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- // Copyright (c) 2012-2014 Jeremy Latt
- // Copyright (c) 2016 Daniel Oaks <daniel@danieloaks.net>
- // released under the MIT license
-
- package irc
-
- import (
- "sync"
- )
-
- // WhoWasList holds our list of prior clients (for use with the WHOWAS command).
- type WhoWasList struct {
- buffer []WhoWas
- // three possible states:
- // empty: start == end == -1
- // partially full: start != end
- // full: start == end > 0
- // if entries exist, they go from `start` to `(end - 1) % length`
- start int
- end int
-
- accessMutex sync.RWMutex // tier 1
- }
-
- // NewWhoWasList returns a new WhoWasList
- func (list *WhoWasList) Initialize(size int) {
- list.buffer = make([]WhoWas, size)
- list.start = -1
- list.end = -1
- }
-
- // Append adds an entry to the WhoWasList.
- func (list *WhoWasList) Append(whowas WhoWas) {
- list.accessMutex.Lock()
- defer list.accessMutex.Unlock()
-
- if len(list.buffer) == 0 {
- return
- }
-
- var pos int
- if list.start == -1 { // empty
- pos = 0
- list.start = 0
- list.end = 1
- } else if list.start != list.end { // partially full
- pos = list.end
- list.end = (list.end + 1) % len(list.buffer)
- } else if list.start == list.end { // full
- pos = list.end
- list.end = (list.end + 1) % len(list.buffer)
- list.start = list.end // advance start as well, overwriting first entry
- }
-
- list.buffer[pos] = whowas
- }
-
- // Find tries to find an entry in our WhoWasList with the given details.
- func (list *WhoWasList) Find(nickname string, limit int) (results []WhoWas) {
- casefoldedNickname, err := CasefoldName(nickname)
- if err != nil {
- return
- }
-
- list.accessMutex.RLock()
- defer list.accessMutex.RUnlock()
-
- if list.start == -1 {
- return
- }
- // iterate backwards through the ring buffer
- pos := list.prev(list.end)
- for limit == 0 || len(results) < limit {
- if casefoldedNickname == list.buffer[pos].nickCasefolded {
- results = append(results, list.buffer[pos])
- }
- if pos == list.start {
- break
- }
- pos = list.prev(pos)
- }
-
- return
- }
-
- func (list *WhoWasList) prev(index int) int {
- switch index {
- case 0:
- return len(list.buffer) - 1
- default:
- return index - 1
- }
- }
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