[#462] Implement PATCH for regular objects

Signed-off-by: Marina Biryukova <m.biryukova@yadro.com>

api/layer/patch.go

@@ -0,0 +1,78 @@
+package layer
+
+import (
+	"context"
+	"encoding/hex"
+	"fmt"
+	"io"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
+)
+
+type PatchObjectParams struct {
+	Object            *data.ObjectInfo
+	BktInfo           *data.BucketInfo
+	NewBytes          io.Reader
+	Range             *RangeParams
+	VersioningEnabled bool
+}
+
+func (n *Layer) PatchObject(ctx context.Context, p *PatchObjectParams) (*data.ExtendedObjectInfo, error) {
+	if p.Object.Headers[AttributeDecryptedSize] != "" {
+		return nil, fmt.Errorf("patch encrypted object")
+	}
+
+	if p.Object.Headers[MultipartObjectSize] != "" {
+		// TODO: support multipart object patch
+		return nil, fmt.Errorf("patch multipart object")
+	}
+
+	prmPatch := PrmObjectPatch{
+		Container:  p.BktInfo.CID,
+		Object:     p.Object.ID,
+		Payload:    p.NewBytes,
+		Range:      p.Range,
+		ObjectSize: p.Object.Size,
+	}
+	n.prepareAuthParameters(ctx, &prmPatch.PrmAuth, p.BktInfo.Owner)
+
+	objID, err := n.frostFS.PatchObject(ctx, prmPatch)
+	if err != nil {
+		return nil, fmt.Errorf("patch object: %w", err)
+	}
+
+	obj, err := n.objectHead(ctx, p.BktInfo, objID)
+	if err != nil {
+		return nil, fmt.Errorf("head object: %w", err)
+	}
+
+	payloadChecksum, _ := obj.PayloadChecksum()
+	hashSum := hex.EncodeToString(payloadChecksum.Value())
+	newVersion := &data.NodeVersion{
+		BaseNodeVersion: data.BaseNodeVersion{
+			OID:      objID,
+			ETag:     hashSum,
+			FilePath: p.Object.Name,
+			Size:     obj.PayloadSize(),
+			Created:  &p.Object.Created,
+			Owner:    &n.gateOwner,
+			// TODO: Add creation epoch
+		},
+		IsUnversioned: !p.VersioningEnabled,
+		IsCombined:    p.Object.Headers[MultipartObjectSize] != "",
+	}
+
+	if newVersion.ID, err = n.treeService.AddVersion(ctx, p.BktInfo, newVersion); err != nil {
+		return nil, fmt.Errorf("couldn't add new verion to tree service: %w", err)
+	}
+
+	p.Object.ID = objID
+	p.Object.Size = obj.PayloadSize()
+	p.Object.MD5Sum = ""
+	p.Object.HashSum = hashSum
+
+	return &data.ExtendedObjectInfo{
+		ObjectInfo:  p.Object,
+		NodeVersion: newVersion,
+	}, nil
+}