[#176] localstore: Implement primary BlobStor

Implement primary local BLOB storage based on filesystem tree.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/blobstor/getrange.go

@@ -0,0 +1,82 @@
+package blobstor
+
+import (
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/pkg/errors"
+)
+
+// GetRangePrm groups the parameters of GetRange operation.
+type GetRangePrm struct {
+	off, ln uint64
+
+	addr *objectSDK.Address
+}
+
+// GetRangeRes groups resulting values of GetRange operation.
+type GetRangeRes struct {
+	rngData []byte
+}
+
+// WithAddress is a GetRange option to set the address of the requested object.
+//
+// Option is required.
+func (p *GetRangePrm) WithAddress(addr *objectSDK.Address) *GetRangePrm {
+	if p != nil {
+		p.addr = addr
+	}
+
+	return p
+}
+
+// WithPayloadRange is a GetRange option to set range of requested payload data.
+//
+// Option is required.
+func (p *GetRangePrm) WithPayloadRange(off, ln uint64) *GetRangePrm {
+	if p != nil {
+		p.off, p.ln = off, ln
+	}
+
+	return p
+}
+
+// RangeData returns data of the requested payload range.
+func (r *GetRangeRes) RangeData() []byte {
+	return r.rngData
+}
+
+// GetRange reads data of object payload range from BLOB storage.
+//
+// Returns any error encountered that
+// did not allow to completely read the object payload range.
+func (b *BlobStor) GetRange(prm *GetRangePrm) (*GetRangeRes, error) {
+	b.mtx.RLock()
+	defer b.mtx.RUnlock()
+
+	// get compressed object data
+	data, err := b.fsTree.get(prm.addr)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not read object from fs tree")
+	}
+
+	data, err = b.decompressor(data)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not decompress object data")
+	}
+
+	// unmarshal the object
+	obj := object.New()
+	if err := obj.Unmarshal(data); err != nil {
+		return nil, errors.Wrap(err, "could not unmarshal the object")
+	}
+
+	payload := obj.Payload()
+	if pLen := uint64(len(payload)); pLen < prm.ln+prm.off {
+		return nil, errors.Errorf("range is out-of-bounds (payload %d, off %d, ln %d)",
+			pLen, prm.off, prm.ln)
+	}
+
+	return &GetRangeRes{
+		rngData: payload[prm.off : prm.off+prm.ln],
+	}, nil
+}