1 files changed, 46 insertions, 0 deletions
diff --git a/lib/btrfsutil/open.go b/lib/btrfsutil/open.go
new file mode 100644
index 0000000..c5ee314
--- /dev/null
+++ b/lib/btrfsutil/open.go
@@ -0,0 +1,46 @@
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package btrfsutil
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/datawire/dlib/dlog"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
+	"git.lukeshu.com/btrfs-progs-ng/lib/textui"
+)
+
+func Open(ctx context.Context, flag int, filenames ...string) (*btrfs.FS, error) {
+	fs := new(btrfs.FS)
+	for i, filename := range filenames {
+		dlog.Debugf(ctx, "Adding device file %d/%d %q...", i, len(filenames), filename)
+		osFile, err := os.OpenFile(filename, flag, 0)
+		if err != nil {
+			_ = fs.Close()
+			return nil, fmt.Errorf("device file %q: %w", filename, err)
+		}
+		typedFile := &diskio.OSFile[btrfsvol.PhysicalAddr]{
+			File: osFile,
+		}
+		bufFile := diskio.NewBufferedFile[btrfsvol.PhysicalAddr](
+			typedFile,
+			//nolint:gomnd // False positive: gomnd.ignored-functions=[textui.Tunable] doesn't support type params.
+			textui.Tunable[btrfsvol.PhysicalAddr](16*1024), // block size: 16KiB
+			textui.Tunable(1024),                           // number of blocks to buffer; total of 16MiB
+		)
+		devFile := &btrfs.Device{
+			File: bufFile,
+		}
+		if err := fs.AddDevice(ctx, devFile); err != nil {
+			return nil, fmt.Errorf("device file %q: %w", filename, err)
+		}
+	}
+	return fs, nil
+}