1 files changed, 58 insertions, 0 deletions
diff --git a/lib/btrfs/btrfssum/sumrun.go b/lib/btrfs/btrfssum/sumrun.go
new file mode 100644
index 0000000..1000e7a
--- /dev/null
+++ b/lib/btrfs/btrfssum/sumrun.go
@@ -0,0 +1,58 @@
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package btrfssum
+
+import (
+	"context"
+	"io"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+)
+
+type SumRun[Addr btrfsvol.IntAddr[Addr]] struct {
+	// How big a ShortSum is in this Run.
+	ChecksumSize int `json:",omitempty"`
+	// Base address where this run starts.
+	Addr Addr `json:",omitempty"`
+	// All of the ShortSums in this run, concatenated together.
+	Sums ShortSum
+}
+
+func (run SumRun[Addr]) NumSums() int {
+	return len(run.Sums) / run.ChecksumSize
+}
+
+func (run SumRun[Addr]) Size() btrfsvol.AddrDelta {
+	return btrfsvol.AddrDelta(run.NumSums()) * BlockSize
+}
+
+// Get implements diskio.Sequence[int, ShortSum]
+func (run SumRun[Addr]) Get(sumIdx int64) (ShortSum, error) {
+	if sumIdx < 0 || int(sumIdx) >= run.NumSums() {
+		return "", io.EOF
+	}
+	off := int(sumIdx) * run.ChecksumSize
+	return run.Sums[off : off+run.ChecksumSize], nil
+}
+
+func (run SumRun[Addr]) SumForAddr(addr Addr) (ShortSum, bool) {
+	if addr < run.Addr || addr >= run.Addr.Add(run.Size()) {
+		return "", false
+	}
+	off := int((addr-run.Addr)/BlockSize) * run.ChecksumSize
+	return run.Sums[off : off+run.ChecksumSize], true
+}
+
+func (run SumRun[Addr]) Walk(ctx context.Context, fn func(Addr, ShortSum) error) error {
+	for addr, off := run.Addr, 0; off < len(run.Sums); addr, off = addr+BlockSize, off+run.ChecksumSize {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		if err := fn(addr, run.Sums[off:off+run.ChecksumSize]); err != nil {
+			return err
+		}
+	}
+	return nil
+}