1 files changed, 40 insertions, 0 deletions
diff --git a/hash.go b/hash.go
new file mode 100644
index 00000000..f03866f1
--- /dev/null
+++ b/hash.go
@@ -0,0 +1,40 @@
+package furgit
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"fmt"
+)
+
+// To change the hash algorithm you probably only need to change these two lines...
+
+const HashSize = sha1.Size
+
+var newHash = sha1.Sum
+
+// Hash represents a Git object identifier.
+type Hash [HashSize]byte
+
+// ParseHash converts a hex string into an Hash.
+func ParseHash(s string) (Hash, error) {
+	var id Hash
+	if len(s) != HashSize*2 {
+		return id, fmt.Errorf("furgit: invalid hash length %d", len(s))
+	}
+	data, err := hex.DecodeString(s)
+	if err != nil {
+		return id, fmt.Errorf("furgit: decode hash: %w", err)
+	}
+	copy(id[:], data)
+	return id, nil
+}
+
+// String renders the ID as hex.
+func (id Hash) String() string {
+	return hex.EncodeToString(id[:])
+}
+
+// Bytes returns a mutable copy of the underlying bytes.
+func (id Hash) Bytes() []byte {
+	return append([]byte(nil), id[:]...)
+}