++
if history.writePtr == len(history.history) {
history.full = true
history.writePtr = 0
}
}
// reset marks the history buffer as empty
func (history *credentialArrivalHistory) reset() {
history.writePtr = 0
history.full = false
}
// isFull checks if the circular buffer has been fully populated at least once.
func (history *credentialArrivalHistory) isFull() bool {
return history.full
}
// orderStatistics returns the idx'th time duration in the sorted history array.
// It assumes that history is full and the idx is within the array bounds, and
// panics if either of these assumptions doesn't hold.
func (history *credentialArrivalHistory) orderStatistics(idx int) time.Duration {
if !history.isFull() {
panic("history not full")
}
if idx < 0 || idx >= len(history.history) {
panic("index out of bounds")
}
// if history.history is long, then we could optimize this function to use
// the linear time order statistics algorithm.
sortedArrivals := make([]time.Duration, len(history.history))
copy(sortedArrivals[:], history.history[:])
sort.Slice(sortedArrivals, func(i, j int) bool { return sortedArrivals[i] < sortedArrivals[j] })
return sortedArrivals[idx]
}
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