From 6a4d33088b57eb58eb5d33f055fac4a8985252cb Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Mon, 25 Jul 2022 16:43:13 +0200
Subject: [dev] Add dev_swap_version: Returns version number of a swap
 partition

---
 modules/dev.inc | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/modules/dev.inc b/modules/dev.inc
index ce58075..7c6e1e7 100644
--- a/modules/dev.inc
+++ b/modules/dev.inc
@@ -183,6 +183,27 @@ dev_get_type() {
 	return 1
 }
 
+# Get version of given swap partition. $1 will be checked for the
+# swap signature, and if found, the version number will be returned.
+# old-style swap will be reported as version 1,
+# new-style as 1 + <version_field>.
+dev_swap_version() {
+	local sig version
+	sig="$( dd if="$1" bs=1 count=10 skip=4086 2> /dev/null )"
+	if [ "$sig" = "SWAP-SPACE" ]; then
+		echo 1
+		return 0
+	elif [ "$sig" = "SWAPSPACE2" ]; then
+		version="$( __read_le "$1" 1024 4 )"
+		# I think there is only '1' currently, but try to be clever...
+		if [ "$version" -gt 0 ] && [ "$version" -lt 8 ]; then
+			echo $(( 1 + version ))
+			return 0
+		fi
+	fi
+	return 1
+}
+
 # stdin = binary data, stdout = raw, unformatted hex
 # __hex2bin()
 
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