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>

5 files changed, 139 insertions, 48 deletions

diff --git a/unpack/Makemodule.am b/unpack/Makemodule.am
index 6a0eab0..d47cb5e 100644
--- a/unpack/Makemodule.am
+++ b/unpack/Makemodule.am
@@ -1,7 +1,7 @@
 rdsquashfs_SOURCES = unpack/rdsquashfs.c unpack/tree_node_from_inode.c
 rdsquashfs_SOURCES += unpack/rdsquashfs.h unpack/read_fstree.c
 rdsquashfs_SOURCES += unpack/list_files.c unpack/extract_file.c
-rdsquashfs_SOURCES += unpack/restore_fstree.c
+rdsquashfs_SOURCES += unpack/restore_fstree.c unpack/describe.c
 rdsquashfs_LDADD = libsquashfs.a libfstree.a libcompress.a libutil.a
 
 if WITH_XZ
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;
+	}
+}
diff --git a/unpack/rdsquashfs.c b/unpack/rdsquashfs.c
index f09847d..a24434c 100644
--- a/unpack/rdsquashfs.c
+++ b/unpack/rdsquashfs.c
@@ -6,18 +6,20 @@ enum {
 	OP_LS,
 	OP_CAT,
 	OP_UNPACK,
+	OP_DESCRIBE,
 };
 
 static struct option long_opts[] = {
 	{ "list", required_argument, NULL, 'l' },
 	{ "cat", required_argument, NULL, 'c' },
-	{ "unpack-root", required_argument, NULL, 'u' },
-	{ "unpack-path", required_argument, NULL, 'p' },
+	{ "unpack-root", required_argument, NULL, 'p' },
+	{ "unpack-path", required_argument, NULL, 'u' },
 	{ "no-dev", no_argument, NULL, 'D' },
 	{ "no-sock", no_argument, NULL, 'S' },
 	{ "no-fifo", no_argument, NULL, 'F' },
 	{ "no-slink", no_argument, NULL, 'L' },
 	{ "no-empty-dir", no_argument, NULL, 'E' },
+	{ "describe", no_argument, NULL, 'd' },
 	{ "chmod", no_argument, NULL, 'C' },
 	{ "chown", no_argument, NULL, 'O' },
 	{ "quiet", no_argument, NULL, 'q' },
@@ -25,7 +27,7 @@ static struct option long_opts[] = {
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "l:c:u:p:DSFLCOEqhV";
+static const char *short_opts = "l:c:u:p:DSFLCOEdqhV";
 
 static const char *help_string =
 "Usage: %s [OPTIONS] <squashfs-file>\n"
@@ -33,27 +35,34 @@ static const char *help_string =
 "View or extract the contents of a squashfs image.\n"
 "\n"
 "Possible options:\n"
-"  --list, -l <path>     Produce a directory listing for a given path in the\n"
-"                        squashfs image.\n"
-"  --cat, -c <path>      If the specified path is a regular file in the,\n"
-"                        image, dump its contents to stdout.\n"
-"  --unpack-root <path>  Unpack the contents of the filesystem into the\n"
-"                        specified path.\n"
-"  --unpack-path <path>  If specified, unpack this sub directory from the\n"
-"                        image instead of the filesystem root.\n"
-"  --no-dev, -D          Do not unpack device special files.\n"
-"  --no-sock, -S         Do not unpack socket files.\n"
-"  --no-fifo, -F         Do not unpack named pipes.\n"
-"  --no-slink, -L        Do not unpack symbolic links.\n"
-"  --no-empty-dir, -E    Do not unpack directories that would end up empty.\n"
-"  --chmod, -C           Change permission flags of unpacked files to those\n"
-"                        store in the squashfs image.\n"
-"  --chown, -O           Change ownership of unpacked files to the UID/GID\n"
-"                        set in the squashfs image.\n"
-"  --quiet, -q           Do not print out progress while unpacking.\n"
 "\n"
-"  --help, -h            Print help text and exit.\n"
-"  --version, -V         Print version information and exit.\n"
+"  --list, -l <path>         Produce a directory listing for a given path in\n"
+"                            the squashfs image.\n"
+"  --cat, -c <path>          If the specified path is a regular file in the,\n"
+"                            image, dump its contents to stdout.\n"
+"  --unpack-path, -u <path>  Unpack this sub directory from the image. To\n"
+"                            unpack everything, simply specify /.\n"
+"  --describe, -d            Produce a file listing from the image.\n"
+"\n"
+"  --unpack-root, -p <path>  If used with --unpack-path, this is where the\n"
+"                            data unpacked to. If used with --describe, this\n"
+"                            is used as a prefix for the input path of\n"
+"                            regular files.\n"
+"\n"
+"  --no-dev, -D              Do not unpack device special files.\n"
+"  --no-sock, -S             Do not unpack socket files.\n"
+"  --no-fifo, -F             Do not unpack named pipes.\n"
+"  --no-slink, -L            Do not unpack symbolic links.\n"
+"  --no-empty-dir, -E        Do not unpack directories that would end up\n"
+"                            empty after applying the above rules.\n"
+"  --chmod, -C               Change permission flags of unpacked files to\n"
+"                            those store in the squashfs image.\n"
+"  --chown, -O               Change ownership of unpacked files to the\n"
+"                            UID/GID set in the squashfs image.\n"
+"  --quiet, -q               Do not print out progress while unpacking.\n"
+"\n"
+"  --help, -h                Print help text and exit.\n"
+"  --version, -V             Print version information and exit.\n"
 "\n";
 
 extern const char *__progname;
@@ -192,15 +201,18 @@ int main(int argc, char **argv)
 			op = OP_CAT;
 			cmdpath = get_path(cmdpath, optarg);
 			break;
+		case 'd':
+			op = OP_DESCRIBE;
+			break;
 		case 'l':
 			op = OP_LS;
 			cmdpath = get_path(cmdpath, optarg);
 			break;
-		case 'u':
-			op = OP_UNPACK;
+		case 'p':
 			unpack_root = optarg;
 			break;
-		case 'p':
+		case 'u':
+			op = OP_UNPACK;
 			cmdpath = get_path(cmdpath, optarg);
 			break;
 		case 'q':
@@ -303,14 +315,10 @@ int main(int argc, char **argv)
 			goto out_fs;
 		break;
 	case OP_UNPACK:
-		if (cmdpath == NULL) {
-			n = fs.root;
-		} else {
-			n = find_node(fs.root, cmdpath);
-			if (n == NULL) {
-				perror(cmdpath);
-				goto out_fs;
-			}
+		n = find_node(fs.root, cmdpath);
+		if (n == NULL) {
+			perror(cmdpath);
+			goto out_fs;
 		}
 
 		if (load_fragment_table(&info, &super))
@@ -322,6 +330,9 @@ int main(int argc, char **argv)
 		if (restore_fstree(unpack_root, n, &info))
 			goto out_fs;
 		break;
+	case OP_DESCRIBE:
+		describe_tree(fs.root, unpack_root);
+		break;
 	}
 
 	status = EXIT_SUCCESS;
diff --git a/unpack/rdsquashfs.h b/unpack/rdsquashfs.h
index a9d5bdf..f1cd131 100644
--- a/unpack/rdsquashfs.h
+++ b/unpack/rdsquashfs.h
@@ -55,4 +55,6 @@ int extract_file(file_info_t *fi, unsqfs_info_t *info, int outfd);
 int restore_fstree(const char *rootdir, tree_node_t *root,
 		   unsqfs_info_t *info);
 
+void describe_tree(tree_node_t *root, const char *unpack_root);
+
 #endif /* RDSQUASHFS_H */
diff --git a/unpack/restore_fstree.c b/unpack/restore_fstree.c
index c1320ea..3e7f500 100644
--- a/unpack/restore_fstree.c
+++ b/unpack/restore_fstree.c
@@ -117,27 +117,32 @@ int restore_fstree(const char *rootdir, tree_node_t *root, unsqfs_info_t *info)
 	if (mkdir_p(rootdir))
 		return -1;
 
-	dirfd = open(rootdir, O_RDONLY | O_DIRECTORY);
-	if (dirfd < 0) {
-		perror(rootdir);
-		return -1;
+	if (rootdir == NULL) {
+		dirfd = AT_FDCWD;
+	} else {
+		dirfd = open(rootdir, O_RDONLY | O_DIRECTORY);
+		if (dirfd < 0) {
+			perror(rootdir);
+			return -1;
+		}
 	}
 
 	if (S_ISDIR(root->mode)) {
 		for (n = root->data.dir->children; n != NULL; n = n->next) {
-			if (create_node(dirfd, n, info)) {
-				close(dirfd);
-				return -1;
-			}
+			if (create_node(dirfd, n, info))
+				goto fail;
 		}
 		return 0;
 	}
 
-	if (create_node(dirfd, root, info)) {
-		close(dirfd);
-		return -1;
-	}
+	if (create_node(dirfd, root, info))
+		goto fail;
 
-	close(dirfd);
+	if (dirfd != AT_FDCWD)
+		close(dirfd);
 	return 0;
+fail:
+	if (dirfd != AT_FDCWD)
+		close(dirfd);
+	return -1;
 }