[make-initrd] [PATCH v6 10/22] bootchain-core: expanded addressing capabilities

["Leonid Krivoshein" <klark.devel@gmail.com>]

Adds support for reverse addressing relative to the current step,
as well as calculating the path to the special device node obtained
in the previous step.

Signed-off-by: Leonid Krivoshein <klark.devel@gmail.com>
---
 features/bootchain-core/README.md             |  6 +++
 .../data/bin/bootchain-sh-functions           | 37 ++++++++++++++++---
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/features/bootchain-core/README.md b/features/bootchain-core/README.md
index 8d341e0..ba66259 100644
--- a/features/bootchain-core/README.md
+++ b/features/bootchain-core/README.md
@@ -49,6 +49,12 @@ us to optimize fill in `initramfs` only which we are need.
 
 - Modularity: loading methods are initially separated from the common
   code and daemon.
+- Via resolve_target() supports not only forward, but also reverse addressing,
+  relative to the current step. For example, a record like `step-3/dir1/dev`
+  will process the result of `dir1/dev`, made in the third step from the current
+  one. Together with the overload of the chain of steps, direct addressing is safe
+  only when storing the numbers of the completed steps in files, whereas reverse
+  relative addressing it is safe in any case and can often be more convenient.
 - Allows you to work with shorter and more familiar paths to special files
   devices thanks to the use of `DEVNAME` along with `dev`.
 
diff --git a/features/bootchain-core/data/bin/bootchain-sh-functions b/features/bootchain-core/data/bin/bootchain-sh-functions
index e73fd35..0eebbaf 100644
--- a/features/bootchain-core/data/bin/bootchain-sh-functions
+++ b/features/bootchain-core/data/bin/bootchain-sh-functions
@@ -27,19 +27,46 @@ get_parameter()
 resolve_target()
 {
 	local target="$1"
+	local where="${target%%/*}"
+	local n="${#where}"
 
-	case "${target%%/*}" in
+	target="${target:$n}"
+
+	case "$where" in
 	'')
 		;;
 	pipe[0-9]|pipe[0-9][0-9]|pipe[0-9][0-9][0-9])
-		target="$mntdir/dst/step${target:4}"
+		[ -d "$mntdir/dst/step${where:4}" ] ||
+			return 0
+		target="$(readlink-e "$mntdir/dst/step${where:4}")${target}"
+		;;
+	step-[1-9]|step-[1-9][0-9]|step-[1-9][0-9][0-9])
+		case "$destdir" in
+		"$mntdir"/dst/step[0-9]*)
+			n="${destdir##*/}"
+			n="$(( ${n:4} - ${where:5} ))"
+			;;
+		*)
+			return 0
+			;;
+		esac
+		[ "$n" -ge 0 ] && [ -d "$mntdir/dst/step$n" ] ||
+			return 0
+		target="$(readlink-e "$mntdir/dst/step$n")${target}"
 		;;
 	*)
 		if [ -z "${prevdir-}" ]; then
-			message "no previous stop to use"
-			return
+			message "no previous step results to use with $name"
+			return 0
+		fi
+		if [ -z "$target" ] &&
+		   [ "$where" = DEVNAME ] &&
+		   [ -s "$prevdir"/DEVNAME ]
+		then
+			read -r target <"$prevdir"/DEVNAME ||:
+		else
+			target="$prevdir/${where#/}${target}"
 		fi
-		target="$prevdir/${target#/}"
 		;;
 	esac
 
-- 
2.24.1