object/id: Add algorithm stuff

1 files changed, 60 insertions, 0 deletions

diff --git a/object/id/algorithm_ops.go b/object/id/algorithm_ops.go
new file mode 100644
index 00000000..b746dc5f
--- /dev/null
+++ b/object/id/algorithm_ops.go
@@ -0,0 +1,60 @@
+package id
+
+import "hash"
+
+// EmptyTree returns the object ID of
+// an empty tree ("tree 0\x00")
+// for this algorithm.
+func (algo Algorithm) EmptyTree() ObjectID {
+	return algo.info().emptyTree
+}
+
+// HexLen returns the encoded hexadecimal length.
+func (algo Algorithm) HexLen() int {
+	return algo.Size() * 2
+}
+
+// Size returns the hash size in bytes.
+func (algo Algorithm) Size() int {
+	return algo.info().size
+}
+
+// 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
+}
+
+// PackHashID returns the Git pack/rev hash-id encoding for this algorithm.
+//
+// Unknown algorithms return 0.
+func (algo Algorithm) PackHashID() uint32 {
+	return algo.info().packHashID
+}
+
+// SignatureHeaderName returns the signature header name for this algorithm.
+func (algo Algorithm) SignatureHeaderName() string {
+	return algo.info().signatureHeaderName
+}
+
+// String returns the canonical algorithm name.
+func (algo Algorithm) String() string {
+	return algo.info().name
+}
+
+// Sum computes an object ID from raw data using the selected algorithm.
+func (algo Algorithm) Sum(data []byte) ObjectID {
+	return algo.info().sum(data)
+}
+
+// Zero returns the all-zero object ID for this algorithm.
+func (algo Algorithm) Zero() ObjectID {
+	return ObjectID{
+		algo: algo,
+		data: [maxObjectIDSize]byte{},
+	}
+}