57_Wolve
03a47deade
Create Release & Upload Assets / Upload Assets To Gitea w/ goreleaser (push) Failing after 11s
114 lines
2.6 KiB
Go
114 lines
2.6 KiB
Go
// Created by Yaz Saito on 06/15/12.
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// Modified by Geert-Johan Riemer, Foize B.V.
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// TODO:
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// - travis CI
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// - maybe add method (*Queue).Peek()
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package fifo
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import (
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"sync"
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)
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const chunkSize = 64
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// chunks are used to make a queue auto resizeable.
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type chunk struct {
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items [chunkSize]interface{} // list of queue'ed items
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first, last int // positions for the first and list item in this chunk
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next *chunk // pointer to the next chunk (if any)
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}
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// fifo queue
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type Queue struct {
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head, tail *chunk // chunk head and tail
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count int // total amount of items in the queue
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lock sync.Mutex // synchronisation lock
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}
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// NewQueue creates a new and empty *fifo.Queue
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func NewQueue() (q *Queue) {
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initChunk := new(chunk)
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q = &Queue{
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head: initChunk,
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tail: initChunk,
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}
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return q
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}
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// Return the number of items in the queue
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func (q *Queue) Len() (length int) {
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// locking to make Queue thread-safe
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q.lock.Lock()
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defer q.lock.Unlock()
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// copy q.count and return length
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length = q.count
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return length
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}
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// Add an item to the end of the queue
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func (q *Queue) Add(item interface{}) {
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// locking to make Queue thread-safe
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q.lock.Lock()
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defer q.lock.Unlock()
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// check if item is valid
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if item == nil {
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panic("can not add nil item to fifo queue")
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}
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// if the tail chunk is full, create a new one and add it to the queue.
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if q.tail.last >= chunkSize {
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q.tail.next = new(chunk)
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q.tail = q.tail.next
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}
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// add item to the tail chunk at the last position
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q.tail.items[q.tail.last] = item
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q.tail.last++
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q.count++
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}
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// Remove the item at the head of the queue and return it.
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// Returns nil when there are no items left in queue.
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func (q *Queue) Next() (item interface{}) {
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// locking to make Queue thread-safe
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q.lock.Lock()
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defer q.lock.Unlock()
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// Return nil if there are no items to return
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if q.count == 0 {
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return nil
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}
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// FIXME: why would this check be required?
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if q.head.first >= q.head.last {
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return nil
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}
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// Get item from queue
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item = q.head.items[q.head.first]
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// increment first position and decrement queue item count
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q.head.first++
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q.count--
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if q.head.first >= q.head.last {
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// we're at the end of this chunk and we should do some maintainance
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// if there are no follow up chunks then reset the current one so it can be used again.
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if q.count == 0 {
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q.head.first = 0
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q.head.last = 0
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q.head.next = nil
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} else {
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// set queue's head chunk to the next chunk
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// old head will fall out of scope and be GC-ed
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q.head = q.head.next
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}
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}
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// return the retrieved item
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return item
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}
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