Implementing backup methods

11 files changed, 692 insertions, 7 deletions

diff --git a/backup/backup.go b/backup/backup.go
new file mode 100644
index 0000000..9c012e0
--- /dev/null
+++ b/backup/backup.go
@@ -0,0 +1,115 @@
+package backup
+
+import (
+	"code.laria.me/petrific/cache"
+	"code.laria.me/petrific/fs"
+	"code.laria.me/petrific/objects"
+	"code.laria.me/petrific/storage"
+	"io"
+	"time"
+)
+
+func WriteDir(
+	store storage.Storage,
+	abspath string,
+	d fs.Dir,
+	pcache cache.Cache,
+) (objects.ObjectId, error) {
+	children, err := d.Readdir()
+	if err != nil {
+		return objects.ObjectId{}, err
+	}
+
+	infos := make(objects.Tree)
+	for _, c := range children {
+		var info objects.TreeEntry
+
+		switch c.Type() {
+		case fs.FFile:
+			mtime, file_id, ok := pcache.PathUpdated(abspath)
+			if !ok || mtime.Before(c.ModTime()) {
+				// According to cache the file was changed
+
+				rwc, err := c.(fs.RegularFile).Open()
+				if err != nil {
+					return objects.ObjectId{}, err
+				}
+
+				file_id, err = WriteFile(store, rwc)
+				rwc.Close()
+				if err != nil {
+					return objects.ObjectId{}, err
+				}
+
+				pcache.SetPathUpdated(abspath+"/"+c.Name(), c.ModTime(), file_id)
+			}
+
+			info = objects.NewTreeEntryFile(file_id, c.Executable())
+		case fs.FDir:
+			subtree_id, err := WriteDir(store, abspath+"/"+c.Name(), c.(fs.Dir), pcache)
+			if err != nil {
+				return objects.ObjectId{}, err
+			}
+
+			info = objects.NewTreeEntryDir(subtree_id, c.Executable())
+		case fs.FSymlink:
+			target, err := c.(fs.Symlink).Readlink()
+			if err != nil {
+				return objects.ObjectId{}, err
+			}
+
+			info = objects.NewTreeEntrySymlink(target, c.Executable())
+		}
+
+		if info != nil {
+			infos[c.Name()] = info
+		}
+	}
+
+	return storage.SetObject(store, objects.ToRawObject(infos))
+}
+
+const BlobChunkSize = 16 * 1024 * 1024 // 16MB
+
+func WriteFile(store storage.Storage, r io.Reader) (objects.ObjectId, error) {
+	// Right now we will create the file as fixed chunks of size BlobChunkSize
+	// It Would be more efficient to use a dynamic/content aware chunking method but this can be added later.
+	// The way files are serialized allows for any chunk size and addition of more properties in the future while staying compatible
+
+	fragments := make(objects.File, 0)
+
+	read_buf := make([]byte, BlobChunkSize)
+	for {
+		n, err := io.ReadFull(r, read_buf)
+		if err == nil || err == io.ErrUnexpectedEOF {
+			content := objects.Blob(read_buf[:n])
+			blob_id, err := storage.SetObject(store, objects.ToRawObject(&content))
+			if err != nil {
+				return objects.ObjectId{}, err
+			}
+
+			fragments = append(fragments, objects.FileFragment{Blob: blob_id, Size: uint64(n)})
+		} else if err == io.EOF {
+			break
+		} else {
+			return objects.ObjectId{}, err
+		}
+	}
+
+	return storage.SetObject(store, objects.ToRawObject(&fragments))
+}
+
+func CreateSnapshot(
+	store storage.Storage,
+	tree_id objects.ObjectId,
+	date time.Time,
+	container string,
+	comment string,
+) (objects.ObjectId, error) {
+	return storage.SetObject(store, objects.ToRawObject(&objects.Snapshot{
+		Tree:      tree_id,
+		Date:      date,
+		Container: container,
+		Comment:   comment,
+	}))
+}
diff --git a/backup/backup_test.go b/backup/backup_test.go
new file mode 100644
index 0000000..2fee26e
--- /dev/null
+++ b/backup/backup_test.go
@@ -0,0 +1,133 @@
+package backup
+
+import (
+	"bytes"
+	"code.laria.me/petrific/cache"
+	"code.laria.me/petrific/fs"
+	"code.laria.me/petrific/objects"
+	"code.laria.me/petrific/storage"
+	"testing"
+)
+
+func wantObject(
+	t *testing.T,
+	s storage.Storage,
+	id_str string,
+	want []byte,
+) {
+	id, err := objects.ParseObjectId(id_str)
+	if err != nil {
+		t.Errorf("Could not parse id: %s", err)
+		return
+	}
+
+	have, err := s.Get(id)
+	if err != nil {
+		t.Errorf("Could not get %s: %s", id, err)
+		return
+	}
+
+	if !bytes.Equal(want, have) {
+		t.Errorf("Wrong result for %s: (size=%d) %#s", id, len(have), have)
+	}
+}
+
+func TestWriteLargeFile(t *testing.T) {
+	s := storage.NewMemoryStorage()
+
+	id, err := WriteFile(s, bytes.NewReader(make([]byte, 2*BlobChunkSize+100)))
+	if err != nil {
+		t.Fatalf("Unexpected error when writing file: %s", err)
+	}
+
+	if id.String() != "sha3-256:ab7907ee6b45b343422a0354de500bcf99f5ff69fe8125be84e43d421803c34e" {
+		t.Errorf("Unexpected file id: %s", id)
+	}
+
+	want_large_blob := append([]byte("blob 16777216\n"), make([]byte, BlobChunkSize)...)
+	want_small_blob := append([]byte("blob 100\n"), make([]byte, 100)...)
+	want_file := []byte("file 274\n" +
+		"blob=sha3-256:7287cbb09bdd8a0d96a6f6297413cd9d09a2763814636245a5a44120e6351be3&size=16777216\n" +
+		"blob=sha3-256:7287cbb09bdd8a0d96a6f6297413cd9d09a2763814636245a5a44120e6351be3&size=16777216\n" +
+		"blob=sha3-256:ddf124464f7b80e95f4a9c704f79e7037ff5d731648ba6b40c769893b428128c&size=100\n")
+
+	wantObject(t, s, "sha3-256:ab7907ee6b45b343422a0354de500bcf99f5ff69fe8125be84e43d421803c34e", want_file)
+	wantObject(t, s, "sha3-256:7287cbb09bdd8a0d96a6f6297413cd9d09a2763814636245a5a44120e6351be3", want_large_blob)
+	wantObject(t, s, "sha3-256:ddf124464f7b80e95f4a9c704f79e7037ff5d731648ba6b40c769893b428128c", want_small_blob)
+}
+
+func mkfile(t *testing.T, d fs.Dir, name string, exec bool, content []byte) {
+	f, err := d.CreateChildFile(name, exec)
+	if err != nil {
+		t.Fatalf("Could not create file %s: %s", name, err)
+	}
+
+	rwc, err := f.Open()
+	if err != nil {
+		t.Fatalf("Could not create file %s: %s", name, err)
+	}
+	defer rwc.Close()
+
+	if _, err := rwc.Write(content); err != nil {
+		t.Fatalf("Could not create file %s: %s", name, err)
+	}
+}
+
+func TestWriteDir(t *testing.T) {
+	s := storage.NewMemoryStorage()
+
+	root := fs.NewMemoryFSRoot("root")
+
+	mkfile(t, root, "foo", false, []byte("foo"))
+	mkfile(t, root, "bar", true, []byte(""))
+	if _, err := root.CreateChildSymlink("baz", "foo"); err != nil {
+		t.Fatalf("Failed creating symlink baz: %s", err)
+	}
+	d, err := root.CreateChildDir("sub")
+	if err != nil {
+		t.Fatalf("Failed creating dir: %s", err)
+	}
+	mkfile(t, d, "a", false, []byte(""))
+	if _, err = d.CreateChildDir("b"); err != nil {
+		t.Fatalf("Failed creating dir: %s", err)
+	}
+
+	id, err := WriteDir(s, "", root, cache.NopCache{})
+	if err != nil {
+		t.Fatalf("Could not WriteDir: %s", err)
+	}
+
+	if id.String() != "sha3-256:09e881f57befa1eacec744e3857a36f0d9d5dd1fa72ba96564b467a3d7d0c0d5" {
+		t.Errorf("Unexpected dir id: %s", id)
+	}
+
+	//4a10682307d5b5dc072d1b862497296640176109347b149aad38cd640000491b
+	obj_emptyfile := []byte("file 0\n")
+
+	//ba632076629ff33238850c870fcb51e4b7b67b3d9dcb66314adbcf1770a5fea7
+	obj_fooblob := []byte("blob 3\nfoo")
+	//fa50ca1fc739852528ecc149b424a8ccbdf84b73c8718cde4525f2a410d79244
+	obj_foofile := []byte("file 86\nblob=sha3-256:ba632076629ff33238850c870fcb51e4b7b67b3d9dcb66314adbcf1770a5fea7&size=3\n")
+
+	//1dc6fae780ae4a1e823a5b8e26266356a2e1d22e5904b0652dcff6e3c0e72067
+	obj_emptytree := []byte("tree 0\n")
+
+	//f1716a1b0cad23b6faab9712243402b8f8e7919c377fc5d5d87bd465cef056d7
+	obj_subdir := []byte("tree 239\n" +
+		"acl=u::rw-,g::r--,o::r--&name=a&ref=sha3-256:4a10682307d5b5dc072d1b862497296640176109347b149aad38cd640000491b&type=file\n" +
+		"acl=u::rwx,g::r-x,o::r-x&name=b&ref=sha3-256:1dc6fae780ae4a1e823a5b8e26266356a2e1d22e5904b0652dcff6e3c0e72067&type=dir\n")
+
+	//09e881f57befa1eacec744e3857a36f0d9d5dd1fa72ba96564b467a3d7d0c0d5
+	obj_dir := []byte("tree 423\n" +
+		"acl=u::rw-,g::r--,o::r--&name=baz&target=foo&type=symlink\n" +
+		"acl=u::rw-,g::r--,o::r--&name=foo&ref=sha3-256:fa50ca1fc739852528ecc149b424a8ccbdf84b73c8718cde4525f2a410d79244&type=file\n" +
+		"acl=u::rwx,g::r-x,o::r-x&name=bar&ref=sha3-256:4a10682307d5b5dc072d1b862497296640176109347b149aad38cd640000491b&type=file\n" +
+		"acl=u::rwx,g::r-x,o::r-x&name=sub&ref=sha3-256:f1716a1b0cad23b6faab9712243402b8f8e7919c377fc5d5d87bd465cef056d7&type=dir\n")
+
+	wantObject(t, s, "sha3-256:4a10682307d5b5dc072d1b862497296640176109347b149aad38cd640000491b", obj_emptyfile)
+	wantObject(t, s, "sha3-256:ba632076629ff33238850c870fcb51e4b7b67b3d9dcb66314adbcf1770a5fea7", obj_fooblob)
+	wantObject(t, s, "sha3-256:fa50ca1fc739852528ecc149b424a8ccbdf84b73c8718cde4525f2a410d79244", obj_foofile)
+	wantObject(t, s, "sha3-256:1dc6fae780ae4a1e823a5b8e26266356a2e1d22e5904b0652dcff6e3c0e72067", obj_emptytree)
+	wantObject(t, s, "sha3-256:f1716a1b0cad23b6faab9712243402b8f8e7919c377fc5d5d87bd465cef056d7", obj_subdir) //!
+	wantObject(t, s, "sha3-256:09e881f57befa1eacec744e3857a36f0d9d5dd1fa72ba96564b467a3d7d0c0d5", obj_dir)    //!
+}
diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 0000000..32b8325
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,20 @@
+package cache
+
+import (
+	"code.laria.me/petrific/objects"
+	"time"
+)
+
+type Cache interface {
+	PathUpdated(path string) (mtime time.Time, id objects.ObjectId, ok bool)
+	SetPathUpdated(path string, mtime time.Time, id objects.ObjectId)
+}
+
+type NopCache struct{}
+
+func (NopCache) PathUpdated(_ string) (_ time.Time, _ objects.ObjectId, ok bool) {
+	ok = false
+	return
+}
+
+func (NopCache) SetPathUpdated(_ string, _ time.Time, _ objects.ObjectId) {}
diff --git a/fs/fs.go b/fs/fs.go
new file mode 100644
index 0000000..cbfeb44
--- /dev/null
+++ b/fs/fs.go
@@ -0,0 +1,41 @@
+package fs
+
+import (
+	"io"
+	"time"
+)
+
+type FileType string
+
+const (
+	FFile    FileType = "file"
+	FDir     FileType = "dir"
+	FSymlink FileType = "symlink"
+)
+
+type File interface {
+	Type() FileType // Depending on type, the File must also implement RegularFile (FFile), Dir (FDir) or Symlink (FSymlink)
+	Name() string
+	Executable() bool // For now we will only record the executable bit instead of all permission bits
+	ModTime() time.Time
+	Delete() error
+}
+
+type RegularFile interface {
+	File
+	Open() (io.ReadWriteCloser, error)
+}
+
+type Dir interface {
+	File
+	Readdir() ([]File, error)
+
+	CreateChildFile(name string, exec bool) (RegularFile, error)
+	CreateChildDir(name string) (Dir, error)
+	CreateChildSymlink(name string, target string) (Symlink, error)
+}
+
+type Symlink interface {
+	File
+	Readlink() (string, error)
+}
diff --git a/fs/memory.go b/fs/memory.go
new file mode 100644
index 0000000..5f5d327
--- /dev/null
+++ b/fs/memory.go
@@ -0,0 +1,130 @@
+package fs
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"time"
+)
+
+type memfsBase struct {
+	parent *memfsDir
+	name   string
+	exec   bool
+	mtime  time.Time
+}
+
+func (b memfsBase) Name() string       { return b.name }
+func (b memfsBase) Executable() bool   { return b.exec }
+func (b memfsBase) ModTime() time.Time { return b.mtime }
+
+func (b memfsBase) Delete() error {
+	if b.parent == nil {
+		return errors.New("Root entry can not be deleted")
+	}
+	b.parent.deleteChild(b.name)
+	return nil
+}
+
+type memfsFile struct {
+	memfsBase
+	content *bytes.Buffer
+}
+
+func (memfsFile) Type() FileType { return FFile }
+
+func (f memfsFile) Open() (io.ReadWriteCloser, error) {
+	return f, nil
+}
+
+func (f memfsFile) Read(p []byte) (int, error) {
+	return f.content.Read(p)
+}
+
+func (f memfsFile) Write(p []byte) (int, error) {
+	return f.content.Write(p)
+}
+
+func (memfsBase) Close() error {
+	return nil
+}
+
+type memfsDir struct {
+	memfsBase
+	children map[string]File
+}
+
+func (memfsDir) Type() FileType { return FDir }
+
+func (d memfsDir) Readdir() ([]File, error) {
+	l := make([]File, 0, len(d.children))
+
+	for _, f := range d.children {
+		l = append(l, f)
+	}
+
+	return l, nil
+}
+
+func (d memfsDir) createChildBase(name string, exec bool) memfsBase {
+	return memfsBase{
+		parent: &d,
+		name:   name,
+		exec:   exec,
+		mtime:  time.Now(),
+	}
+}
+
+func (d memfsDir) CreateChildFile(name string, exec bool) (RegularFile, error) {
+	child := memfsFile{
+		memfsBase: d.createChildBase(name, exec),
+		content:   new(bytes.Buffer),
+	}
+	d.children[name] = child
+	return child, nil
+}
+
+func (d memfsDir) CreateChildDir(name string) (Dir, error) {
+	child := memfsDir{
+		memfsBase: d.createChildBase(name, true),
+		children:  make(map[string]File),
+	}
+	d.children[name] = child
+	return child, nil
+}
+
+func (d memfsDir) CreateChildSymlink(name string, target string) (Symlink, error) {
+	child := memfsSymlink{
+		memfsBase: d.createChildBase(name, false),
+		target:    target,
+	}
+	d.children[name] = child
+	return child, nil
+}
+
+func (d *memfsDir) deleteChild(name string) {
+	delete(d.children, name)
+}
+
+func NewMemoryFSRoot(name string) Dir {
+	return memfsDir{
+		memfsBase: memfsBase{
+			parent: nil,
+			name:   name,
+			exec:   true,
+			mtime:  time.Now(),
+		},
+		children: make(map[string]File),
+	}
+}
+
+type memfsSymlink struct {
+	memfsBase
+	target string
+}
+
+func (memfsSymlink) Type() FileType { return FSymlink }
+
+func (s memfsSymlink) Readlink() (string, error) {
+	return s.target, nil
+}
diff --git a/fs/os.go b/fs/os.go
new file mode 100644
index 0000000..f251c66
--- /dev/null
+++ b/fs/os.go
@@ -0,0 +1,133 @@
+package fs
+
+import (
+	"io"
+	"os"
+	"time"
+)
+
+func openOSFile(path string) (osFile, error) {
+	fi, err := os.Lstat(path)
+	if err != nil {
+		return osFile{}, err
+	}
+
+	return osFile{
+		fullpath: path,
+		fi:       fi,
+	}, nil
+}
+
+type osFile struct {
+	fullpath string
+	fi       os.FileInfo
+}
+
+func (f osFile) Type() FileType {
+	m := f.fi.Mode()
+	if m.IsDir() {
+		return FDir
+	}
+	if m.IsRegular() {
+		return FFile
+	}
+	if m&os.ModeSymlink != 0 {
+		return FSymlink
+	}
+	return "unknown"
+}
+
+func (f osFile) Name() string {
+	return f.fi.Name()
+}
+
+func (f osFile) Executable() bool {
+	return f.fi.Mode()&0100 != 0 // x bit set for user?
+}
+
+func (f osFile) ModTime() time.Time {
+	return f.fi.ModTime()
+}
+
+func (f osFile) Delete() error {
+	return os.RemoveAll(f.fullpath)
+}
+
+func (f osFile) Open() (io.ReadWriteCloser, error) {
+	fh, err := os.Open(f.fullpath)
+	if err != nil {
+		return nil, err
+	}
+	return fh, nil
+}
+
+func (f osFile) Readdir() (list []File, err error) {
+	fh, err := os.Open(f.fullpath)
+	if err != nil {
+		return
+	}
+	defer fh.Close()
+
+	infos, err := fh.Readdir(-1)
+	if err != nil {
+		return
+	}
+
+	for _, fi := range infos {
+		if fi.Name() == "." || fi.Name() == ".." {
+			continue
+		}
+
+		list = append(list, osFile{
+			fullpath: f.fullpath + string(os.PathSeparator) + fi.Name(),
+			fi:       fi,
+		})
+	}
+
+	return
+}
+
+func perms(executable bool) os.FileMode {
+	if executable {
+		return 0755
+	} else {
+		return 0644
+	}
+}
+
+func (f osFile) CreateChildFile(name string, exec bool) (RegularFile, error) {
+	p := f.fullpath + string(os.PathSeparator) + name
+
+	fh, err := os.OpenFile(p, os.O_RDWR|os.O_CREATE, perms(exec))
+	if err != nil {
+		return nil, err
+	}
+	fh.Close()
+
+	return openOSFile(p)
+}
+
+func (f osFile) CreateChildDir(name string) (Dir, error) {
+	p := f.fullpath + string(os.PathSeparator) + name
+
+	if err := os.Mkdir(p, perms(true)); err != nil {
+		return nil, err
+	}
+
+	return openOSFile(p)
+}
+
+func (f osFile) CreateChildSymlink(name string, target string) (Symlink, error) {
+	p := f.fullpath + string(os.PathSeparator) + name
+
+	err := os.Symlink(target, p)
+	if err != nil {
+		return nil, err
+	}
+
+	return openOSFile(p)
+}
+
+func (f osFile) Readlink() (string, error) {
+	return os.Readlink(f.fullpath)
+}
diff --git a/objects/object.go b/objects/object.go
index 4e096ad..b192912 100644
--- a/objects/object.go
+++ b/objects/object.go
@@ -138,3 +138,7 @@ func (ro RawObject) Object() (o Object, err error) {
 	}
 	return
 }
+
+func ToRawObject(o Object) RawObject {
+	return RawObject{Type: o.Type(), Payload: o.Payload()}
+}
diff --git a/objects/object_tree.go b/objects/object_tree.go
index 2a8f982..609aa7e 100644
--- a/objects/object_tree.go
+++ b/objects/object_tree.go
@@ -41,6 +41,15 @@ type TreeEntryBase struct {
 	user, group string
 }
 
+func baseFromExec(exec bool) (base TreeEntryBase) {
+	if exec {
+		base.acl = acl.ACLFromUnixPerms(0755)
+	} else {
+		base.acl = acl.ACLFromUnixPerms(0644)
+	}
+	return
+}
+
 func (teb TreeEntryBase) ACL() acl.ACL {
 	return teb.acl
 }
@@ -54,11 +63,14 @@ func (teb TreeEntryBase) Group() string {
 }
 
 func (teb TreeEntryBase) toProperties() properties {
-	return properties{
-		"acl":   teb.acl.String(),
-		"user":  teb.user,
-		"group": teb.group,
+	props := properties{"acl": teb.acl.String()}
+	if teb.user != "" {
+		props["user"] = teb.user
+	}
+	if teb.group != "" {
+		props["group"] = teb.group
 	}
+	return props
 }
 
 func (a TreeEntryBase) equalContent(b TreeEntryBase) bool {
@@ -70,6 +82,13 @@ type TreeEntryFile struct {
 	Ref ObjectId
 }
 
+func NewTreeEntryFile(ref ObjectId, exec bool) TreeEntryFile {
+	return TreeEntryFile{
+		TreeEntryBase: baseFromExec(exec),
+		Ref:           ref,
+	}
+}
+
 func (tef TreeEntryFile) Type() TreeEntryType {
 	return TETFile
 }
@@ -90,6 +109,13 @@ type TreeEntryDir struct {
 	Ref ObjectId
 }
 
+func NewTreeEntryDir(ref ObjectId, exec bool) TreeEntryDir {
+	return TreeEntryDir{
+		TreeEntryBase: baseFromExec(exec),
+		Ref:           ref,
+	}
+}
+
 func (ted TreeEntryDir) Type() TreeEntryType {
 	return TETDir
 }
@@ -110,6 +136,13 @@ type TreeEntrySymlink struct {
 	Target string
 }
 
+func NewTreeEntrySymlink(target string, exec bool) TreeEntrySymlink {
+	return TreeEntrySymlink{
+		TreeEntryBase: baseFromExec(exec),
+		Target:        target,
+	}
+}
+
 func (tes TreeEntrySymlink) Type() TreeEntryType {
 	return TETSymlink
 }
diff --git a/objects/object_tree_test.go b/objects/object_tree_test.go
index 3ec9e25..1949375 100644
--- a/objects/object_tree_test.go
+++ b/objects/object_tree_test.go
@@ -49,8 +49,6 @@ var (
 						"": acl.PermR | acl.PermW,
 					},
 				},
-				user:  "user4",
-				group: "group4",
 			},
 			Ref: genId(0x33),
 		},
@@ -59,7 +57,7 @@ var (
 	testTreeSerialization = []byte("" +
 		"acl=u::rw-,g::r--,o::r--&group=group1&name=foo&ref=sha3-256:1111111111111111111111111111111111111111111111111111111111111111&type=file&user=user1\n" +
 		"acl=u::rw-,g::r--,o::r--&group=group3&name=baz&target=%2ff%c3%b6%c3%b6%26b%c3%a4r%2f%f0%9f%92%be&type=symlink&user=user3\n" +
-		"acl=u::rw-,u:user1:rw-,g::r--,o::r--,m::rw-&group=group4&name=%f0%9f%98%83&ref=sha3-256:3333333333333333333333333333333333333333333333333333333333333333&type=file&user=user4\n" +
+		"acl=u::rw-,u:user1:rw-,g::r--,o::r--,m::rw-&name=%f0%9f%98%83&ref=sha3-256:3333333333333333333333333333333333333333333333333333333333333333&type=file\n" +
 		"acl=u::rwx,g::r-x,o::r-x&group=group2&name=bar&ref=sha3-256:2222222222222222222222222222222222222222222222222222222222222222&type=dir&user=user2\n")
 )
 
diff --git a/storage/memory_storage.go b/storage/memory_storage.go
new file mode 100644
index 0000000..0c90981
--- /dev/null
+++ b/storage/memory_storage.go
@@ -0,0 +1,41 @@
+package storage
+
+import (
+	"code.laria.me/petrific/objects"
+)
+
+type MemoryStorage struct {
+	objects map[string][]byte
+	bytype  map[objects.ObjectType][]objects.ObjectId
+}
+
+func NewMemoryStorage() Storage {
+	return MemoryStorage{
+		objects: make(map[string][]byte),
+		bytype:  make(map[objects.ObjectType][]objects.ObjectId),
+	}
+}
+
+func (ms MemoryStorage) Get(id objects.ObjectId) ([]byte, error) {
+	b, ok := ms.objects[id.String()]
+	if !ok {
+		return nil, ObjectNotFound
+	}
+	return b, nil
+}
+
+func (ms MemoryStorage) Has(id objects.ObjectId) (bool, error) {
+	_, ok := ms.objects[id.String()]
+	return ok, nil
+}
+
+func (ms MemoryStorage) Set(id objects.ObjectId, typ objects.ObjectType, raw []byte) error {
+	ms.objects[id.String()] = raw
+	ms.bytype[typ] = append(ms.bytype[typ], id)
+
+	return nil
+}
+
+func (ms MemoryStorage) List(typ objects.ObjectType) ([]objects.ObjectId, error) {
+	return ms.bytype[typ], nil
+}
diff --git a/storage/storage.go b/storage/storage.go
new file mode 100644
index 0000000..424661c
--- /dev/null
+++ b/storage/storage.go
@@ -0,0 +1,37 @@
+package storage
+
+import (
+	"bytes"
+	"code.laria.me/petrific/objects"
+	"errors"
+)
+
+var (
+	ObjectNotFound = errors.New("Object not found")
+)
+
+type Storage interface {
+	Get(id objects.ObjectId) ([]byte, error)
+	Has(id objects.ObjectId) (bool, error)
+	Set(id objects.ObjectId, typ objects.ObjectType, raw []byte) error
+	List(typ objects.ObjectType) ([]objects.ObjectId, error)
+}
+
+func SetObject(s Storage, o objects.RawObject) (id objects.ObjectId, err error) {
+	buf := new(bytes.Buffer)
+
+	id, err = o.SerializeAndId(buf, objects.OIdAlgoDefault)
+	if err != nil {
+		return
+	}
+
+	ok, err := s.Has(id)
+	if err != nil {
+		return
+	}
+
+	if !ok {
+		err = s.Set(id, o.Type, buf.Bytes())
+	}
+	return
+}