vendor: github.com/moby/buildkit v0.12.0

full diff: https://github.com/moby/buildkit/compare/20230620112432...v0.12.0

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/Microsoft/hcsshim/internal/queue/mq.go

@@ -0,0 +1,92 @@
+package queue
+
+import (
+	"errors"
+	"sync"
+)
+
+var ErrQueueClosed = errors.New("the queue is closed for reading and writing")
+
+// MessageQueue represents a threadsafe message queue to be used to retrieve or
+// write messages to.
+type MessageQueue struct {
+	m        *sync.RWMutex
+	c        *sync.Cond
+	messages []interface{}
+	closed   bool
+}
+
+// NewMessageQueue returns a new MessageQueue.
+func NewMessageQueue() *MessageQueue {
+	m := &sync.RWMutex{}
+	return &MessageQueue{
+		m:        m,
+		c:        sync.NewCond(m),
+		messages: []interface{}{},
+	}
+}
+
+// Enqueue writes `msg` to the queue.
+func (mq *MessageQueue) Enqueue(msg interface{}) error {
+	mq.m.Lock()
+	defer mq.m.Unlock()
+
+	if mq.closed {
+		return ErrQueueClosed
+	}
+	mq.messages = append(mq.messages, msg)
+	// Signal a waiter that there is now a value available in the queue.
+	mq.c.Signal()
+	return nil
+}
+
+// Dequeue will read a value from the queue and remove it. If the queue
+// is empty, this will block until the queue is closed or a value gets enqueued.
+func (mq *MessageQueue) Dequeue() (interface{}, error) {
+	mq.m.Lock()
+	defer mq.m.Unlock()
+
+	for !mq.closed && mq.size() == 0 {
+		mq.c.Wait()
+	}
+
+	// We got woken up, check if it's because the queue got closed.
+	if mq.closed {
+		return nil, ErrQueueClosed
+	}
+
+	val := mq.messages[0]
+	mq.messages[0] = nil
+	mq.messages = mq.messages[1:]
+	return val, nil
+}
+
+// Size returns the size of the queue.
+func (mq *MessageQueue) Size() int {
+	mq.m.RLock()
+	defer mq.m.RUnlock()
+	return mq.size()
+}
+
+// Nonexported size check to check if the queue is empty inside already locked functions.
+func (mq *MessageQueue) size() int {
+	return len(mq.messages)
+}
+
+// Close closes the queue for future writes or reads. Any attempts to read or write from the
+// queue after close will return ErrQueueClosed. This is safe to call multiple times.
+func (mq *MessageQueue) Close() {
+	mq.m.Lock()
+	defer mq.m.Unlock()
+
+	// Already closed, noop
+	if mq.closed {
+		return
+	}
+
+	mq.messages = nil
+	mq.closed = true
+	// If there's anybody currently waiting on a value from Dequeue, we need to
+	// broadcast so the read(s) can return ErrQueueClosed.
+	mq.c.Broadcast()
+}