diff options
Diffstat (limited to 'objects/object_file.go')
| -rw-r--r-- | objects/object_file.go | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/objects/object_file.go b/objects/object_file.go index 7551193..6143ec2 100644 --- a/objects/object_file.go +++ b/objects/object_file.go @@ -7,16 +7,20 @@ import ( "strconv" ) +// FileFragment describes a fragment of a file. It consists of the ID of a blob and the size of the blob. +// The size is not necessary for reconstruction (the blob object already has a size) +// but it can speed up random access to the whole file by skipping previous fragments. +// It is serialized as `Properties` (see there) with the keys `blob` (ID of blob object) and `size` (decimal size of the blob) type FileFragment struct { Blob ObjectId Size uint64 } -func (ff FileFragment) toProperties() properties { - return properties{"blob": ff.Blob.String(), "size": strconv.FormatUint(ff.Size, 10)} +func (ff FileFragment) toProperties() Properties { + return Properties{"blob": ff.Blob.String(), "size": strconv.FormatUint(ff.Size, 10)} } -func (ff *FileFragment) fromProperties(p properties) error { +func (ff *FileFragment) fromProperties(p Properties) error { blob, ok := p["blob"] if !ok { return errors.New("Field `blob` is missing") @@ -41,6 +45,19 @@ func (a FileFragment) Equals(b FileFragment) bool { return a.Blob.Equals(b.Blob) && a.Size == b.Size } +// File describes a file object which ties together multiple Blob objects to a file. +// It is an ordered list of `FileFragment`s. The referenced blobs concatencated in the given order are the content of the file. +// +// Example: +// +// blob=sha3-256:1111111111111111111111111111111111111111111111111111111111111111&size=123 +// blob=sha3-256:1111111111111111111111111111111111111111111111111111111111111111&size=123 +// blob=sha3-256:2222222222222222222222222222222222222222222222222222222222222222&size=10 +// +// The file described by this object is 123+123+10 = 256 bytes long and consists of the blobs 111... (two times) and 222... +// +// Since the blob IDs and sizes don't change unless the file itself changes and the format will always serialize the same, +// serializing the same file twice results in exactly the same object with exactly the same ID. It will therefor only be stored once. type File []FileFragment func (f File) Type() ObjectType { @@ -72,7 +89,7 @@ func (f *File) FromPayload(payload []byte) error { continue } - props := make(properties) + props := make(Properties) if err := props.UnmarshalText(line); err != nil { return nil } |