rdsquashfs: reorder unpack flags, add flag to produce listing

The listing command has been used successfully to do the following:

 - generate a prestine file system using gensquashfs
 - repeate multiple times:
   - generate a listing from the file system
   - unpack only the regular files from the file system
   - generate a new file system from the listing
   - run `diff` on the old and new filesystem and admire that they
     are identical
   - replace the old file system with the new one, since they are
     identical

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 73 insertions, 0 deletions

diff --git a/unpack/describe.c b/unpack/describe.c
new file mode 100644
index 0000000..94e7d22
--- /dev/null
+++ b/unpack/describe.c
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "rdsquashfs.h"
+
+#include <sys/sysmacros.h>
+
+static void print_name(tree_node_t *n)
+{
+	if (n->parent != NULL) {
+		print_name(n->parent);
+		fputc('/', stdout);
+	}
+
+	fputs(n->name, stdout);
+}
+
+static void print_perm(tree_node_t *n)
+{
+	printf(" 0%o %d %d", n->mode & (~S_IFMT), n->uid, n->gid);
+}
+
+static void print_simple(const char *type, tree_node_t *n, const char *extra)
+{
+	printf("%s ", type);
+	print_name(n);
+	print_perm(n);
+	if (extra != NULL)
+		printf(" %s", extra);
+	fputc('\n', stdout);
+}
+
+void describe_tree(tree_node_t *root, const char *unpack_root)
+{
+	tree_node_t *n;
+
+	switch (root->mode & S_IFMT) {
+	case S_IFSOCK:
+		print_simple("sock", root, NULL);
+		break;
+	case S_IFLNK:
+		print_simple("slink", root, root->data.slink_target);
+		break;
+	case S_IFIFO:
+		print_simple("pipe", root, NULL);
+		break;
+	case S_IFREG:
+		if (unpack_root != NULL) {
+			fputs("file ", stdout);
+			print_name(root);
+			print_perm(root);
+			printf(" %s", unpack_root);
+			print_name(root);
+			fputc('\n', stdout);
+		} else {
+			print_simple("file", root, NULL);
+		}
+		break;
+	case S_IFCHR:
+	case S_IFBLK: {
+		char buffer[32];
+		sprintf(buffer, "%c %d %d", S_ISCHR(root->mode) ? 'c' : 'b',
+		       major(root->data.devno), minor(root->data.devno));
+		print_simple("nod", root, buffer);
+		break;
+	}
+	case S_IFDIR:
+		if (root->name[0] != '\0')
+			print_simple("dir", root, NULL);
+
+		for (n = root->data.dir->children; n != NULL; n = n->next)
+			describe_tree(n, unpack_root);
+		break;
+	}
+}