btrfsprim: Move Key to a separate file

1 files changed, 81 insertions, 0 deletions

diff --git a/lib/btrfs/btrfsprim/key.go b/lib/btrfs/btrfsprim/key.go
new file mode 100644
index 0000000..55f7c05
--- /dev/null
+++ b/lib/btrfs/btrfsprim/key.go
@@ -0,0 +1,81 @@
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package btrfsprim
+
+import (
+	"fmt"
+	"math"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/containers"
+)
+
+type Key struct {
+	ObjectID      ObjID    `bin:"off=0x0, siz=0x8"` // Each tree has its own set of Object IDs.
+	ItemType      ItemType `bin:"off=0x8, siz=0x1"`
+	Offset        uint64   `bin:"off=0x9, siz=0x8"` // The meaning depends on the item type.
+	binstruct.End `bin:"off=0x11"`
+}
+
+// mimics print-tree.c:btrfs_print_key()
+func (key Key) Format(tree ObjID) string {
+	switch tree {
+	case UUID_TREE_OBJECTID:
+		return fmt.Sprintf("(%v %v %#08x)",
+			key.ObjectID.Format(tree),
+			key.ItemType,
+			key.Offset)
+	case ROOT_TREE_OBJECTID, QUOTA_TREE_OBJECTID:
+		return fmt.Sprintf("(%v %v %v)",
+			key.ObjectID.Format(tree),
+			key.ItemType,
+			ObjID(key.Offset).Format(tree))
+	default:
+		if key.Offset == math.MaxUint64 {
+			return fmt.Sprintf("(%v %v -1)",
+				key.ObjectID.Format(tree),
+				key.ItemType)
+		} else {
+			return fmt.Sprintf("(%v %v %v)",
+				key.ObjectID.Format(tree),
+				key.ItemType,
+				key.Offset)
+		}
+	}
+}
+
+func (key Key) String() string {
+	return key.Format(0)
+}
+
+var MaxKey = Key{
+	ObjectID: math.MaxUint64,
+	ItemType: math.MaxUint8,
+	Offset:   math.MaxUint64,
+}
+
+func (key Key) Mm() Key {
+	switch {
+	case key.Offset > 0:
+		key.Offset--
+	case key.ItemType > 0:
+		key.ItemType--
+	case key.ObjectID > 0:
+		key.ObjectID--
+	}
+	return key
+}
+
+func (a Key) Compare(b Key) int {
+	if d := containers.NativeCompare(a.ObjectID, b.ObjectID); d != 0 {
+		return d
+	}
+	if d := containers.NativeCompare(a.ItemType, b.ItemType); d != 0 {
+		return d
+	}
+	return containers.NativeCompare(a.Offset, b.Offset)
+}
+
+var _ containers.Ordered[Key] = Key{}