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feat: add SpecFromDigest constructor #83

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Merged
alanshaw merged 2 commits into from
Oct 1, 2026
Merged

feat: add SpecFromDigest constructor #83

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9451add
feat: add SpecFromDigest constructor
alanshaw Oct 1, 2026
28089c5
docs: mention SpecFromDigest in BlobSpec docs
Copilot Oct 1, 2026
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16 changes: 11 additions & 5 deletions commands/blob/codec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,16 +25,22 @@ var (
errBothVariants = errors.New("InvalidUnion", "union holds both variants")
)

// SpecFromBlob returns the spec of a blob whose digest is known. Its digest
// code is the digest's own; a digest that is not a multihash has code 0.
func SpecFromBlob(b Blob) BlobSpec {
s := BlobSpec{digest: b.Digest, size: b.Size, valid: true}
if d, err := multihash.Decode(b.Digest); err == nil {
// SpecFromDigest returns the spec of a blob of size bytes whose digest is
// known. Its digest code is the digest's own; a digest that is not a multihash
// has code 0.
func SpecFromDigest(digest multihash.Multihash, size uint64) BlobSpec {

Copilot AI Oct 1, 2026

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Added SpecFromDigest to the BlobSpec constructor documentation in commit 28089c5.

s := BlobSpec{digest: digest, size: size, valid: true}
if d, err := multihash.Decode(digest); err == nil {
s.code = d.Code
}
return s
}

// SpecFromBlob returns the spec of a blob whose digest is known.
func SpecFromBlob(b Blob) BlobSpec {
return SpecFromDigest(b.Digest, b.Size)
}

// SpecFromDigestCode returns the spec of a blob of size bytes whose digest is
// to be computed with the multihash function code.
func SpecFromDigestCode(code, size uint64) BlobSpec {
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3 changes: 2 additions & 1 deletion commands/blob/spec_test.go
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Expand Up @@ -56,7 +56,8 @@ func TestBlobSpecRoundTrip(t *testing.T) {

func TestBlobSpecAccessors(t *testing.T) {
digest := testutil.RandomMultihash(t)
byDigest := blob.SpecFromBlob(blob.Blob{Digest: digest, Size: 7})
byDigest := blob.SpecFromDigest(digest, 7)
require.Equal(t, blob.SpecFromBlob(blob.Blob{Digest: digest, Size: 7}), byDigest, "a Blob specifies the same blob")
got, ok := byDigest.Digest()
require.True(t, ok)
require.Equal(t, digest, got)
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8 changes: 4 additions & 4 deletions commands/blob/types.go
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Expand Up @@ -21,10 +21,10 @@ type Blob struct {
// compute it as the data streams. A spec naming a digest has the digest's
// code too.
//
// Construct one with [SpecFromBlob] or [SpecFromDigestCode]. Encoding the zero
// value fails, as does decoding a spec that names both a digest and a digest
// code, or neither. The codec is hand-written (codec.go), over the generated
// codec of [BlobSpecModel].
// Construct one with [SpecFromBlob], [SpecFromDigest] or [SpecFromDigestCode].
// Encoding the zero value fails, as does decoding a spec that names both a
// digest and a digest code, or neither. The codec is hand-written (codec.go),
// over the generated codec of [BlobSpecModel].
type BlobSpec struct {
digest multihash.Multihash
code uint64
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