1 files changed, 60 insertions, 0 deletions
diff --git a/lib/containers/set.go b/lib/containers/set.go
new file mode 100644
index 0000000..e20b5be
--- /dev/null
+++ b/lib/containers/set.go
@@ -0,0 +1,60 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package containers
+
+import (
+	"io"
+
+	"git.lukeshu.com/go/lowmemjson"
+	"golang.org/x/exp/constraints"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/maps"
+)
+
+type Set[T constraints.Ordered] map[T]struct{}
+
+var (
+	_ lowmemjson.Encodable = Set[int]{}
+	_ lowmemjson.Decodable = (*Set[int])(nil)
+)
+
+func (o Set[T]) EncodeJSON(w io.Writer) error {
+	return lowmemjson.Encode(w, maps.SortedKeys(o))
+}
+
+func (o *Set[T]) DecodeJSON(r io.RuneScanner) error {
+	c, _, _ := r.ReadRune()
+	if c == 'n' {
+		_, _, _ = r.ReadRune() // u
+		_, _, _ = r.ReadRune() // l
+		_, _, _ = r.ReadRune() // l
+		*o = nil
+		return nil
+	}
+	_ = r.UnreadRune()
+	*o = Set[T]{}
+	return lowmemjson.DecodeArray(r, func(r io.RuneScanner) error {
+		var val T
+		if err := lowmemjson.Decode(r, &val); err != nil {
+			return err
+		}
+		(*o)[val] = struct{}{}
+		return nil
+	})
+}
+
+func (o *Set[T]) Insert(v T) {
+	if o == nil {
+		*o = Set[T]{}
+	}
+	(*o)[v] = struct{}{}
+}
+
+func (o *Set[T]) Delete(v T) {
+	if o == nil {
+		return
+	}
+	delete(*o, v)
+}