/usr/share/gocode/src/gopkg.in/eapache/queue.v1/queue.go is in golang-gopkg-eapache-queue.v1-dev 1.0.2-4.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 | /*
Package queue provides a fast, ring-buffer queue based on the version suggested by Dariusz Górecki.
Using this instead of other, simpler, queue implementations (slice+append or linked list) provides
substantial memory and time benefits, and fewer GC pauses.
The queue implemented here is as fast as it is for an additional reason: it is *not* thread-safe.
*/
package queue
const minQueueLen = 16
// Queue represents a single instance of the queue data structure.
type Queue struct {
buf []interface{}
head, tail, count int
}
// New constructs and returns a new Queue.
func New() *Queue {
return &Queue{
buf: make([]interface{}, minQueueLen),
}
}
// Length returns the number of elements currently stored in the queue.
func (q *Queue) Length() int {
return q.count
}
// resizes the queue to fit exactly twice its current contents
// this can result in shrinking if the queue is less than half-full
func (q *Queue) resize() {
newBuf := make([]interface{}, q.count*2)
if q.tail > q.head {
copy(newBuf, q.buf[q.head:q.tail])
} else {
n := copy(newBuf, q.buf[q.head:])
copy(newBuf[n:], q.buf[:q.tail])
}
q.head = 0
q.tail = q.count
q.buf = newBuf
}
// Add puts an element on the end of the queue.
func (q *Queue) Add(elem interface{}) {
if q.count == len(q.buf) {
q.resize()
}
q.buf[q.tail] = elem
q.tail = (q.tail + 1) % len(q.buf)
q.count++
}
// Peek returns the element at the head of the queue. This call panics
// if the queue is empty.
func (q *Queue) Peek() interface{} {
if q.count <= 0 {
panic("queue: Peek() called on empty queue")
}
return q.buf[q.head]
}
// Get returns the element at index i in the queue. If the index is
// invalid, the call will panic.
func (q *Queue) Get(i int) interface{} {
if i < 0 || i >= q.count {
panic("queue: Get() called with index out of range")
}
return q.buf[(q.head+i)%len(q.buf)]
}
// Remove removes the element from the front of the queue. If you actually
// want the element, call Peek first. This call panics if the queue is empty.
func (q *Queue) Remove() {
if q.count <= 0 {
panic("queue: Remove() called on empty queue")
}
q.buf[q.head] = nil
q.head = (q.head + 1) % len(q.buf)
q.count--
if len(q.buf) > minQueueLen && q.count*4 == len(q.buf) {
q.resize()
}
}
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