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resource.go
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resource.go
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package continuity
import (
"errors"
"fmt"
"os"
"reflect"
"sort"
pb "github.com/containerd/continuity/proto"
"github.com/opencontainers/go-digest"
)
// TODO(stevvooe): A record based model, somewhat sketched out at the bottom
// of this file, will be more flexible. Another possibly is to tie the package
// interface directly to the protobuf type. This will have efficiency
// advantages at the cost coupling the nasty codegen types to the exported
// interface.
type Resource interface {
// Path provides the primary resource path relative to the bundle root. In
// cases where resources have more than one path, such as with hard links,
// this will return the primary path, which is often just the first entry.
Path() string
// Mode returns the
Mode() os.FileMode
UID() int64
GID() int64
}
// ByPath provides the canonical sort order for a set of resources. Use with
// sort.Stable for deterministic sorting.
type ByPath []Resource
func (bp ByPath) Len() int { return len(bp) }
func (bp ByPath) Swap(i, j int) { bp[i], bp[j] = bp[j], bp[i] }
func (bp ByPath) Less(i, j int) bool { return bp[i].Path() < bp[j].Path() }
type XAttrer interface {
XAttrs() map[string][]byte
}
// Hardlinkable is an interface that a resource type satisfies if it can be a
// hardlink target.
type Hardlinkable interface {
// Paths returns all paths of the resource, including the primary path
// returned by Resource.Path. If len(Paths()) > 1, the resource is a hard
// link.
Paths() []string
}
type RegularFile interface {
Resource
XAttrer
Hardlinkable
Size() int64
Digests() []digest.Digest
}
// Merge two or more Resources into new file. Typically, this should be
// used to merge regular files as hardlinks. If the files are not identical,
// other than Paths and Digests, the merge will fail and an error will be
// returned.
func Merge(fs ...Resource) (Resource, error) {
if len(fs) < 1 {
return nil, fmt.Errorf("please provide a resource to merge")
}
if len(fs) == 1 {
return fs[0], nil
}
var paths []string
var digests []digest.Digest
bypath := map[string][]Resource{}
// The attributes are all compared against the first to make sure they
// agree before adding to the above collections. If any of these don't
// correctly validate, the merge fails.
prototype := fs[0]
xattrs := make(map[string][]byte)
// initialize xattrs for use below. All files must have same xattrs.
if prototypeXAttrer, ok := prototype.(XAttrer); ok {
for attr, value := range prototypeXAttrer.XAttrs() {
xattrs[attr] = value
}
}
for _, f := range fs {
h, isHardlinkable := f.(Hardlinkable)
if !isHardlinkable {
return nil, errNotAHardLink
}
if f.Mode() != prototype.Mode() {
return nil, fmt.Errorf("modes do not match: %v != %v", f.Mode(), prototype.Mode())
}
if f.UID() != prototype.UID() {
return nil, fmt.Errorf("uid does not match: %v != %v", f.UID(), prototype.UID())
}
if f.GID() != prototype.GID() {
return nil, fmt.Errorf("gid does not match: %v != %v", f.GID(), prototype.GID())
}
if xattrer, ok := f.(XAttrer); ok {
fxattrs := xattrer.XAttrs()
if !reflect.DeepEqual(fxattrs, xattrs) {
return nil, fmt.Errorf("resource %q xattrs do not match: %v != %v", f, fxattrs, xattrs)
}
}
for _, p := range h.Paths() {
pfs, ok := bypath[p]
if !ok {
// ensure paths are unique by only appending on a new path.
paths = append(paths, p)
}
bypath[p] = append(pfs, f)
}
if regFile, isRegFile := f.(RegularFile); isRegFile {
prototypeRegFile, prototypeIsRegFile := prototype.(RegularFile)
if !prototypeIsRegFile {
return nil, errors.New("prototype is not a regular file")
}
if regFile.Size() != prototypeRegFile.Size() {
return nil, fmt.Errorf("size does not match: %v != %v", regFile.Size(), prototypeRegFile.Size())
}
digests = append(digests, regFile.Digests()...)
} else if device, isDevice := f.(Device); isDevice {
prototypeDevice, prototypeIsDevice := prototype.(Device)
if !prototypeIsDevice {
return nil, errors.New("prototype is not a device")
}
if device.Major() != prototypeDevice.Major() {
return nil, fmt.Errorf("major number does not match: %v != %v", device.Major(), prototypeDevice.Major())
}
if device.Minor() != prototypeDevice.Minor() {
return nil, fmt.Errorf("minor number does not match: %v != %v", device.Minor(), prototypeDevice.Minor())
}
} else if _, isNamedPipe := f.(NamedPipe); isNamedPipe {
_, prototypeIsNamedPipe := prototype.(NamedPipe)
if !prototypeIsNamedPipe {
return nil, errors.New("prototype is not a named pipe")
}
} else {
return nil, errNotAHardLink
}
}
sort.Stable(sort.StringSlice(paths))
// Choose a "canonical" file. Really, it is just the first file to sort
// against. We also effectively select the very first digest as the
// "canonical" one for this file.
first := bypath[paths[0]][0]
resource := resource{
paths: paths,
mode: first.Mode(),
uid: first.UID(),
gid: first.GID(),
xattrs: xattrs,
}
switch typedF := first.(type) {
case RegularFile:
var err error
digests, err = uniqifyDigests(digests...)
if err != nil {
return nil, err
}
return ®ularFile{
resource: resource,
size: typedF.Size(),
digests: digests,
}, nil
case Device:
return &device{
resource: resource,
major: typedF.Major(),
minor: typedF.Minor(),
}, nil
case NamedPipe:
return &namedPipe{
resource: resource,
}, nil
default:
return nil, errNotAHardLink
}
}
type Directory interface {
Resource
XAttrer
// Directory is a no-op method to identify directory objects by interface.
Directory()
}
type SymLink interface {
Resource
// Target returns the target of the symlink contained in the .
Target() string
}
type NamedPipe interface {
Resource
Hardlinkable
XAttrer
// Pipe is a no-op method to allow consistent resolution of NamedPipe
// interface.
Pipe()
}
type Device interface {
Resource
Hardlinkable
XAttrer
Major() uint64
Minor() uint64
}
type resource struct {
paths []string
mode os.FileMode
uid, gid int64
xattrs map[string][]byte
}
var _ Resource = &resource{}
func (r *resource) Path() string {
if len(r.paths) < 1 {
return ""
}
return r.paths[0]
}
func (r *resource) Mode() os.FileMode {
return r.mode
}
func (r *resource) UID() int64 {
return r.uid
}
func (r *resource) GID() int64 {
return r.gid
}
type regularFile struct {
resource
size int64
digests []digest.Digest
}
var _ RegularFile = ®ularFile{}
// newRegularFile returns the RegularFile, using the populated base resource
// and one or more digests of the content.
func newRegularFile(base resource, paths []string, size int64, dgsts ...digest.Digest) (RegularFile, error) {
if !base.Mode().IsRegular() {
return nil, fmt.Errorf("not a regular file")
}
base.paths = make([]string, len(paths))
copy(base.paths, paths)
// make our own copy of digests
ds := make([]digest.Digest, len(dgsts))
copy(ds, dgsts)
return ®ularFile{
resource: base,
size: size,
digests: ds,
}, nil
}
func (rf *regularFile) Paths() []string {
paths := make([]string, len(rf.paths))
copy(paths, rf.paths)
return paths
}
func (rf *regularFile) Size() int64 {
return rf.size
}
func (rf *regularFile) Digests() []digest.Digest {
digests := make([]digest.Digest, len(rf.digests))
copy(digests, rf.digests)
return digests
}
func (rf *regularFile) XAttrs() map[string][]byte {
xattrs := make(map[string][]byte, len(rf.xattrs))
for attr, value := range rf.xattrs {
xattrs[attr] = append(xattrs[attr], value...)
}
return xattrs
}
type directory struct {
resource
}
var _ Directory = &directory{}
func newDirectory(base resource) (Directory, error) {
if !base.Mode().IsDir() {
return nil, fmt.Errorf("not a directory")
}
return &directory{
resource: base,
}, nil
}
func (d *directory) Directory() {}
func (d *directory) XAttrs() map[string][]byte {
xattrs := make(map[string][]byte, len(d.xattrs))
for attr, value := range d.xattrs {
xattrs[attr] = append(xattrs[attr], value...)
}
return xattrs
}
type symLink struct {
resource
target string
}
var _ SymLink = &symLink{}
func newSymLink(base resource, target string) (SymLink, error) {
if base.Mode()&os.ModeSymlink == 0 {
return nil, fmt.Errorf("not a symlink")
}
return &symLink{
resource: base,
target: target,
}, nil
}
func (l *symLink) Target() string {
return l.target
}
type namedPipe struct {
resource
}
var _ NamedPipe = &namedPipe{}
func newNamedPipe(base resource, paths []string) (NamedPipe, error) {
if base.Mode()&os.ModeNamedPipe == 0 {
return nil, fmt.Errorf("not a namedpipe")
}
base.paths = make([]string, len(paths))
copy(base.paths, paths)
return &namedPipe{
resource: base,
}, nil
}
func (np *namedPipe) Pipe() {}
func (np *namedPipe) Paths() []string {
paths := make([]string, len(np.paths))
copy(paths, np.paths)
return paths
}
func (np *namedPipe) XAttrs() map[string][]byte {
xattrs := make(map[string][]byte, len(np.xattrs))
for attr, value := range np.xattrs {
xattrs[attr] = append(xattrs[attr], value...)
}
return xattrs
}
type device struct {
resource
major, minor uint64
}
var _ Device = &device{}
func newDevice(base resource, paths []string, major, minor uint64) (Device, error) {
if base.Mode()&os.ModeDevice == 0 {
return nil, fmt.Errorf("not a device")
}
base.paths = make([]string, len(paths))
copy(base.paths, paths)
return &device{
resource: base,
major: major,
minor: minor,
}, nil
}
func (d *device) Paths() []string {
paths := make([]string, len(d.paths))
copy(paths, d.paths)
return paths
}
func (d *device) XAttrs() map[string][]byte {
xattrs := make(map[string][]byte, len(d.xattrs))
for attr, value := range d.xattrs {
xattrs[attr] = append(xattrs[attr], value...)
}
return xattrs
}
func (d device) Major() uint64 {
return d.major
}
func (d device) Minor() uint64 {
return d.minor
}
// toProto converts a resource to a protobuf record. We'd like to push this
// the individual types but we want to keep this all together during
// prototyping.
func toProto(resource Resource) *pb.Resource {
b := &pb.Resource{
Path: []string{resource.Path()},
Mode: uint32(resource.Mode()),
Uid: resource.UID(),
Gid: resource.GID(),
}
if xattrer, ok := resource.(XAttrer); ok {
// Sorts the XAttrs by name for consistent ordering.
keys := []string{}
xattrs := xattrer.XAttrs()
for k := range xattrs {
keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
b.Xattr = append(b.Xattr, &pb.XAttr{Name: k, Data: xattrs[k]})
}
}
switch r := resource.(type) {
case RegularFile:
b.Path = r.Paths()
b.Size = uint64(r.Size())
for _, dgst := range r.Digests() {
b.Digest = append(b.Digest, dgst.String())
}
case SymLink:
b.Target = r.Target()
case Device:
b.Major, b.Minor = r.Major(), r.Minor()
b.Path = r.Paths()
case NamedPipe:
b.Path = r.Paths()
}
// enforce a few stability guarantees that may not be provided by the
// resource implementation.
sort.Strings(b.Path)
return b
}
// fromProto converts from a protobuf Resource to a Resource interface.
func fromProto(b *pb.Resource) (Resource, error) {
base := &resource{
paths: b.Path,
mode: os.FileMode(b.Mode),
uid: b.Uid,
gid: b.Gid,
}
base.xattrs = make(map[string][]byte, len(b.Xattr))
for _, attr := range b.Xattr {
base.xattrs[attr.Name] = attr.Data
}
switch {
case base.Mode().IsRegular():
dgsts := make([]digest.Digest, len(b.Digest))
for i, dgst := range b.Digest {
// TODO(stevvooe): Should we be validating at this point?
dgsts[i] = digest.Digest(dgst)
}
return newRegularFile(*base, b.Path, int64(b.Size), dgsts...)
case base.Mode().IsDir():
return newDirectory(*base)
case base.Mode()&os.ModeSymlink != 0:
return newSymLink(*base, b.Target)
case base.Mode()&os.ModeNamedPipe != 0:
return newNamedPipe(*base, b.Path)
case base.Mode()&os.ModeDevice != 0:
return newDevice(*base, b.Path, b.Major, b.Minor)
}
return nil, fmt.Errorf("unknown resource record (%#v): %s", b, base.Mode())
}
// NOTE(stevvooe): An alternative model that supports inline declaration.
// Convenient for unit testing where inline declarations may be desirable but
// creates an awkward API for the standard use case.
// type ResourceKind int
// const (
// ResourceRegularFile = iota + 1
// ResourceDirectory
// ResourceSymLink
// Resource
// )
// type Resource struct {
// Kind ResourceKind
// Paths []string
// Mode os.FileMode
// UID string
// GID string
// Size int64
// Digests []digest.Digest
// Target string
// Major, Minor int
// XAttrs map[string][]byte
// }
// type RegularFile struct {
// Paths []string
// Size int64
// Digests []digest.Digest
// Perm os.FileMode // os.ModePerm + sticky, setuid, setgid
// }