[PATCH] cdrom.eclass: Allow image file to be given in CD_ROOT rather than a dir

This adds a app-arch/libarchive dependency, which is assumed to be
present on most systems because of binutils[+debuginfod] ->
elfutils[+libarchive].

The image file will be extracted (not mounted) on demand. The file does
not have be an ISO image, but anything that libarchive can handle.

Mounting would be less intensive, but it is not possible due to
permission and namespace restrictions.

Signed-off-by: James Le Cuirot <[email protected]>
---
 eclass/cdrom.eclass | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/eclass/cdrom.eclass b/eclass/cdrom.eclass
index 73faa996b0c61..c4c8295a05868 100644
--- a/eclass/cdrom.eclass
+++ b/eclass/cdrom.eclass
@@ -1,4 +1,4 @@
-# Copyright 1999-2025 Gentoo Authors
+# Copyright 1999-2026 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: cdrom.eclass
@@ -25,6 +25,10 @@ esac
 
 inherit portability
 
+# For extracting image files referenced in CD_ROOT. This is optional, but users
+# are likely to have it anyway.
+BDEPEND="app-arch/libarchive"
+
 # @ECLASS_VARIABLE: CDROM_OPTIONAL
 # @DEFAULT_UNSET
 # @PRE_INHERIT
@@ -35,6 +39,7 @@ inherit portability
 # conditionally based on USE="cdinstall".
 if [[ ${CDROM_OPTIONAL} == "yes" ]] ; then
 	IUSE="cdinstall"
+	BDEPEND="cdinstall? ( ${BDEPEND} )"
 	PROPERTIES+=" cdinstall? ( interactive )"
 else
 	PROPERTIES+=" interactive"
@@ -99,8 +104,13 @@ cdrom_get_cds() {
 		einfo "the variable CD_ROOT so that it points to the"
 		einfo "directory containing the files."
 		echo
+		einfo "Alternatively, CD_ROOT can point to an image file of"
+		einfo "the CD in ISO format or any supported by libarchive."
+		einfo "Ensure that the file is readable by the Portage user."
+		echo
 		einfo "For example:"
 		einfo "export CD_ROOT=/mnt/cdrom"
+		einfo "export CD_ROOT=/home/user/${PN}.iso"
 		echo
 
 	# Multi disc info.
@@ -118,6 +128,10 @@ cdrom_get_cds() {
 		einfo "the following variables so they point to the right place:"
 		einfo $(printf "CD_ROOT_%d " $(seq ${#}))
 		echo
+		einfo "Alternatively, these variables can point to image files"
+		einfo "of the CDs in ISO format or any supported by libarchive."
+		einfo "Ensure that the files are readable by the Portage user."
+		echo
 		einfo "Or, if you have all the files in the same place, or"
 		einfo "you only have one CD, you can export CD_ROOT"
 		einfo "and that place will be used as the same data source"
@@ -125,6 +139,7 @@ cdrom_get_cds() {
 		echo
 		einfo "For example:"
 		einfo "export CD_ROOT=/mnt/cdrom"
+		einfo "export CD_ROOT_1=/home/user/${PN}-1.iso"
 		echo
 	fi
 
@@ -151,6 +166,10 @@ cdrom_get_cds() {
 # found then the function dies with an error as a rescan will not help
 # in this instance.
 #
+# CD_ROOT and CD_ROOT_# can point at an image file instead of a directory.  The
+# file will be extracted (not mounted) on demand.  The file does not have be an
+# ISO image, but anything that libarchive can handle.
+#
 # Users wanting to set CD_ROOT or CD_ROOT_# for specific packages
 # persistently can do so using Portage's /etc/portage/env feature.
 #
@@ -206,7 +225,7 @@ cdrom_load_next_cd() {
 		IFS=: read -r -a cdset -d "" <<< "${!var}"
 
 		for i in $(seq ${CDROM_SET:-0} ${CDROM_SET:-$((${#cdset[@]} - 1))}); do
-			local f=${cdset[${i}]} point= node= fs= opts=
+			local f=${cdset[${i}]} point= node= fs= opts= orig_cdrom_root=
 
 			if [[ -z ${CDROM_ROOT} ]] ; then
 				while read point node fs opts ; do
@@ -217,6 +236,14 @@ cdrom_load_next_cd() {
 					export CDROM_ROOT=${point}
 				done <<< "$(get_mounts)"
 			else
+				if [[ -f ${CDROM_ROOT} ]]; then
+					rm -rf "${T}/cdrom-root" || die
+					mkdir "${T}/cdrom-root" || die
+					bsdtar -C "${T}/cdrom-root" -xf "${CDROM_ROOT}" || die
+					orig_cdrom_root=${CDROM_ROOT}
+					CDROM_ROOT=${T}/cdrom-root
+				fi
+
 				export CDROM_MATCH=$(_cdrom_glob_match "${CDROM_ROOT}" "${f}")
 			fi
 
@@ -231,7 +258,7 @@ cdrom_load_next_cd() {
 		# CDROM_ROOT is non-empty then this implies that a CD_ROOT
 		# variable was given and we should therefore abort immediately.
 		if [[ -n ${CDROM_ROOT} ]] ; then
-			die "unable to locate CD #${CDROM_CURRENT_CD} root at ${CDROM_ROOT}"
+			die "unable to locate CD #${CDROM_CURRENT_CD} root at ${orig_cdrom_root:-${CDROM_ROOT}}"
 		fi
 
 		if [[ ${showedmsg} -eq 0 ]] ; then
@@ -263,7 +290,7 @@ cdrom_load_next_cd() {
 		read || die "something is screwed with your system"
 	done
 
-	einfo "Found CD #${CDROM_CURRENT_CD} root at ${CDROM_ROOT}"
+	einfo "Found CD #${CDROM_CURRENT_CD} root at ${orig_cdrom_root:-${CDROM_ROOT}}"
 }
 
 # @FUNCTION: _cdrom_glob_match
-- 
2.55.0