queue.go

Documentation: golang.org/x/net/internal/quic

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build go1.21
     6  
     7  package quic
     8  
     9  import "context"
    10  
    11  // A queue is an unbounded queue of some item (new connections and streams).
    12  type queue[T any] struct {
    13  	// The gate condition is set if the queue is non-empty or closed.
    14  	gate gate
    15  	err  error
    16  	q    []T
    17  }
    18  
    19  func newQueue[T any]() queue[T] {
    20  	return queue[T]{gate: newGate()}
    21  }
    22  
    23  // close closes the queue, causing pending and future pop operations
    24  // to return immediately with err.
    25  func (q *queue[T]) close(err error) {
    26  	q.gate.lock()
    27  	defer q.unlock()
    28  	if q.err == nil {
    29  		q.err = err
    30  	}
    31  }
    32  
    33  // put appends an item to the queue.
    34  // It returns true if the item was added, false if the queue is closed.
    35  func (q *queue[T]) put(v T) bool {
    36  	q.gate.lock()
    37  	defer q.unlock()
    38  	if q.err != nil {
    39  		return false
    40  	}
    41  	q.q = append(q.q, v)
    42  	return true
    43  }
    44  
    45  // get removes the first item from the queue, blocking until ctx is done, an item is available,
    46  // or the queue is closed.
    47  func (q *queue[T]) get(ctx context.Context, testHooks connTestHooks) (T, error) {
    48  	var zero T
    49  	if err := q.gate.waitAndLock(ctx, testHooks); err != nil {
    50  		return zero, err
    51  	}
    52  	defer q.unlock()
    53  	if q.err != nil {
    54  		return zero, q.err
    55  	}
    56  	v := q.q[0]
    57  	copy(q.q[:], q.q[1:])
    58  	q.q[len(q.q)-1] = zero
    59  	q.q = q.q[:len(q.q)-1]
    60  	return v, nil
    61  }
    62  
    63  func (q *queue[T]) unlock() {
    64  	q.gate.unlock(q.err != nil || len(q.q) > 0)
    65  }
    66
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