From 06df8642b3c106186ce950352199edea782a30ab Mon Sep 17 00:00:00 2001
From: Evgeniy Kulikov <kim@nspcc.ru>
Date: Wed, 5 Aug 2020 16:47:09 +0300
Subject: [PATCH] Simplify receiving object from NeoFS

- add function to receive object with payload
- simplify receiving object for layer.Get
- simplify receiving object for layer.objectGet

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>
---
 neofs/layer/layer.go  |  37 +-------------
 neofs/layer/object.go | 110 +++++++++++++++++++++++-------------------
 2 files changed, 62 insertions(+), 85 deletions(-)

diff --git a/neofs/layer/layer.go b/neofs/layer/layer.go
index e02b5bd70..80c9c4683 100644
--- a/neofs/layer/layer.go
+++ b/neofs/layer/layer.go
@@ -124,42 +124,7 @@ func (n *layer) Get(ctx context.Context, address refs.Address) (*object.Object,
 		return nil, err
 	}
 
-	var (
-		off int
-		obj *object.Object
-	)
-
-	for {
-		resp, err := cli.Recv()
-		if err != nil {
-			if err == io.EOF {
-				break
-			}
-
-			return nil, err
-		}
-
-		switch o := resp.R.(type) {
-		case *object.GetResponse_Object:
-			obj = o.Object
-
-			_, hdr := obj.LastHeader(object.HeaderType(object.TombstoneHdr))
-			if hdr != nil {
-				return nil, errors.New("object already removed")
-			}
-
-			obj.Payload = make([]byte, obj.SystemHeader.PayloadLength)
-		case *object.GetResponse_Chunk:
-			if obj == nil {
-				return nil, errors.New("object headers not received")
-			}
-			off += copy(obj.Payload[off:], o.Chunk)
-		default:
-			return nil, errors.Errorf("unknown response %T", o)
-		}
-	}
-
-	return obj, nil
+	return receiveObject(cli)
 }
 
 // GetBucketInfo returns bucket name.
diff --git a/neofs/layer/object.go b/neofs/layer/object.go
index f7d599588..bbc9434a1 100644
--- a/neofs/layer/object.go
+++ b/neofs/layer/object.go
@@ -1,7 +1,6 @@
 package layer
 
 import (
-	"bytes"
 	"context"
 	"io"
 	"time"
@@ -260,6 +259,54 @@ func (n *layer) objectHead(ctx context.Context, addr refs.Address) (*object.Obje
 	return res.Object, nil
 }
 
+func receiveObject(cli object.Service_GetClient) (*object.Object, error) {
+	var (
+		off int
+		buf []byte
+		obj *object.Object
+	)
+
+	for {
+		resp, err := cli.Recv()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+
+			return nil, err
+		}
+
+		switch o := resp.R.(type) {
+		case *object.GetResponse_Object:
+
+			if _, hdr := o.Object.LastHeader(object.HeaderType(object.TombstoneHdr)); hdr != nil {
+				return nil, errors.New("object already removed")
+			}
+
+			obj = o.Object
+			buf = make([]byte, obj.SystemHeader.PayloadLength)
+
+			if len(obj.Payload) > 0 {
+				off += copy(buf, obj.Payload)
+			}
+		case *object.GetResponse_Chunk:
+			if obj == nil {
+				return nil, errors.New("object headers not received")
+			}
+			off += copy(buf[off:], o.Chunk)
+		default:
+			return nil, errors.Errorf("unknown response %T", o)
+		}
+	}
+
+	if obj == nil {
+		return nil, errors.New("object headers not received")
+	}
+	obj.Payload = buf
+
+	return obj, nil
+}
+
 // objectGet and write it into provided io.Reader.
 func (n *layer) objectGet(ctx context.Context, p getParams) (*object.Object, error) {
 	conn, err := n.cli.GetConnection(ctx)
@@ -294,58 +341,23 @@ func (n *layer) objectGet(ctx context.Context, p getParams) (*object.Object, err
 	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
 	defer cancel()
 
-	getClient, err := object.NewServiceClient(conn).Get(ctx, req)
-	if err != nil {
+	var obj *object.Object
+
+	if cli, err := object.NewServiceClient(conn).Get(ctx, req); err != nil {
+		return nil, err
+	} else if obj, err = receiveObject(cli); err != nil {
+		return nil, err
+	} else if ln := int64(obj.SystemHeader.PayloadLength); p.start+p.length > ln {
+		return nil, errors.Errorf("slice bounds out of range: len = %d, start = %d, offset = %d",
+			ln, p.start, p.length)
+	} else if _, err = p.writer.Write(obj.Payload[p.start : p.start+p.length]); err != nil {
 		return nil, err
 	}
 
-	var (
-		headerReceived bool
+	// remove payload:
+	obj.Payload = nil
 
-		buf       = new(bytes.Buffer)
-		objHeader = new(object.Object)
-	)
-
-	for {
-		resp, err := getClient.Recv()
-		if err != nil {
-			if err == io.EOF {
-				break
-			}
-
-			return nil, err
-		}
-
-		if !headerReceived {
-			objHeader = resp.GetObject()
-
-			_, hdr := objHeader.LastHeader(object.HeaderType(object.TombstoneHdr))
-			if hdr != nil {
-				return nil, errors.New("object already removed")
-			}
-
-			_, err = buf.Write(objHeader.Payload)
-			if err != nil && err != io.EOF {
-				return nil, err
-			}
-
-			headerReceived = true
-
-			continue
-		}
-
-		chunk := resp.GetChunk()
-
-		_, err = buf.Write(chunk)
-		if err != nil && err != io.EOF {
-			return nil, err
-		}
-	}
-
-	buf = bytes.NewBuffer(buf.Bytes()[p.start : p.start+p.length])
-	_, err = io.Copy(p.writer, buf)
-
-	return objHeader, err
+	return obj, nil
 }
 
 // objectPut into neofs, took payload from io.Reader.