[PATCH v2 3/4] Split "auto" compression mode into its own path

[David Gibson <david@gibson.dropbear.id.au>]

mbuto supports "auto" compression mode where we detect the fastest to
decompress and use it.  This is structured a bit oddly - cpio_compress()
first handles the case of an explicitly selected compressor, then handles
the auto-detected case, redundantly implementing the compression once it
has picked one.

Make this a bit clearer: first handle the "auto" case by calling out to
the testing code, and using that to set the parameter for the specific
compression path.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 mbuto | 53 ++++++++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/mbuto b/mbuto
index 49d032c..eb559fb 100755
--- a/mbuto
+++ b/mbuto
@@ -566,31 +566,11 @@ cpio_init() {
 	fi
 }
 
-# cpio_compress() - Compress archive, test available methods if none is selected
+# compress_select() - Try compressors and pick the fastest to decompress image
 # $1:	Existing CPIO archive
-cpio_compress() {
-	{ [ -z "${COMPRESS}" ] || [ "${COMPRESS}" = "none" ]; } && return
-
-	info "Compressing CPIO archive ${1}"
-
-	if [ "${COMPRESS}" != "auto" ]; then
-		[ "${COMPRESS}" = "lzo" ] && __cmd="lzop" || __cmd="${COMPRESS}"
-
-		cmd_check "${__cmd}"
-		if [ "${__cmd}" = "lz4" ]; then
-			"${__cmd}" -l -f -q -9 "${1}" "${1}.lz4"
-		else
-			"${__cmd}" -f -q -9 -S .lz4 "${1}"
-		fi
-
-		mv "${1}.lz4" "${1}"
-
-		return
-	fi
-
+compress_select() {
 	if [ ! -f "/boot/config-${KERNEL}" ]; then
-		"${GZIP}" -9 "${1}"
-		"${MV}" "${1}.gz" "${1}"
+		echo "gzip"
 		return
 	fi
 
@@ -639,14 +619,29 @@ cpio_compress() {
 		       "${__a}:" "${__size} bytes" "${__time}s"
 	done
 
-	[ "${__pick}" = "lzo" ] && __cmd="lzop" || __cmd="${__pick}"
-	[ "${__cmd}" = "lz4" ] && __opt="-l" || __opt=""
-
-	"${__cmd}" ${__opt} -q -9 -c "${1}" > "${compress_test1}"
 	notice "Picked ${__pick} compression for CPIO"
+	rm ${compress_test1} ${compress_test2}
+	echo "${__pick}"
+}
+
+# cpio_compress() - Compress archive, test available methods if none is selected
+# $1:	Existing CPIO archive
+cpio_compress() {
+	{ [ -z "${COMPRESS}" ] || [ "${COMPRESS}" = "none" ]; } && return
+	[ "${COMPRESS}" = "auto" ] && COMPRESS=$(compress_select "$1")
+
+	info "Compressing CPIO archive ${1}"
+
+	[ "${COMPRESS}" = "lzo" ] && __cmd="lzop" || __cmd="${COMPRESS}"
+
+	cmd_check "${__cmd}"
+	if [ "${__cmd}" = "lz4" ]; then
+		"${__cmd}" -l -f -q -9 "${1}" "${1}.lz4"
+	else
+		"${__cmd}" -f -q -9 -S .lz4 "${1}"
+	fi
 
-	mv "${compress_test1}" "${OUT}"
-	rm "${compress_test2}"
+	mv "${1}.lz4" "${1}"
 }
 
 ################################################################################
-- 
@@ -566,31 +566,11 @@ cpio_init() {
 	fi
 }
 
-# cpio_compress() - Compress archive, test available methods if none is selected
+# compress_select() - Try compressors and pick the fastest to decompress image
 # $1:	Existing CPIO archive
-cpio_compress() {
-	{ [ -z "${COMPRESS}" ] || [ "${COMPRESS}" = "none" ]; } && return
-
-	info "Compressing CPIO archive ${1}"
-
-	if [ "${COMPRESS}" != "auto" ]; then
-		[ "${COMPRESS}" = "lzo" ] && __cmd="lzop" || __cmd="${COMPRESS}"
-
-		cmd_check "${__cmd}"
-		if [ "${__cmd}" = "lz4" ]; then
-			"${__cmd}" -l -f -q -9 "${1}" "${1}.lz4"
-		else
-			"${__cmd}" -f -q -9 -S .lz4 "${1}"
-		fi
-
-		mv "${1}.lz4" "${1}"
-
-		return
-	fi
-
+compress_select() {
 	if [ ! -f "/boot/config-${KERNEL}" ]; then
-		"${GZIP}" -9 "${1}"
-		"${MV}" "${1}.gz" "${1}"
+		echo "gzip"
 		return
 	fi
 
@@ -639,14 +619,29 @@ cpio_compress() {
 		       "${__a}:" "${__size} bytes" "${__time}s"
 	done
 
-	[ "${__pick}" = "lzo" ] && __cmd="lzop" || __cmd="${__pick}"
-	[ "${__cmd}" = "lz4" ] && __opt="-l" || __opt=""
-
-	"${__cmd}" ${__opt} -q -9 -c "${1}" > "${compress_test1}"
 	notice "Picked ${__pick} compression for CPIO"
+	rm ${compress_test1} ${compress_test2}
+	echo "${__pick}"
+}
+
+# cpio_compress() - Compress archive, test available methods if none is selected
+# $1:	Existing CPIO archive
+cpio_compress() {
+	{ [ -z "${COMPRESS}" ] || [ "${COMPRESS}" = "none" ]; } && return
+	[ "${COMPRESS}" = "auto" ] && COMPRESS=$(compress_select "$1")
+
+	info "Compressing CPIO archive ${1}"
+
+	[ "${COMPRESS}" = "lzo" ] && __cmd="lzop" || __cmd="${COMPRESS}"
+
+	cmd_check "${__cmd}"
+	if [ "${__cmd}" = "lz4" ]; then
+		"${__cmd}" -l -f -q -9 "${1}" "${1}.lz4"
+	else
+		"${__cmd}" -f -q -9 -S .lz4 "${1}"
+	fi
 
-	mv "${compress_test1}" "${OUT}"
-	rm "${compress_test2}"
+	mv "${1}.lz4" "${1}"
 }
 
 ################################################################################
-- 
2.44.0