cleanup: move pkg/ to internal/

The internal/ directory in Go has a special meaning, and indicates that
those packages are not meant for external consumption. Ceph-CSI does
provide public APIs for other projects to consume. There is no plan to
keep the API of the internally used packages stable.

Closes: #903
Signed-off-by: Niels de Vos <ndevos@redhat.com>

internal/util/volid.go

@@ -0,0 +1,151 @@
+/*
+Copyright 2019 Ceph-CSI authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"strings"
+)
+
+/*
+CSIIdentifier contains the elements that form a CSI ID to be returned by the CSI plugin, and
+contains enough information to decompose and extract required cluster and pool information to locate
+the volume that relates to the CSI ID.
+
+The CSI identifier is composed as elaborated in the comment against ComposeCSIID and thus,
+DecomposeCSIID is the inverse of the same function.
+
+The CSIIdentifier structure carries the following fields,
+- LocationID: 64 bit integer identifier determining the location of the volume on the Ceph cluster.
+  It is the ID of the poolname or fsname, for RBD or CephFS backed volumes respectively.
+- EncodingVersion: Carries the version number of the encoding scheme used to encode the CSI ID,
+  and is preserved for any future proofing w.r.t changes in the encoding scheme, and to retain
+  ability to parse backward compatible encodings.
+- ClusterID: Is a unique ID per cluster that the CSI instance is serving and is restricted to
+  lengths that can be accommodated in the encoding scheme.
+- ObjectUUID: Is the on-disk uuid of the object (image/snapshot) name, for the CSI volume that
+  corresponds to this CSI ID.
+*/
+type CSIIdentifier struct {
+	LocationID      int64
+	EncodingVersion uint16
+	ClusterID       string
+	ObjectUUID      string
+}
+
+// This maximum comes from the CSI spec on max bytes allowed in the various CSI ID fields
+const maxVolIDLen = 128
+
+/*
+ComposeCSIID composes a CSI ID from passed in parameters.
+Version 1 of the encoding scheme is as follows,
+	[csi_id_version=1:4byte] + [-:1byte]
+	[length of clusterID=1:4byte] + [-:1byte]
+	[clusterID:36bytes (MAX)] + [-:1byte]
+	[poolID:16bytes] + [-:1byte]
+	[ObjectUUID:36bytes]
+
+	Total of constant field lengths, including '-' field separators would hence be,
+	4+1+4+1+1+16+1+36 = 64
+*/
+const (
+	knownFieldSize = 64
+	uuidSize       = 36
+)
+
+func (ci CSIIdentifier) ComposeCSIID() (string, error) {
+	buf16 := make([]byte, 2)
+	buf64 := make([]byte, 8)
+
+	if (knownFieldSize + len(ci.ClusterID)) > maxVolIDLen {
+		return "", errors.New("CSI ID encoding length overflow")
+	}
+
+	if len(ci.ObjectUUID) != uuidSize {
+		return "", errors.New("CSI ID invalid object uuid")
+	}
+
+	binary.BigEndian.PutUint16(buf16, ci.EncodingVersion)
+	versionEncodedHex := hex.EncodeToString(buf16)
+
+	binary.BigEndian.PutUint16(buf16, uint16(len(ci.ClusterID)))
+	clusterIDLength := hex.EncodeToString(buf16)
+
+	binary.BigEndian.PutUint64(buf64, uint64(ci.LocationID))
+	poolIDEncodedHex := hex.EncodeToString(buf64)
+
+	return strings.Join([]string{versionEncodedHex, clusterIDLength, ci.ClusterID,
+		poolIDEncodedHex, ci.ObjectUUID}, "-"), nil
+}
+
+/*
+DecomposeCSIID composes a CSIIdentifier from passed in string
+*/
+func (ci *CSIIdentifier) DecomposeCSIID(composedCSIID string) (err error) {
+	bytesToProcess := uint16(len(composedCSIID))
+
+	// if length is less that expected constant elements, then bail out!
+	if bytesToProcess < knownFieldSize {
+		return errors.New("failed to decode CSI identifier, string underflow")
+	}
+
+	buf16, err := hex.DecodeString(composedCSIID[0:4])
+	if err != nil {
+		return err
+	}
+	ci.EncodingVersion = binary.BigEndian.Uint16(buf16)
+	// 4 for version encoding and 1 for '-' separator
+	bytesToProcess -= 5
+
+	buf16, err = hex.DecodeString(composedCSIID[5:9])
+	if err != nil {
+		return err
+	}
+	clusterIDLength := binary.BigEndian.Uint16(buf16)
+	// 4 for length encoding and 1 for '-' separator
+	bytesToProcess -= 5
+
+	if bytesToProcess < (clusterIDLength + 1) {
+		return errors.New("failed to decode CSI identifier, string underflow")
+	}
+	ci.ClusterID = composedCSIID[10 : 10+clusterIDLength]
+	// additional 1 for '-' separator
+	bytesToProcess -= (clusterIDLength + 1)
+	nextFieldStartIdx := 10 + clusterIDLength + 1
+
+	if bytesToProcess < 17 {
+		return errors.New("failed to decode CSI identifier, string underflow")
+	}
+	buf64, err := hex.DecodeString(composedCSIID[nextFieldStartIdx : nextFieldStartIdx+16])
+	if err != nil {
+		return err
+	}
+	ci.LocationID = int64(binary.BigEndian.Uint64(buf64))
+	// 16 for poolID encoding and 1 for '-' separator
+	bytesToProcess -= 17
+	nextFieldStartIdx += 17
+
+	// has to be an exact match
+	if bytesToProcess != uuidSize {
+		return errors.New("failed to decode CSI identifier, string size mismatch")
+	}
+	ci.ObjectUUID = composedCSIID[nextFieldStartIdx : nextFieldStartIdx+uuidSize]
+
+	return err
+}