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package client
import (
"errors"
"sync"
"sync/atomic"
)
// queue A concurrent queue.
type queue[T any] struct {
lock sync.Mutex
cond *sync.Cond
items []T
bufferSize int
stopSignal chan struct{}
isClosed atomic.Bool
}
var (
queueIsFullErr = errors.New("Queue is full")
queueIsClosedErr = errors.New("Queue is closed")
)
// newQueue creates a new queue with the specified buffer size.
func newQueue[T any](bufferSize int) *queue[T] {
q := &queue[T]{
bufferSize: bufferSize,
items: make([]T, 0),
stopSignal: make(chan struct{}),
}
q.cond = sync.NewCond(&q.lock)
return q
}
// push Adds a new item to the queue and returns an error if the queue
// is full.
func (q *queue[T]) push(item T) error {
if q.isClosed.Load() {
return queueIsClosedErr
}
q.lock.Lock()
defer q.lock.Unlock()
if len(q.items) >= q.bufferSize {
return queueIsFullErr
}
q.items = append(q.items, item)
q.cond.Signal()
return nil
}
// pop waits for and removes the first element from the queue, then returns it.
func (q *queue[T]) pop() (T, bool) {
var t T
if q.isClosed.Load() {
return t, false
}
q.lock.Lock()
defer q.lock.Unlock()
// Wait for an item to be available or for a stop signal.
// This ensures that the waiting stops once the queue is cleared.
for len(q.items) == 0 {
select {
case <-q.stopSignal:
return t, false
default:
q.cond.Wait()
}
}
item := q.items[0]
q.items = q.items[1:]
return item, true
}
// clear Clears all elements from the queue.
func (q *queue[T]) clear() {
if !q.isClosed.CompareAndSwap(false, true) {
return
}
q.lock.Lock()
defer q.lock.Unlock()
close(q.stopSignal)
q.items = nil
q.cond.Broadcast()
}
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