added fs encryption overlay

pkg/chunk/chunk.go

@@ -0,0 +1,59 @@
+// Copyright (C) 2022 Marius Schellenberger
+
+package chunk
+
+import (
+	"golang.org/x/exp/slices"
+)
+
+type Chunk [2]int64
+
+type Chunks []Chunk
+
+func (Chunks) Less(i, j Chunk) bool { return i[0] < j[0] }
+
+func (cs Chunks) Exists(off int64, n int, size int64) bool {
+	end := off + int64(n)
+	if end > size {
+		end = size
+	}
+	for _, c := range cs {
+		if c[0] <= off && c[1] > off && c[1] >= end {
+			return true
+		}
+	}
+	return false
+}
+
+func (cs *Chunks) Add(off int64, n int) {
+	*cs = append(*cs, Chunk{off, off + int64(n)})
+	cs.merge()
+}
+
+func (cs Chunks) Size() (sum int64) {
+	for _, c := range cs {
+		sum += (c[1] - c[0])
+	}
+	return
+}
+
+func (cs *Chunks) merge() {
+	c := *cs
+	if len(c) < 2 {
+		return
+	}
+	slices.SortFunc(c, c.Less)
+	for i := 0; i < len(c); i++ {
+		if i+1 == len(c) {
+			break
+		}
+		if c[i][1] >= c[i+1][0] {
+			if c[i+1][1] > c[i][1] {
+				c[i][1] = c[i+1][1]
+			}
+			c = slices.Delete(c, i+1, i+2)
+			i--
+		}
+	}
+	*cs = c
+}