[#205] object: Initial EC implementation

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

object/erasurecode/target.go

@@ -0,0 +1,44 @@
+package erasurecode
+
+import (
+	"context"
+	"crypto/ecdsa"
+
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/transformer"
+)
+
+// Target accepts regular objects and splits them into erasure-coded chunks.
+type Target struct {
+	c    *Constructor
+	key  *ecdsa.PrivateKey
+	next transformer.ObjectWriter
+}
+
+// ObjectWriter is an interface of the object writer that writes prepared object.
+type ObjectWriter interface {
+	WriteObject(context.Context, *objectSDK.Object) error
+}
+
+// NewTarget returns new target instance.
+func NewTarget(c *Constructor, key *ecdsa.PrivateKey, next ObjectWriter) *Target {
+	return &Target{
+		c:    c,
+		key:  key,
+		next: next,
+	}
+}
+
+// WriteObject implements the transformer.ObjectWriter interface.
+func (t *Target) WriteObject(ctx context.Context, obj *objectSDK.Object) error {
+	parts, err := t.c.Split(obj, t.key)
+	if err != nil {
+		return err
+	}
+	for i := range parts {
+		if err := t.next.WriteObject(ctx, parts[i]); err != nil {
+			return err
+		}
+	}
+	return nil
+}