1 files changed, 111 insertions, 0 deletions
diff --git a/vendor/github.com/Microsoft/hcsshim/internal/queue/mq.go b/vendor/github.com/Microsoft/hcsshim/internal/queue/mq.go
new file mode 100644
index 000000000..e177c9a62
--- /dev/null
+++ b/vendor/github.com/Microsoft/hcsshim/internal/queue/mq.go
@@ -0,0 +1,111 @@
+package queue
+
+import (
+	"errors"
+	"sync"
+)
+
+var (
+	ErrQueueClosed = errors.New("the queue is closed for reading and writing")
+	ErrQueueEmpty  = errors.New("the queue is empty")
+)
+
+// 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{}{},
+	}
+}
+
+// Write writes `msg` to the queue.
+func (mq *MessageQueue) Write(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
+}
+
+// Read will read a value from the queue if available, otherwise return an error.
+func (mq *MessageQueue) Read() (interface{}, error) {
+	mq.m.Lock()
+	defer mq.m.Unlock()
+	if mq.closed {
+		return nil, ErrQueueClosed
+	}
+	if mq.isEmpty() {
+		return nil, ErrQueueEmpty
+	}
+	val := mq.messages[0]
+	mq.messages[0] = nil
+	mq.messages = mq.messages[1:]
+	return val, nil
+}
+
+// ReadOrWait will read a value from the queue if available, else it will wait for a
+// value to become available. This will block forever if nothing gets written or until
+// the queue gets closed.
+func (mq *MessageQueue) ReadOrWait() (interface{}, error) {
+	mq.m.Lock()
+	if mq.closed {
+		mq.m.Unlock()
+		return nil, ErrQueueClosed
+	}
+	if mq.isEmpty() {
+		for !mq.closed && mq.isEmpty() {
+			mq.c.Wait()
+		}
+		mq.m.Unlock()
+		return mq.Read()
+	}
+	val := mq.messages[0]
+	mq.messages[0] = nil
+	mq.messages = mq.messages[1:]
+	mq.m.Unlock()
+	return val, nil
+}
+
+// IsEmpty returns if the queue is empty
+func (mq *MessageQueue) IsEmpty() bool {
+	mq.m.RLock()
+	defer mq.m.RUnlock()
+	return len(mq.messages) == 0
+}
+
+// Nonexported empty check that doesn't lock so we can call this in Read and Write.
+func (mq *MessageQueue) isEmpty() bool {
+	return len(mq.messages) == 0
+}
+
+// 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
+	if mq.closed {
+		return
+	}
+	mq.messages = nil
+	mq.closed = true
+	// If there's anybody currently waiting on a value from ReadOrWait, we need to
+	// broadcast so the read(s) can return ErrQueueClosed.
+	mq.c.Broadcast()
+}