1 files changed, 44 insertions, 0 deletions
diff --git a/storage/storage.go b/storage/storage.go
index 424661c..45b1973 100644
--- a/storage/storage.go
+++ b/storage/storage.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"code.laria.me/petrific/objects"
 	"errors"
+	"fmt"
+	"io"
 )
 
 var (
@@ -35,3 +37,45 @@ func SetObject(s Storage, o objects.RawObject) (id objects.ObjectId, err error)
 	}
 	return
 }
+
+type IdMismatchErr struct {
+	Want, Have objects.ObjectId
+}
+
+func (iderr IdMismatchErr) Error() string {
+	return fmt.Sprintf("ID verification failed: want %s, have %s", iderr.Want, iderr.Have)
+}
+
+// GetObjects gets an object from a Storage and parses and verifies it (check it's checksum/id)
+func GetObject(s Storage, id objects.ObjectId) (objects.RawObject, error) {
+	raw, err := s.Get(id)
+	if err != nil {
+		return objects.RawObject{}, err
+	}
+
+	idgen := id.Algo.Generator()
+	r := io.TeeReader(bytes.NewReader(raw), idgen)
+
+	obj, err := objects.Unserialize(r)
+	if err != nil {
+		return objects.RawObject{}, err
+	}
+
+	if have_id := idgen.GetId(); !have_id.Equals(id) {
+		return objects.RawObject{}, IdMismatchErr{id, have_id}
+	}
+	return obj, nil
+}
+
+func GetObjectOfType(s Storage, id objects.ObjectId, t objects.ObjectType) (objects.Object, error) {
+	rawobj, err := GetObject(s, id)
+	if err != nil {
+		return nil, err
+	}
+
+	if rawobj.Type != t {
+		return nil, fmt.Errorf("GetObjectOfType: Wrong object type %s (want %s)", rawobj.Type, t)
+	}
+
+	return rawobj.Object()
+}