link: Create link object payload message

It describes future protocol version's link object payload. Child objects list
will be moved from the header to the payload. This is done due to the header
size restrictions. Closes #263.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Added
 - Numeric operands for object search queries (#265)
+- Link object payload message (#263)
 
 ### Changed
 

link/types.proto

@@ -0,0 +1,20 @@
+syntax = "proto3";
+
+package neo.fs.v2.link;
+
+option go_package = "github.com/nspcc-dev/neofs-api-go/v2/link/grpc;link";
+option csharp_namespace = "Neo.FileStorage.API.Link";
+
+import "refs/types.proto";
+
+// Link is a payload of helper objects that contain the full list of the split
+// chain objects' IDs. It is created only after the whole split chain is known
+// and signed. This object is the only object that refers to every "child object"
+// ID. It is NOT required for the original object assembling. It MUST have ALL
+// the "child objects" IDs. IDs MUST be ordered according to the original payload
+// split, meaning the first payload part holder MUST be placed at the first place
+// in the corresponding link object.
+message Link {
+  // Full list of the "child" object IDs.
+  repeated neo.fs.v2.refs.ObjectID children = 1 [json_name = "children"];
+}

object/types.proto

@@ -185,6 +185,8 @@ message Header {
     // `header` field of the parent object. Used to reconstruct parent.
     Header parent_header = 4 [json_name = "parentHeader"];
 
+    // DEPRECATED. Was used before creating the separate LINK object type. Keep
+    // child objects list in the LINK object's payload.
     // List of identifiers of the objects generated by splitting current one.
     repeated neo.fs.v2.refs.ObjectID children = 5 [json_name = "children"];
 

proto-docs/link.md

@@ -0,0 +1,66 @@
+# Protocol Documentation
+<a name="top"></a>
+
+## Table of Contents
+
+- [link/types.proto](#link/types.proto)
+
+  - Messages
+    - [Link](#neo.fs.v2.link.Link)
+
+
+- [Scalar Value Types](#scalar-value-types)
+
+
+
+<a name="link/types.proto"></a>
+<p align="right"><a href="#top">Top</a></p>
+
+## link/types.proto
+
+
+ <!-- end services -->
+
+
+<a name="neo.fs.v2.link.Link"></a>
+
+### Message Link
+Link is a payload of helper objects that contain the full list of the split
+chain objects' IDs. It is created only after the whole split chain is known
+and signed. This object is the only object that refers to every "child object"
+ID. It is NOT required for the original object assembling. It MUST have ALL
+the "child objects" IDs. IDs MUST be ordered according to the original payload
+split, meaning the first payload part holder MUST be placed at the first place
+in the corresponding link object.
+
+
+| Field | Type | Label | Description |
+| ----- | ---- | ----- | ----------- |
+| children | [neo.fs.v2.refs.ObjectID](#neo.fs.v2.refs.ObjectID) | repeated | Full list of the "child" object IDs. |
+
+ <!-- end messages -->
+
+ <!-- end enums -->
+
+
+
+## Scalar Value Types
+
+| .proto Type | Notes | C++ Type | Java Type | Python Type |
+| ----------- | ----- | -------- | --------- | ----------- |
+| <a name="double" /> double |  | double | double | float |
+| <a name="float" /> float |  | float | float | float |
+| <a name="int32" /> int32 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead. | int32 | int | int |
+| <a name="int64" /> int64 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead. | int64 | long | int/long |
+| <a name="uint32" /> uint32 | Uses variable-length encoding. | uint32 | int | int/long |
+| <a name="uint64" /> uint64 | Uses variable-length encoding. | uint64 | long | int/long |
+| <a name="sint32" /> sint32 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s. | int32 | int | int |
+| <a name="sint64" /> sint64 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s. | int64 | long | int/long |
+| <a name="fixed32" /> fixed32 | Always four bytes. More efficient than uint32 if values are often greater than 2^28. | uint32 | int | int |
+| <a name="fixed64" /> fixed64 | Always eight bytes. More efficient than uint64 if values are often greater than 2^56. | uint64 | long | int/long |
+| <a name="sfixed32" /> sfixed32 | Always four bytes. | int32 | int | int |
+| <a name="sfixed64" /> sfixed64 | Always eight bytes. | int64 | long | int/long |
+| <a name="bool" /> bool |  | bool | boolean | boolean |
+| <a name="string" /> string | A string must always contain UTF-8 encoded or 7-bit ASCII text. | string | String | str/unicode |
+| <a name="bytes" /> bytes | May contain any arbitrary sequence of bytes. | string | ByteString | str |
+

proto-docs/object.md

@@ -954,7 +954,7 @@ must be within the same container.
 | previous | [neo.fs.v2.refs.ObjectID](#neo.fs.v2.refs.ObjectID) |  | Identifier of the left split neighbor |
 | parent_signature | [neo.fs.v2.refs.Signature](#neo.fs.v2.refs.Signature) |  | `signature` field of the parent object. Used to reconstruct parent. |
 | parent_header | [Header](#neo.fs.v2.object.Header) |  | `header` field of the parent object. Used to reconstruct parent. |
-| children | [neo.fs.v2.refs.ObjectID](#neo.fs.v2.refs.ObjectID) | repeated | List of identifiers of the objects generated by splitting current one. |
+| children | [neo.fs.v2.refs.ObjectID](#neo.fs.v2.refs.ObjectID) | repeated | DEPRECATED. Was used before creating the separate LINK object type. Keep child objects list in the LINK object's payload. List of identifiers of the objects generated by splitting current one. |
 | split_id | [bytes](#bytes) |  | 16 byte UUIDv4 used to identify the split object hierarchy parts. Must be unique inside container. All objects participating in the split must have the same `split_id` value. |