From cdda325c80a202dd6af861b912f4b3fa161dab5e Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 6 Oct 2022 02:07:53 -0600
Subject: check the sums of file reads

---
 lib/btrfs/csums.go | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 lib/btrfs/csums.go

(limited to 'lib/btrfs/csums.go')

diff --git a/lib/btrfs/csums.go b/lib/btrfs/csums.go
new file mode 100644
index 0000000..bbd19bd
--- /dev/null
+++ b/lib/btrfs/csums.go
@@ -0,0 +1,64 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package btrfs
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsitem"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfssum"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfstree"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
+)
+
+func ChecksumLogical(fs diskio.File[btrfsvol.LogicalAddr], alg btrfssum.CSumType, laddr btrfsvol.LogicalAddr) (btrfssum.CSum, error) {
+	var dat [btrfssum.BlockSize]byte
+	if _, err := fs.ReadAt(dat[:], laddr); err != nil {
+		return btrfssum.CSum{}, err
+	}
+	return alg.Sum(dat[:])
+}
+
+func ChecksumPhysical(dev *Device, alg btrfssum.CSumType, paddr btrfsvol.PhysicalAddr) (btrfssum.CSum, error) {
+	var dat [btrfssum.BlockSize]byte
+	if _, err := dev.ReadAt(dat[:], paddr); err != nil {
+		return btrfssum.CSum{}, err
+	}
+	return alg.Sum(dat[:])
+}
+
+func ChecksumQualifiedPhysical(fs *FS, alg btrfssum.CSumType, paddr btrfsvol.QualifiedPhysicalAddr) (btrfssum.CSum, error) {
+	dev := fs.LV.PhysicalVolumes()[paddr.Dev]
+	if dev == nil {
+		return btrfssum.CSum{}, fmt.Errorf("no such device_id=%v", paddr.Dev)
+	}
+	return ChecksumPhysical(dev, alg, paddr.Addr)
+}
+
+func LookupCSum(fs btrfstree.TreeOperator, alg btrfssum.CSumType, laddr btrfsvol.LogicalAddr) (btrfssum.SumRun[btrfsvol.LogicalAddr], error) {
+	item, err := fs.TreeSearch(btrfsprim.CSUM_TREE_OBJECTID, func(key btrfsprim.Key, size uint32) int {
+		itemBeg := btrfsvol.LogicalAddr(key.Offset)
+		numSums := int64(size) / int64(alg.Size())
+		itemEnd := itemBeg + btrfsvol.LogicalAddr(numSums*btrfssum.BlockSize)
+		switch {
+		case itemEnd <= laddr:
+			return 1
+		case laddr < itemBeg:
+			return -1
+		default:
+			return 0
+		}
+	})
+	if err != nil {
+		return btrfssum.SumRun[btrfsvol.LogicalAddr]{}, err
+	}
+	body, ok := item.Body.(btrfsitem.ExtentCSum)
+	if !ok {
+		return btrfssum.SumRun[btrfsvol.LogicalAddr]{}, fmt.Errorf("item body is %T not ExtentCSum", item.Body)
+	}
+	return body.SumRun, nil
+}
-- 
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