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-rw-r--r--objectid/objectid.go186
-rw-r--r--objectid/objectid_test.go144
2 files changed, 330 insertions, 0 deletions
diff --git a/objectid/objectid.go b/objectid/objectid.go
new file mode 100644
index 00000000..f97fd197
--- /dev/null
+++ b/objectid/objectid.go
@@ -0,0 +1,186 @@
+// Package objectid provides object ID and algorithm primitives for Git objects.
+package objectid
+
+import (
+ "crypto/sha1"
+ "crypto/sha256"
+ "encoding/hex"
+ "errors"
+ "fmt"
+ "hash"
+)
+
+var (
+ // ErrInvalidAlgorithm indicates an unsupported object ID algorithm.
+ ErrInvalidAlgorithm = errors.New("objectid: invalid algorithm")
+ // ErrInvalidObjectID indicates malformed object ID data.
+ ErrInvalidObjectID = errors.New("objectid: invalid object id")
+)
+
+// maxObjectIDSize MUST be >= the largest supported algorithm size.
+const maxObjectIDSize = sha256.Size
+
+// Algorithm identifies the hash algorithm used for Git object IDs.
+type Algorithm uint8
+
+const (
+ AlgorithmUnknown Algorithm = iota
+ AlgorithmSHA1
+ AlgorithmSHA256
+)
+
+type algorithmDetails struct {
+ name string
+ size int
+ sum func([]byte) ObjectID
+ new func() hash.Hash
+}
+
+var algorithmTable = [...]algorithmDetails{
+ AlgorithmUnknown: {},
+ AlgorithmSHA1: {
+ name: "sha1",
+ size: sha1.Size,
+ sum: func(data []byte) ObjectID {
+ sum := sha1.Sum(data)
+ var id ObjectID
+ copy(id.data[:], sum[:])
+ id.algo = AlgorithmSHA1
+ return id
+ },
+ new: func() hash.Hash {
+ return sha1.New()
+ },
+ },
+ AlgorithmSHA256: {
+ name: "sha256",
+ size: sha256.Size,
+ sum: func(data []byte) ObjectID {
+ sum := sha256.Sum256(data)
+ var id ObjectID
+ copy(id.data[:], sum[:])
+ id.algo = AlgorithmSHA256
+ return id
+ },
+ new: func() hash.Hash {
+ return sha256.New()
+ },
+ },
+}
+
+var algorithmByName = map[string]Algorithm{}
+
+func init() {
+ for algo, info := range algorithmTable {
+ if info.name == "" {
+ continue
+ }
+ algorithmByName[info.name] = Algorithm(algo)
+ }
+}
+
+func (algo Algorithm) info() algorithmDetails {
+ return algorithmTable[algo]
+}
+
+// ParseAlgorithm parses a canonical algorithm name (e.g. "sha1", "sha256").
+func ParseAlgorithm(s string) (Algorithm, bool) {
+ algo, ok := algorithmByName[s]
+ return algo, ok
+}
+
+// Size returns the hash size in bytes.
+func (algo Algorithm) Size() int {
+ return algo.info().size
+}
+
+// String returns the canonical algorithm name.
+func (algo Algorithm) String() string {
+ inf := algo.info()
+ if inf.name == "" {
+ return "unknown"
+ }
+ return inf.name
+}
+
+// HexLen returns the encoded hexadecimal length.
+func (algo Algorithm) HexLen() int {
+ return algo.Size() * 2
+}
+
+// Sum computes an object ID from raw data using the selected algorithm.
+func (algo Algorithm) Sum(data []byte) ObjectID {
+ return algo.info().sum(data)
+}
+
+// New returns a new hash.Hash for this algorithm.
+func (algo Algorithm) New() (hash.Hash, error) {
+ newFn := algo.info().new
+ if newFn == nil {
+ return nil, ErrInvalidAlgorithm
+ }
+ return newFn(), nil
+}
+
+// ObjectID represents a Git object ID.
+type ObjectID struct {
+ algo Algorithm
+ data [maxObjectIDSize]byte
+}
+
+// Algorithm returns the object ID's hash algorithm.
+func (id ObjectID) Algorithm() Algorithm {
+ return id.algo
+}
+
+// Size returns the object ID size in bytes.
+func (id ObjectID) Size() int {
+ return id.algo.Size()
+}
+
+// String returns the canonical hex representation.
+func (id ObjectID) String() string {
+ size := id.Size()
+ return hex.EncodeToString(id.data[:size])
+}
+
+// Bytes returns a copy of the object ID bytes.
+func (id ObjectID) Bytes() []byte {
+ size := id.Size()
+ return append([]byte(nil), id.data[:size]...)
+}
+
+// ParseHex parses an object ID from hex for the specified algorithm.
+func ParseHex(algo Algorithm, s string) (ObjectID, error) {
+ var id ObjectID
+ if algo.Size() == 0 {
+ return id, ErrInvalidAlgorithm
+ }
+ if len(s)%2 != 0 {
+ return id, fmt.Errorf("%w: odd hex length %d", ErrInvalidObjectID, len(s))
+ }
+ if len(s) != algo.HexLen() {
+ return id, fmt.Errorf("%w: got %d chars, expected %d", ErrInvalidObjectID, len(s), algo.HexLen())
+ }
+ decoded, err := hex.DecodeString(s)
+ if err != nil {
+ return id, fmt.Errorf("%w: decode: %v", ErrInvalidObjectID, err)
+ }
+ copy(id.data[:], decoded)
+ id.algo = algo
+ return id, nil
+}
+
+// FromBytes builds an object ID from raw bytes for the specified algorithm.
+func FromBytes(algo Algorithm, b []byte) (ObjectID, error) {
+ var id ObjectID
+ if algo.Size() == 0 {
+ return id, ErrInvalidAlgorithm
+ }
+ if len(b) != algo.Size() {
+ return id, fmt.Errorf("%w: got %d bytes, expected %d", ErrInvalidObjectID, len(b), algo.Size())
+ }
+ copy(id.data[:], b)
+ id.algo = algo
+ return id, nil
+}
diff --git a/objectid/objectid_test.go b/objectid/objectid_test.go
new file mode 100644
index 00000000..2598a4ed
--- /dev/null
+++ b/objectid/objectid_test.go
@@ -0,0 +1,144 @@
+package objectid
+
+import (
+ "bytes"
+ "testing"
+)
+
+func TestParseAlgorithm(t *testing.T) {
+ t.Parallel()
+
+ algo, ok := ParseAlgorithm("sha1")
+ if !ok || algo != AlgorithmSHA1 {
+ t.Fatalf("ParseAlgorithm(sha1) = (%v,%v)", algo, ok)
+ }
+
+ algo, ok = ParseAlgorithm("sha256")
+ if !ok || algo != AlgorithmSHA256 {
+ t.Fatalf("ParseAlgorithm(sha256) = (%v,%v)", algo, ok)
+ }
+
+ if _, ok := ParseAlgorithm("md5"); ok {
+ t.Fatalf("ParseAlgorithm(md5) should fail")
+ }
+}
+
+func TestParseHexRoundtrip(t *testing.T) {
+ t.Parallel()
+
+ tests := []struct {
+ name string
+ algo Algorithm
+ hex string
+ }{
+ {
+ name: "sha1",
+ algo: AlgorithmSHA1,
+ hex: "0123456789abcdef0123456789abcdef01234567",
+ },
+ {
+ name: "sha256",
+ algo: AlgorithmSHA256,
+ hex: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ id, err := ParseHex(tt.algo, tt.hex)
+ if err != nil {
+ t.Fatalf("ParseHex failed: %v", err)
+ }
+ if got := id.String(); got != tt.hex {
+ t.Fatalf("String() = %q, want %q", got, tt.hex)
+ }
+ if got := id.Size(); got != tt.algo.Size() {
+ t.Fatalf("Size() = %d, want %d", got, tt.algo.Size())
+ }
+
+ raw := id.Bytes()
+ if len(raw) != tt.algo.Size() {
+ t.Fatalf("Bytes len = %d, want %d", len(raw), tt.algo.Size())
+ }
+
+ id2, err := FromBytes(tt.algo, raw)
+ if err != nil {
+ t.Fatalf("FromBytes failed: %v", err)
+ }
+ if id2.String() != tt.hex {
+ t.Fatalf("FromBytes roundtrip = %q, want %q", id2.String(), tt.hex)
+ }
+ })
+ }
+}
+
+func TestParseHexErrors(t *testing.T) {
+ t.Parallel()
+
+ tests := []struct {
+ name string
+ algo Algorithm
+ hex string
+ }{
+ {"unknown algo", AlgorithmUnknown, "00"},
+ {"odd len", AlgorithmSHA1, "0"},
+ {"wrong len", AlgorithmSHA1, "0123"},
+ {"invalid hex", AlgorithmSHA1, "zz23456789abcdef0123456789abcdef01234567"},
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ if _, err := ParseHex(tt.algo, tt.hex); err == nil {
+ t.Fatalf("expected ParseHex error")
+ }
+ })
+ }
+}
+
+func TestFromBytesErrors(t *testing.T) {
+ t.Parallel()
+
+ if _, err := FromBytes(AlgorithmUnknown, []byte{1, 2}); err == nil {
+ t.Fatalf("expected FromBytes unknown algo error")
+ }
+ if _, err := FromBytes(AlgorithmSHA1, []byte{1, 2}); err == nil {
+ t.Fatalf("expected FromBytes wrong size error")
+ }
+}
+
+func TestBytesReturnsCopy(t *testing.T) {
+ t.Parallel()
+
+ id, err := ParseHex(AlgorithmSHA1, "0123456789abcdef0123456789abcdef01234567")
+ if err != nil {
+ t.Fatalf("ParseHex failed: %v", err)
+ }
+
+ b1 := id.Bytes()
+ b2 := id.Bytes()
+ if !bytes.Equal(b1, b2) {
+ t.Fatalf("Bytes mismatch")
+ }
+ b1[0] ^= 0xff
+ if bytes.Equal(b1, b2) {
+ t.Fatalf("Bytes should return independent copies")
+ }
+}
+
+func TestAlgorithmSum(t *testing.T) {
+ t.Parallel()
+
+ id1 := AlgorithmSHA1.Sum([]byte("hello"))
+ if id1.Algorithm() != AlgorithmSHA1 || id1.Size() != AlgorithmSHA1.Size() {
+ t.Fatalf("sha1 sum produced invalid object id")
+ }
+
+ id2 := AlgorithmSHA256.Sum([]byte("hello"))
+ if id2.Algorithm() != AlgorithmSHA256 || id2.Size() != AlgorithmSHA256.Size() {
+ t.Fatalf("sha256 sum produced invalid object id")
+ }
+
+ if id1.String() == id2.String() {
+ t.Fatalf("sha1 and sha256 should differ")
+ }
+}
generated by cgit v1.3.1-10-gc9f91 (git 2.54.0) at 2026-05-25 14:58:03 +0000