Factor rebuildmappings.MapLogicalSums out of inspect_dbgsums

1 files changed, 92 insertions, 0 deletions

diff --git a/lib/btrfsprogs/btrfsinspect/rebuildmappings/csumitems.go b/lib/btrfsprogs/btrfsinspect/rebuildmappings/csumitems.go
new file mode 100644
index 0000000..90a15b0
--- /dev/null
+++ b/lib/btrfsprogs/btrfsinspect/rebuildmappings/csumitems.go
@@ -0,0 +1,92 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package rebuildmappings
+
+import (
+	"context"
+	"strings"
+
+	"github.com/datawire/dlib/dlog"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfssum"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfsprogs/btrfsinspect"
+	"git.lukeshu.com/btrfs-progs-ng/lib/maps"
+)
+
+func MapLogicalSums(ctx context.Context, scanResults btrfsinspect.ScanDevicesResult) btrfssum.SumRunWithGaps[btrfsvol.LogicalAddr] {
+	dlog.Info(ctx, "Mapping the logical address space...")
+	type record struct {
+		Gen btrfs.Generation
+		Sum btrfssum.ShortSum
+	}
+	addrspace := make(map[btrfsvol.LogicalAddr]record)
+	var sumSize int
+	for _, devResults := range scanResults {
+		sumSize = devResults.Checksums.ChecksumSize
+		for _, sumItem := range devResults.FoundExtentCSums {
+			_ = sumItem.Sums.Walk(ctx, func(pos btrfsvol.LogicalAddr, sum btrfssum.ShortSum) error {
+				new := record{
+					Gen: sumItem.Generation,
+					Sum: sum,
+				}
+				if old, ok := addrspace[pos]; ok {
+					switch {
+					case old.Gen > new.Gen:
+						// do nothing
+					case old.Gen < new.Gen:
+						addrspace[pos] = new
+					case old.Gen == new.Gen:
+						if old != new {
+							dlog.Errorf(ctx, "mismatch of laddr=%v sum: %v != %v", pos, old, new)
+						}
+					}
+				} else {
+					addrspace[pos] = new
+				}
+				return nil
+			})
+		}
+	}
+	dlog.Info(ctx, "... done mapping")
+
+	var flattened btrfssum.SumRunWithGaps[btrfsvol.LogicalAddr]
+	if len(addrspace) == 0 {
+		return flattened
+	}
+
+	dlog.Info(ctx, "Flattening the map ...")
+	var curAddr btrfsvol.LogicalAddr
+	var curSums strings.Builder
+	for _, laddr := range maps.SortedKeys(addrspace) {
+		if laddr != curAddr+(btrfsvol.LogicalAddr(curSums.Len()/sumSize)*btrfssum.BlockSize) {
+			if curSums.Len() > 0 {
+				flattened.Runs = append(flattened.Runs, btrfssum.SumRun[btrfsvol.LogicalAddr]{
+					ChecksumSize: sumSize,
+					Addr:         curAddr,
+					Sums:         btrfssum.ShortSum(curSums.String()),
+				})
+			}
+			curAddr = laddr
+			curSums.Reset()
+		}
+		curSums.WriteString(string(addrspace[laddr].Sum))
+	}
+	if curSums.Len() > 0 {
+		flattened.Runs = append(flattened.Runs, btrfssum.SumRun[btrfsvol.LogicalAddr]{
+			ChecksumSize: sumSize,
+			Addr:         curAddr,
+			Sums:         btrfssum.ShortSum(curSums.String()),
+		})
+	}
+	flattened.Addr = flattened.Runs[0].Addr
+	last := flattened.Runs[len(flattened.Runs)-1]
+	end := last.Addr.Add(last.Size())
+	flattened.Size = end.Sub(flattened.Addr)
+	dlog.Info(ctx, "... done flattening")
+
+	return flattened
+}