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ergo/irc/whowas.go
2018-07-16 03:46:40 -04:00

105 lines
2.2 KiB
Go

// 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
}
// WhoWas is an entry in the WhoWasList.
type WhoWas struct {
nicknameCasefolded string
nickname string
username string
hostname string
realname string
}
// NewWhoWasList returns a new WhoWasList
func NewWhoWasList(size int) *WhoWasList {
return &WhoWasList{
buffer: make([]WhoWas, size),
start: -1,
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].nicknameCasefolded {
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
}
}