Initial

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/github.com/Microsoft/hcsshim/internal/wclayer/preparelayer.go

@@ -0,0 +1,47 @@
+package wclayer
+
+import (
+	"sync"
+
+	"github.com/Microsoft/hcsshim/internal/hcserror"
+	"github.com/sirupsen/logrus"
+)
+
+var prepareLayerLock sync.Mutex
+
+// PrepareLayer finds a mounted read-write layer matching path and enables the
+// the filesystem filter for use on that layer.  This requires the paths to all
+// parent layers, and is necessary in order to view or interact with the layer
+// as an actual filesystem (reading and writing files, creating directories, etc).
+// Disabling the filter must be done via UnprepareLayer.
+func PrepareLayer(path string, parentLayerPaths []string) (err error) {
+	title := "hcsshim::PrepareLayer"
+	fields := logrus.Fields{
+		"path": path,
+	}
+	logrus.WithFields(fields).Debug(title)
+	defer func() {
+		if err != nil {
+			fields[logrus.ErrorKey] = err
+			logrus.WithFields(fields).Error(err)
+		} else {
+			logrus.WithFields(fields).Debug(title + " - succeeded")
+		}
+	}()
+
+	// Generate layer descriptors
+	layers, err := layerPathsToDescriptors(parentLayerPaths)
+	if err != nil {
+		return err
+	}
+
+	// This lock is a temporary workaround for a Windows bug. Only allowing one
+	// call to prepareLayer at a time vastly reduces the chance of a timeout.
+	prepareLayerLock.Lock()
+	defer prepareLayerLock.Unlock()
+	err = prepareLayer(&stdDriverInfo, path, layers)
+	if err != nil {
+		return hcserror.New(err, title+" - failed", "")
+	}
+	return nil
+}