objectstore/loose: Add loose backend

1 files changed, 41 insertions, 0 deletions

diff --git a/objectstore/loose/paths.go b/objectstore/loose/paths.go
new file mode 100644
index 00000000..ee761f39
--- /dev/null
+++ b/objectstore/loose/paths.go
@@ -0,0 +1,41 @@
+package loose
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objectstore"
+)
+
+// objectPath returns the loose object path for id.
+func (store *Store) objectPath(id objectid.ObjectID) (string, error) {
+	if id.Algorithm() != store.algo {
+		return "", fmt.Errorf("objectstore/loose: object id algorithm mismatch: got %s want %s", id.Algorithm(), store.algo)
+	}
+	hex := id.String()
+	if len(hex) != store.algo.HexLen() {
+		return "", fmt.Errorf("objectstore/loose: malformed object id %q", hex)
+	}
+	return path.Join("objects", hex[:2], hex[2:]), nil
+}
+
+// openObject opens the loose object file for id.
+// Missing files cause objectstore.ErrObjectNotFound.
+func (store *Store) openObject(id objectid.ObjectID) (*os.File, error) {
+	relPath, err := store.objectPath(id)
+	if err != nil {
+		return nil, err
+	}
+	file, err := store.root.Open(relPath)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil, objectstore.ErrObjectNotFound
+		}
+		return nil, err
+	}
+	return file, nil
+}