datasource: Move datasources into their own packages.

datasource/configdrive/configdrive.go

@@ -0,0 +1,69 @@
+package configdrive
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+const (
+	ec2ApiVersion       = "2009-04-04"
+	openstackApiVersion = "latest"
+)
+
+type configDrive struct {
+	root     string
+	readFile func(filename string) ([]byte, error)
+}
+
+func NewDatasource(root string) *configDrive {
+	return &configDrive{path.Join(root, "openstack"), ioutil.ReadFile}
+}
+
+func (cd *configDrive) IsAvailable() bool {
+	_, err := os.Stat(cd.root)
+	return !os.IsNotExist(err)
+}
+
+func (cd *configDrive) AvailabilityChanges() bool {
+	return true
+}
+
+func (cd *configDrive) ConfigRoot() string {
+	return cd.openstackRoot()
+}
+
+// FetchMetadata attempts to retrieve metadata from ec2/2009-04-04/meta_data.json.
+func (cd *configDrive) FetchMetadata() ([]byte, error) {
+	return cd.tryReadFile(path.Join(cd.ec2Root(), "meta_data.json"))
+}
+
+// FetchUserdata attempts to retrieve the userdata from ec2/2009-04-04/user_data.
+// If no data is found, it will attempt to read from openstack/latest/user_data.
+func (cd *configDrive) FetchUserdata() ([]byte, error) {
+	bytes, err := cd.tryReadFile(path.Join(cd.ec2Root(), "user_data"))
+	if bytes == nil && err == nil {
+		bytes, err = cd.tryReadFile(path.Join(cd.openstackRoot(), "user_data"))
+	}
+	return bytes, err
+}
+
+func (cd *configDrive) Type() string {
+	return "cloud-drive"
+}
+
+func (cd *configDrive) ec2Root() string {
+	return path.Join(cd.root, "ec2", ec2ApiVersion)
+}
+
+func (cd *configDrive) openstackRoot() string {
+	return path.Join(cd.root, "openstack", openstackApiVersion)
+}
+
+func (cd *configDrive) tryReadFile(filename string) ([]byte, error) {
+	data, err := cd.readFile(filename)
+	if os.IsNotExist(err) {
+		err = nil
+	}
+	return data, err
+}