Update integration test to support windows

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

client_windows_test.go

@@ -0,0 +1,87 @@
+package containerd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/pkg/errors"
+)
+
+const (
+	defaultAddress = `\\.\pipe\containerd-containerd-test`
+	testImage      = "docker.io/library/go:nanoserver"
+)
+
+var (
+	dockerLayerFolders []string
+
+	defaultRoot = filepath.Join(os.Getenv("programfiles"), "containerd", "root-test")
+)
+
+func platformTestSetup(client *Client) error {
+	var (
+		roots       []string
+		layerChains = make(map[string]string)
+	)
+	// Since we can't pull images yet, we'll piggyback on the default
+	// docker's images
+	wfPath := `C:\ProgramData\docker\windowsfilter`
+	wf, err := os.Open(wfPath)
+	if err != nil {
+		return errors.Wrapf(err, "failed to access docker layers @ %s", wfPath)
+	}
+	defer wf.Close()
+	entries, err := wf.Readdirnames(0)
+	if err != nil {
+		return errors.Wrapf(err, "failed to read %s entries", wfPath)
+	}
+
+	for _, fn := range entries {
+		layerChainPath := filepath.Join(wfPath, fn, "layerchain.json")
+		lfi, err := os.Stat(layerChainPath)
+		switch {
+		case err == nil && lfi.Mode().IsRegular():
+			f, err := os.OpenFile(layerChainPath, os.O_RDONLY, 0660)
+			if err != nil {
+				fmt.Fprintln(os.Stderr,
+					errors.Wrapf(err, "failed to open %s", layerChainPath))
+				continue
+			}
+			defer f.Close()
+			l := make([]string, 0)
+			if err := json.NewDecoder(f).Decode(&l); err != nil {
+				fmt.Fprintln(os.Stderr,
+					errors.Wrapf(err, "failed to decode %s", layerChainPath))
+				continue
+			}
+			switch {
+			case len(l) == 1:
+				layerChains[l[0]] = filepath.Join(wfPath, fn)
+			case len(l) > 1:
+				fmt.Fprintf(os.Stderr, "Too many entries in %s: %d", layerChainPath, len(l))
+			case len(l) == 0:
+				roots = append(roots, filepath.Join(wfPath, fn))
+			}
+		case os.IsNotExist(err):
+			// keep on going
+		default:
+			return errors.Wrapf(err, "error trying to access %s", layerChainPath)
+		}
+	}
+
+	// They'll be 2 roots, just take the first one
+	l := roots[0]
+	dockerLayerFolders = append(dockerLayerFolders, l)
+	for {
+		l = layerChains[l]
+		if l == "" {
+			break
+		}
+
+		dockerLayerFolders = append([]string{l}, dockerLayerFolders...)
+	}
+
+	return nil
+}