object: Declare header length limit

It was added to the protocol within
nspcc-dev/neofs-api#262. Also provide
`Object.HeaderLen` method.

Signed-off-by: Leonard Lyubich <leonard@morphbits.io>

client/object_put.go

@@ -269,6 +269,7 @@ func (x *DefaultObjectWriter) GetResult() ResObjectPut {
 }
 
 // ObjectPutInit initiates writing an object through a remote server using NeoFS API protocol.
+// Header length is limited to [object.MaxHeaderLen].
 //
 // The call only opens the transmission channel, explicit recording is done using the [ObjectWriter].
 // Exactly one return value is non-nil. Resulting writer must be finally closed.

object/fmt.go

@@ -12,6 +12,10 @@ import (
 	oid "github.com/nspcc-dev/neofs-sdk-go/object/id"
 )
 
+// MaxHeaderLen is a maximum allowed length of binary object header to be
+// created via NeoFS API protocol.
+const MaxHeaderLen = 16 << 10
+
 var (
 	errCheckSumMismatch = errors.New("payload checksum mismatch")
 	errCheckSumNotSet   = errors.New("payload checksum is not set")

object/object.go

@@ -843,3 +843,8 @@ func formatCheck(v2 *object.Object) error {
 
 	return nil
 }
+
+// HeaderLen returns length of the binary header.
+func (o *Object) HeaderLen() int {
+	return (*object.Object)(o).GetHeader().StableSize()
+}

object/slicer/slicer.go

@@ -30,7 +30,8 @@ var (
 type ObjectWriter interface {
 	// ObjectPutInit initializes and returns a stream of writable data associated
 	// with the object according to its header. Provided header includes at least
-	// container, owner and object ID fields.
+	// container, owner and object ID fields. Header length is limited to
+	// [object.MaxHeaderLen].
 	//
 	// Signer is required and must not be nil. The operation is executed on behalf of
 	// the account corresponding to the specified Signer, which is taken into account, in particular, for access control.

pool/object.go

@@ -26,6 +26,7 @@ func (p *Pool) actualSigner(signer user.Signer) user.Signer {
 }
 
 // ObjectPutInit initiates writing an object through a remote server using NeoFS API protocol.
+// Header length is limited to [object.MaxHeaderLen].
 //
 // Operation is executed within a session automatically created by [Pool] unless parameters explicitly override session settings.
 //