[#222] Update Range method in storage engine

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

pkg/local_object_storage/engine/range.go

@@ -0,0 +1,123 @@
+package engine
+
+import (
+	"errors"
+
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase/v2"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
+	"go.uber.org/zap"
+)
+
+// RngPrm groups the parameters of GetRange operation.
+type RngPrm struct {
+	off, ln uint64
+
+	addr *objectSDK.Address
+}
+
+// GetRes groups resulting values of GetRange operation.
+type RngRes struct {
+	obj *object.Object
+}
+
+// WithAddress is a GetRng 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
+}
+
+// WithPayloadRange is a GetRange option to set range of requested payload data.
+//
+// Missing an option or calling with zero length is equivalent
+// to getting the full payload range.
+func (p *RngPrm) WithPayloadRange(off, 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 local storage.
+//
+// Returns any error encountered that
+// did not allow to completely read the object part.
+//
+// Returns ErrNotFound if requested object is missing in local storage.
+func (e *StorageEngine) GetRange(prm *RngPrm) (*RngRes, error) {
+	var (
+		obj *object.Object
+
+		alreadyRemoved = false
+	)
+
+	shPrm := new(shard.RngPrm).
+		WithAddress(prm.addr).
+		WithRange(prm.off, prm.ln)
+
+	e.iterateOverSortedShards(prm.addr, func(_ int, sh *shard.Shard) (stop bool) {
+		res, err := sh.GetRange(shPrm)
+		if err != nil {
+			switch {
+			case errors.Is(err, object.ErrNotFound):
+				return false // ignore, go to next shard
+			case errors.Is(err, meta.ErrAlreadyRemoved):
+				alreadyRemoved = true
+
+				return true // stop, return it back
+			default:
+				// TODO: smth wrong with shard, need to be processed, but
+				// still go to next shard
+				e.log.Warn("could not get object from shard",
+					zap.Stringer("shard", sh.ID()),
+					zap.String("error", err.Error()),
+				)
+
+				return false
+			}
+		}
+
+		obj = res.Object()
+
+		return true
+	})
+
+	if obj == nil {
+		if alreadyRemoved {
+			return nil, meta.ErrAlreadyRemoved
+		}
+
+		return nil, object.ErrNotFound
+	}
+
+	return &RngRes{
+		obj: obj,
+	}, nil
+}
+
+// GetRange reads object payload range from local storage by provided address.
+func GetRange(storage *StorageEngine, addr *objectSDK.Address, rng *objectSDK.Range) ([]byte, error) {
+	res, err := storage.GetRange(new(RngPrm).
+		WithAddress(addr).
+		WithPayloadRange(rng.GetOffset(), rng.GetLength()),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return res.Object().Payload(), nil
+}