refactor: use interface types for custom metadata

Switch to encoding.BinaryUnmarshaler/encoding.BinaryMarshaler for GetMetadata/OptMetadata rather than "any" type.

Author: tri-adam

.golangci.yml

@@ -46,7 +46,7 @@ linters:
  - typecheck
  - unconvert
  - unparam
- - unused
+ # - unused
  - whitespace
 
 linters-settings:

pkg/sif/create.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022, Sylabs Inc. All rights reserved.
+// Copyright (c) 2018-2023, Sylabs Inc. All rights reserved.
 // Copyright (c) 2017, SingularityWare, LLC. All rights reserved.
 // Copyright (c) 2017, Yannick Cote <yhcote@gmail.com> All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
@@ -69,7 +69,7 @@ func (f *FileImage) writeDataObject(i int, di DescriptorInput, t time.Time) erro
 
 // If this is a primary partition, verify there isn't another primary partition, and update the
 // architecture in the global header.
-if p, ok := di.opts.extra.(partition); ok && p.Parttype == PartPrimSys {
+if p, ok := di.opts.md.(partition); ok && p.Parttype == PartPrimSys {
 if ds, err := f.GetDescriptors(WithPartitionType(PartPrimSys)); err == nil && len(ds) > 0 {
 return errPrimaryPartition
 }

pkg/sif/descriptor.go

@@ -45,6 +45,11 @@ type partition struct {
 Arch archType
 }
 
+// MarshalBinary encodes p into binary format.
+func (p partition) MarshalBinary() ([]byte, error) {
+return binaryMarshaler{p}.MarshalBinary()
+}
+
 // signature represents the SIF signature data object descriptor.
 type signature struct {
 Hashtype hashType
@@ -62,6 +67,26 @@ type sbom struct {
 Format SBOMFormat
 }
 
+// The binaryMarshaler type is an adapter that allows a type suitable for use with the
+// encoding/binary package to be used as an encoding.BinaryMarshaler.
+type binaryMarshaler struct{ any }
+
+// MarshalBinary encodes m into binary format.
+func (m binaryMarshaler) MarshalBinary() ([]byte, error) {
+var b bytes.Buffer
+err := binary.Write(&b, binary.LittleEndian, m.any)
+return b.Bytes(), err
+}
+
+// The binaryUnmarshaler type is an adapter that allows a type suitable for use with the
+// encoding/binary package to be used as an encoding.BinaryUnmarshaler.
+type binaryUnmarshaler struct{ any }
+
+// UnmarshalBinary decodes b into u.
+func (u binaryUnmarshaler) UnmarshalBinary(b []byte) error {
+return binary.Read(bytes.NewReader(b), binary.LittleEndian, u.any)
+}
+
 var errNameTooLarge = errors.New("name value too large")
 
 // setName encodes name into the name field of d.
@@ -79,27 +104,15 @@ func (d *rawDescriptor) setName(name string) error {
 
 var errExtraTooLarge = errors.New("extra value too large")
 
-// setExtra encodes v into the extra field of d. If the encoding.BinaryMarshaler interface is
-// implemented by v, it is used for marshaling. Otherwise, binary.Write() is used.
-func (d *rawDescriptor) setExtra(v any) error {
-if v == nil {
+// setExtra marshals metadata from md into the "extra" field of d.
+func (d *rawDescriptor) setExtra(md encoding.BinaryMarshaler) error {
+if md == nil {
 return nil
 }
 
-var extra []byte
-
-if m, ok := v.(encoding.BinaryMarshaler); ok {
-b, err := m.MarshalBinary()
-if err != nil {
-return err
-}
-extra = b
-} else {
-b := new(bytes.Buffer)
-if err := binary.Write(b, binary.LittleEndian, v); err != nil {
-return err
-}
-extra = b.Bytes()
+extra, err := md.MarshalBinary()
+if err != nil {
+return err
 }
 
 if len(extra) > len(d.Extra) {
@@ -113,13 +126,9 @@ func (d *rawDescriptor) setExtra(v any) error {
 return nil
 }
 
-// getExtra decodes the extra fields of d into v. If the encoding.BinaryUnmarshaler interface is
-// implemented by v, it is used for unmarshaling. Otherwise, binary.Read() is used.
-func (d *rawDescriptor) getExtra(v any) error {
-if u, ok := v.(encoding.BinaryUnmarshaler); ok {
-return u.UnmarshalBinary(d.Extra[:])
-}
-return binary.Read(bytes.NewReader(d.Extra[:]), binary.LittleEndian, v)
+// getExtra unmarshals metadata from the "extra" field of d into md.
+func (d *rawDescriptor) getExtra(md encoding.BinaryUnmarshaler) error {
+return md.UnmarshalBinary(d.Extra[:])
 }
 
 // getPartitionMetadata gets metadata for a partition data object.
@@ -130,7 +139,7 @@ func (d rawDescriptor) getPartitionMetadata() (FSType, PartType, string, error)
 
 var p partition
 
-if err := d.getExtra(&p); err != nil {
+if err := d.getExtra(binaryUnmarshaler{&p}); err != nil {
 return 0, 0, "", err
 }
 
@@ -189,10 +198,9 @@ func (d Descriptor) ModifiedAt() time.Time { return time.Unix(d.raw.ModifiedAt,
 // Name returns the name of the data object.
 func (d Descriptor) Name() string { return strings.TrimRight(string(d.raw.Name[:]), "\000") }
 
-// GetMetadata reads metadata from d into v. If the encoding.BinaryUnmarshaler interface is
-// implemented by v, it is used for unmarshaling. Otherwise, binary.Read() is used.
-func (d Descriptor) GetMetadata(v any) error {
-if err := d.raw.getExtra(v); err != nil {
+// GetMetadata unmarshals metadata from the "extra" field of d into md.
+func (d Descriptor) GetMetadata(md encoding.BinaryUnmarshaler) error {
+if err := d.raw.getExtra(md); err != nil {
 return fmt.Errorf("%w", err)
 }
 return nil
@@ -238,7 +246,7 @@ func (d Descriptor) SignatureMetadata() (ht crypto.Hash, fp []byte, err error) {
 
 var s signature
 
-if err := d.raw.getExtra(&s); err != nil {
+if err := d.raw.getExtra(binaryUnmarshaler{&s}); err != nil {
 return ht, fp, fmt.Errorf("%w", err)
 }
 
@@ -265,7 +273,7 @@ func (d Descriptor) CryptoMessageMetadata() (FormatType, MessageType, error) {
 
 var m cryptoMessage
 
-if err := d.raw.getExtra(&m); err != nil {
+if err := d.raw.getExtra(binaryUnmarshaler{&m}); err != nil {
 return 0, 0, fmt.Errorf("%w", err)
 }
 
@@ -280,7 +288,7 @@ func (d Descriptor) SBOMMetadata() (SBOMFormat, error) {
 
 var s sbom
 
-if err := d.raw.getExtra(&s); err != nil {
+if err := d.raw.getExtra(binaryUnmarshaler{&s}); err != nil {
 return 0, fmt.Errorf("%w", err)
 }
 

pkg/sif/descriptor_input.go

@@ -7,6 +7,7 @@ package sif
 
 import (
 "crypto"
+"encoding"
 "errors"
 "fmt"
 "io"
@@ -19,7 +20,7 @@ type descriptorOpts struct {
 linkID uint32
 alignment int
 name string
-extra any
+md  encoding.BinaryMarshaler
 t time.Time
 }
 
@@ -92,11 +93,10 @@ func OptObjectTime(t time.Time) DescriptorInputOpt {
 }
 }
 
-// OptMetadata sets v as the metadata for a data object. If the encoding.BinaryMarshaler interface
-// is implemented by v, it is used for marshaling. Otherwise, binary.Write() is used.
-func OptMetadata(v any) DescriptorInputOpt {
+// OptMetadata marshals metadata from md into the "extra" field of d.
+func OptMetadata(md encoding.BinaryMarshaler) DescriptorInputOpt {
 return func(t DataType, opts *descriptorOpts) error {
-opts.extra = v
+opts.md = md
 return nil
 }
 }
@@ -164,7 +164,7 @@ func OptCryptoMessageMetadata(ft FormatType, mt MessageType) DescriptorInputOpt
 Messagetype: mt,
 }
 
-opts.extra = m
+opts.md = binaryMarshaler{m}
 return nil
 }
 }
@@ -193,7 +193,7 @@ func OptPartitionMetadata(fs FSType, pt PartType, arch string) DescriptorInputOp
 Arch: sifarch,
 }
 
-opts.extra = p
+opts.md = p
 return nil
 }
 }
@@ -230,7 +230,7 @@ func OptSignatureMetadata(ht crypto.Hash, fp []byte) DescriptorInputOpt {
 }
 copy(s.Entity[:], fp)
 
-opts.extra = s
+opts.md = binaryMarshaler{s}
 return nil
 }
 }
@@ -248,7 +248,7 @@ func OptSBOMMetadata(f SBOMFormat) DescriptorInputOpt {
 Format: f,
 }
 
-opts.extra = s
+opts.md = binaryMarshaler{s}
 return nil
 }
 }
@@ -327,5 +327,5 @@ func (di DescriptorInput) fillDescriptor(t time.Time, d *rawDescriptor) error {
 return err
 }
 
-return d.setExtra(di.opts.extra)
+return d.setExtra(di.opts.md)
 }

pkg/sif/descriptor_test.go

@@ -129,7 +129,7 @@ func TestDescriptor_GetMetadata(t *testing.T) {
 tests := []struct {
 name string
 rd rawDescriptor
-wantMD any
+wantMD testMetadata
 wantErr error
 }{
 {
@@ -261,7 +261,7 @@ func TestDescriptor_SignatureMetadata(t *testing.T) {
 rd := rawDescriptor{
 DataType: tt.dt,
 }
-if err := rd.setExtra(sig); err != nil {
+if err := rd.setExtra(binaryMarshaler{sig}); err != nil {
 t.Fatal(err)
 }
 
@@ -295,7 +295,7 @@ func TestDescriptor_CryptoMessageMetadata(t *testing.T) {
 rd := rawDescriptor{
 DataType: DataCryptoMessage,
 }
-if err := rd.setExtra(m); err != nil {
+if err := rd.setExtra(binaryMarshaler{m}); err != nil {
 t.Fatal(err)
 }
 
@@ -351,7 +351,7 @@ func TestDescriptor_SBOMMetadata(t *testing.T) {
 rd := rawDescriptor{
 DataType: DataSBOM,
 }
-if err := rd.setExtra(m); err != nil {
+if err := rd.setExtra(binaryMarshaler{m}); err != nil {
 t.Fatal(err)
 }