[#222] Add GetRange method in shard

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/local_object_storage/shard/range.go

@@ -0,0 +1,100 @@
+package shard
+
+import (
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobovnicza"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
+)
+
+// RngPrm groups the parameters of GetRange operation.
+type RngPrm struct {
+	ln uint64
+
+	off uint64
+
+	addr *objectSDK.Address
+}
+
+// RngPrm groups resulting values of GetRange operation.
+type RngRes struct {
+	obj *object.Object
+}
+
+// WithAddress is a Rng option to set the address of the requested object.
+//
+// Option is required.
+func (p *RngPrm) WithAddress(addr *objectSDK.Address) *RngPrm {
+	if p != nil {
+		p.addr = addr
+	}
+
+	return p
+}
+
+// WithRange is a GetRange option to set range of requested payload data.
+func (p *RngPrm) WithRange(off uint64, ln uint64) *RngPrm {
+	if p != nil {
+		p.off, p.ln = off, ln
+	}
+
+	return p
+}
+
+// Object returns the requested object part.
+//
+// Instance payload contains the requested range of the original object.
+func (r *RngRes) Object() *object.Object {
+	return r.obj
+}
+
+// GetRange reads part of an object from shard.
+//
+// Returns any error encountered that
+// did not allow to completely read the object part.
+func (s *Shard) GetRange(prm *RngPrm) (*RngRes, error) {
+	var big, small storFetcher
+
+	rng := objectSDK.NewRange()
+	rng.SetOffset(prm.off)
+	rng.SetLength(prm.ln)
+
+	big = func(stor *blobstor.BlobStor, _ *blobovnicza.ID) (*object.Object, error) {
+		getRngBigPrm := new(blobstor.GetRangeBigPrm)
+		getRngBigPrm.SetAddress(prm.addr)
+		getRngBigPrm.SetRange(rng)
+
+		res, err := stor.GetRangeBig(getRngBigPrm)
+		if err != nil {
+			return nil, err
+		}
+
+		obj := object.NewRaw()
+		obj.SetPayload(res.RangeData())
+
+		return obj.Object(), nil
+	}
+
+	small = func(stor *blobstor.BlobStor, id *blobovnicza.ID) (*object.Object, error) {
+		getRngSmallPrm := new(blobstor.GetRangeSmallPrm)
+		getRngSmallPrm.SetAddress(prm.addr)
+		getRngSmallPrm.SetRange(rng)
+		getRngSmallPrm.SetBlobovniczaID(id)
+
+		res, err := stor.GetRangeSmall(getRngSmallPrm)
+		if err != nil {
+			return nil, err
+		}
+
+		obj := object.NewRaw()
+		obj.SetPayload(res.RangeData())
+
+		return obj.Object(), nil
+	}
+
+	obj, err := s.fetchObjectData(prm.addr, big, small)
+
+	return &RngRes{
+		obj: obj,
+	}, err
+}