Cleanup: try to split sqfs2tar.c in a reasonable way

This comit breaks sqfs2tar into multiple files:
 - options.c contains the command line argument processing
 - write_tree.c contains the code for generating the actual tar archive
 - sqfs2tar.c contains what is left
 - A header is added for glueing it all together.

No actual code is changed.

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

6 files changed, 744 insertions, 689 deletions

diff --git a/bin/Makemodule.am b/bin/Makemodule.am
index 778636c..3e32308 100644
--- a/bin/Makemodule.am
+++ b/bin/Makemodule.am
@@ -1,4 +1,5 @@
-sqfs2tar_SOURCES = bin/sqfs2tar.c
+sqfs2tar_SOURCES = bin/sqfs2tar/sqfs2tar.c bin/sqfs2tar/sqfs2tar.h
+sqfs2tar_SOURCES += bin/sqfs2tar/options.c bin/sqfs2tar/write_tree.c
 sqfs2tar_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
 sqfs2tar_LDADD = libcommon.a libutil.a libsquashfs.la libtar.a libcompat.a
 sqfs2tar_LDADD += libfstree.a $(LZO_LIBS) $(PTHREAD_LIBS)
diff --git a/bin/sqfs2tar.c b/bin/sqfs2tar.c
deleted file mode 100644
index 6d2a51a..0000000
--- a/bin/sqfs2tar.c
+++ /dev/null
@@ -1,688 +0,0 @@
-/* SPDX-License-Identifier: GPL-3.0-or-later */
-/*
- * sqfs2tar.c
- *
- * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
- */
-#include "config.h"
-#include "common.h"
-#include "tar.h"
-
-#include <getopt.h>
-#include <string.h>
-#include <stdlib.h>
-#include <assert.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <stdio.h>
-
-static struct option long_opts[] = {
-	{ "subdir", required_argument, NULL, 'd' },
-	{ "keep-as-dir", no_argument, NULL, 'k' },
-	{ "root-becomes", required_argument, NULL, 'r' },
-	{ "no-skip", no_argument, NULL, 's' },
-	{ "no-xattr", no_argument, NULL, 'X' },
-	{ "no-hard-links", no_argument, NULL, 'L' },
-	{ "help", no_argument, NULL, 'h' },
-	{ "version", no_argument, NULL, 'V' },
-	{ NULL, 0, NULL, 0 },
-};
-
-static const char *short_opts = "d:kr:sXLhV";
-
-static const char *usagestr =
-"Usage: sqfs2tar [OPTIONS...] <sqfsfile>\n"
-"\n"
-"Read an input squashfs archive and turn it into a tar archive, written\n"
-"to stdout.\n"
-"\n"
-"Possible options:\n"
-"\n"
-"  --subdir, -d <dir>        Unpack the given sub directory instead of the\n"
-"                            filesystem root. Can be specified more than\n"
-"                            once to select multiple directories. If only\n"
-"                            one is specified, it becomes the new root of\n"
-"                            node of the archive file system tree.\n"
-"\n"
-"  --root-becomes, -r <dir>  Turn the root inode into a directory with the\n"
-"                            specified name. Everything else will be stored\n"
-"                            inside this directory. The special value '.' is\n"
-"                            allowed to prefix all tar paths with './' and\n"
-"                            add an entry named '.' for the root inode.\n"
-"                            If this option isn't used, all meta data stored\n"
-"                            in the root inode IS LOST!\n"
-"\n"
-"  --keep-as-dir, -k         If --subdir is used only once, don't make the\n"
-"                            subdir the archive root, instead keep it as\n"
-"                            prefix for all unpacked files.\n"
-"                            Using --subdir more than once implies\n"
-"                            --keep-as-dir.\n"
-"  --no-xattr, -X            Do not copy extended attributes.\n"
-"  --no-hard-links, -L       Do not generate hard links. Produce duplicate\n"
-"                            entries instead.\n"
-"\n"
-"  --no-skip, -s             Abort if a file cannot be stored in a tar\n"
-"                            archive. By default, it is simply skipped\n"
-"                            and a warning is written to stderr.\n"
-"\n"
-"  --help, -h                Print help text and exit.\n"
-"  --version, -V             Print version information and exit.\n"
-"\n"
-"Examples:\n"
-"\n"
-"\tsqfs2tar rootfs.sqfs > rootfs.tar\n"
-"\tsqfs2tar rootfs.sqfs | gzip > rootfs.tar.gz\n"
-"\tsqfs2tar rootfs.sqfs | xz > rootfs.tar.xz\n"
-"\n";
-
-static const char *filename;
-static unsigned int record_counter;
-static bool dont_skip = false;
-static bool keep_as_dir = false;
-static bool no_xattr = false;
-static bool no_links = false;
-
-static char *root_becomes = NULL;
-static char **subdirs = NULL;
-static size_t num_subdirs = 0;
-static size_t max_subdirs = 0;
-
-static sqfs_xattr_reader_t *xr;
-static sqfs_data_reader_t *data;
-static sqfs_file_t *file;
-static sqfs_super_t super;
-static sqfs_hard_link_t *links = NULL;
-
-static FILE *out_file = NULL;
-
-static void process_args(int argc, char **argv)
-{
-	size_t idx, new_count;
-	int i, ret;
-	void *new;
-
-	for (;;) {
-		i = getopt_long(argc, argv, short_opts, long_opts, NULL);
-		if (i == -1)
-			break;
-
-		switch (i) {
-		case 'd':
-			if (num_subdirs == max_subdirs) {
-				new_count = max_subdirs ? max_subdirs * 2 : 16;
-				new = realloc(subdirs,
-					      new_count * sizeof(subdirs[0]));
-				if (new == NULL)
-					goto fail_errno;
-
-				max_subdirs = new_count;
-				subdirs = new;
-			}
-
-			subdirs[num_subdirs] = strdup(optarg);
-			if (subdirs[num_subdirs] == NULL)
-				goto fail_errno;
-
-			if (canonicalize_name(subdirs[num_subdirs])) {
-				perror(optarg);
-				goto fail;
-			}
-
-			++num_subdirs;
-			break;
-		case 'r':
-			free(root_becomes);
-			root_becomes = strdup(optarg);
-			if (root_becomes == NULL)
-				goto fail_errno;
-
-			if (strcmp(root_becomes, "./") == 0)
-				root_becomes[1] = '\0';
-
-			if (strcmp(root_becomes, ".") == 0)
-				break;
-
-			if (canonicalize_name(root_becomes) != 0 ||
-			    strlen(root_becomes) == 0) {
-				fprintf(stderr,
-					"Invalid root directory '%s'.\n",
-					optarg);
-				goto fail_arg;
-			}
-			break;
-		case 'k':
-			keep_as_dir = true;
-			break;
-		case 's':
-			dont_skip = true;
-			break;
-		case 'X':
-			no_xattr = true;
-			break;
-		case 'L':
-			no_links = true;
-			break;
-		case 'h':
-			fputs(usagestr, stdout);
-			goto out_success;
-		case 'V':
-			print_version("sqfs2tar");
-			goto out_success;
-		default:
-			goto fail_arg;
-		}
-	}
-
-	if (optind >= argc) {
-		fputs("Missing argument: squashfs image\n", stderr);
-		goto fail_arg;
-	}
-
-	filename = argv[optind++];
-
-	if (optind < argc) {
-		fputs("Unknown extra arguments\n", stderr);
-		goto fail_arg;
-	}
-
-	if (num_subdirs > 1)
-		keep_as_dir = true;
-
-	return;
-fail_errno:
-	perror("parsing options");
-	goto fail;
-fail_arg:
-	fputs("Try `sqfs2tar --help' for more information.\n", stderr);
-	goto fail;
-fail:
-	ret = EXIT_FAILURE;
-	goto out_exit;
-out_success:
-	ret = EXIT_SUCCESS;
-	goto out_exit;
-out_exit:
-	for (idx = 0; idx < num_subdirs; ++idx)
-		free(subdirs[idx]);
-	free(root_becomes);
-	free(subdirs);
-	exit(ret);
-}
-
-static int terminate_archive(void)
-{
-	char buffer[1024];
-
-	memset(buffer, '\0', sizeof(buffer));
-
-	return write_retry("adding archive terminator", out_file,
-			   buffer, sizeof(buffer));
-}
-
-static int get_xattrs(const char *name, const sqfs_inode_generic_t *inode,
-		      tar_xattr_t **out)
-{
-	tar_xattr_t *list = NULL, *ent;
-	sqfs_xattr_value_t *value;
-	sqfs_xattr_entry_t *key;
-	sqfs_xattr_id_t desc;
-	sqfs_u32 index;
-	size_t i;
-	int ret;
-
-	if (xr == NULL)
-		return 0;
-
-	sqfs_inode_get_xattr_index(inode, &index);
-
-	if (index == 0xFFFFFFFF)
-		return 0;
-
-	ret = sqfs_xattr_reader_get_desc(xr, index, &desc);
-	if (ret) {
-		sqfs_perror(name, "resolving xattr index", ret);
-		return -1;
-	}
-
-	ret = sqfs_xattr_reader_seek_kv(xr, &desc);
-	if (ret) {
-		sqfs_perror(name, "locating xattr key-value pairs", ret);
-		return -1;
-	}
-
-	for (i = 0; i < desc.count; ++i) {
-		ret = sqfs_xattr_reader_read_key(xr, &key);
-		if (ret) {
-			sqfs_perror(name, "reading xattr key", ret);
-			goto fail;
-		}
-
-		ret = sqfs_xattr_reader_read_value(xr, key, &value);
-		if (ret) {
-			sqfs_perror(name, "reading xattr value", ret);
-			free(key);
-			goto fail;
-		}
-
-		ent = calloc(1, sizeof(*ent) + strlen((const char *)key->key) +
-			     value->size + 2);
-		if (ent == NULL) {
-			perror("creating xattr entry");
-			free(key);
-			free(value);
-			goto fail;
-		}
-
-		ent->key = ent->data;
-		strcpy(ent->key, (const char *)key->key);
-
-		ent->value = (sqfs_u8 *)ent->key + strlen(ent->key) + 1;
-		memcpy(ent->value, value->value, value->size + 1);
-
-		ent->value_len = value->size;
-		ent->next = list;
-		list = ent;
-
-		free(key);
-		free(value);
-	}
-
-	*out = list;
-	return 0;
-fail:
-	while (list != NULL) {
-		ent = list;
-		list = list->next;
-		free(ent);
-	}
-	return -1;
-}
-
-static char *assemble_tar_path(char *name, bool is_dir)
-{
-	size_t len, new_len;
-	char *temp;
-	(void)is_dir;
-
-	if (root_becomes == NULL && !is_dir)
-		return name;
-
-	new_len = strlen(name);
-	if (root_becomes != NULL)
-		new_len += strlen(root_becomes) + 1;
-	if (is_dir)
-		new_len += 1;
-
-	temp = realloc(name, new_len + 1);
-	if (temp == NULL) {
-		perror("assembling tar entry filename");
-		free(name);
-		return NULL;
-	}
-
-	name = temp;
-
-	if (root_becomes != NULL) {
-		len = strlen(root_becomes);
-
-		memmove(name + len + 1, name, strlen(name) + 1);
-		memcpy(name, root_becomes, len);
-		name[len] = '/';
-	}
-
-	if (is_dir) {
-		len = strlen(name);
-
-		if (len == 0 || name[len - 1] != '/') {
-			name[len++] = '/';
-			name[len] = '\0';
-		}
-	}
-
-	return name;
-}
-
-static int write_tree_dfs(const sqfs_tree_node_t *n)
-{
-	tar_xattr_t *xattr = NULL, *xit;
-	sqfs_hard_link_t *lnk = NULL;
-	char *name, *target;
-	struct stat sb;
-	size_t len;
-	int ret;
-
-	inode_stat(n, &sb);
-
-	if (n->parent == NULL) {
-		if (root_becomes == NULL)
-			goto skip_hdr;
-
-		len = strlen(root_becomes);
-		name = malloc(len + 2);
-		if (name == NULL) {
-			perror("creating root directory");
-			return -1;
-		}
-
-		memcpy(name, root_becomes, len);
-		name[len] = '/';
-		name[len + 1] = '\0';
-	} else {
-		if (!is_filename_sane((const char *)n->name, false)) {
-			fprintf(stderr, "Found a file named '%s', skipping.\n",
-				n->name);
-			if (dont_skip) {
-				fputs("Not allowed to skip files, aborting!\n",
-				      stderr);
-				return -1;
-			}
-			return 0;
-		}
-
-		name = sqfs_tree_node_get_path(n);
-		if (name == NULL) {
-			perror("resolving tree node path");
-			return -1;
-		}
-
-		if (canonicalize_name(name))
-			goto out_skip;
-
-		for (lnk = links; lnk != NULL; lnk = lnk->next) {
-			if (lnk->inode_number == n->inode->base.inode_number) {
-				if (strcmp(name, lnk->target) == 0)
-					lnk = NULL;
-				break;
-			}
-		}
-
-		name = assemble_tar_path(name, S_ISDIR(sb.st_mode));
-		if (name == NULL)
-			return -1;
-	}
-
-	if (lnk != NULL) {
-		ret = write_hard_link(out_file, &sb, name, lnk->target,
-				      record_counter++);
-		free(name);
-		return ret;
-	}
-
-	if (!no_xattr) {
-		if (get_xattrs(name, n->inode, &xattr)) {
-			free(name);
-			return -1;
-		}
-	}
-
-	target = S_ISLNK(sb.st_mode) ? (char *)n->inode->extra : NULL;
-	ret = write_tar_header(out_file, &sb, name, target, xattr,
-			       record_counter++);
-
-	while (xattr != NULL) {
-		xit = xattr;
-		xattr = xattr->next;
-		free(xit);
-	}
-
-	if (ret > 0)
-		goto out_skip;
-
-	if (ret < 0) {
-		free(name);
-		return -1;
-	}
-
-	if (S_ISREG(sb.st_mode)) {
-		if (sqfs_data_reader_dump(name, data, n->inode, out_file,
-					  super.block_size, false)) {
-			free(name);
-			return -1;
-		}
-
-		if (padd_file(out_file, sb.st_size)) {
-			free(name);
-			return -1;
-		}
-	}
-
-	free(name);
-skip_hdr:
-	for (n = n->children; n != NULL; n = n->next) {
-		if (write_tree_dfs(n))
-			return -1;
-	}
-	return 0;
-out_skip:
-	if (dont_skip) {
-		fputs("Not allowed to skip files, aborting!\n", stderr);
-		ret = -1;
-	} else {
-		fprintf(stderr, "Skipping %s\n", name);
-		ret = 0;
-	}
-	free(name);
-	return ret;
-}
-
-static sqfs_tree_node_t *tree_merge(sqfs_tree_node_t *lhs,
-				    sqfs_tree_node_t *rhs)
-{
-	sqfs_tree_node_t *head = NULL, **next_ptr = &head;
-	sqfs_tree_node_t *it, *l, *r;
-	int diff;
-
-	while (lhs->children != NULL && rhs->children != NULL) {
-		diff = strcmp((const char *)lhs->children->name,
-			      (const char *)rhs->children->name);
-
-		if (diff < 0) {
-			it = lhs->children;
-			lhs->children = lhs->children->next;
-		} else if (diff > 0) {
-			it = rhs->children;
-			rhs->children = rhs->children->next;
-		} else {
-			l = lhs->children;
-			lhs->children = lhs->children->next;
-
-			r = rhs->children;
-			rhs->children = rhs->children->next;
-
-			it = tree_merge(l, r);
-		}
-
-		*next_ptr = it;
-		next_ptr = &it->next;
-	}
-
-	it = (lhs->children != NULL ? lhs->children : rhs->children);
-	*next_ptr = it;
-
-	sqfs_dir_tree_destroy(rhs);
-	lhs->children = head;
-	return lhs;
-}
-
-int main(int argc, char **argv)
-{
-	sqfs_tree_node_t *root = NULL, *subtree;
-	int flags, ret, status = EXIT_FAILURE;
-	sqfs_compressor_config_t cfg;
-	sqfs_compressor_t *cmp;
-	sqfs_id_table_t *idtbl;
-	sqfs_dir_reader_t *dr;
-	sqfs_hard_link_t *lnk;
-	size_t i;
-
-	process_args(argc, argv);
-
-#ifdef _WIN32
-	_setmode(_fileno(stdout), _O_BINARY);
-	out_file = stdout;
-#else
-	out_file = freopen(NULL, "wb", stdout);
-#endif
-
-	if (out_file == NULL) {
-		perror("changing stdout to binary mode");
-		goto out_dirs;
-	}
-
-	file = sqfs_open_file(filename, SQFS_FILE_OPEN_READ_ONLY);
-	if (file == NULL) {
-		perror(filename);
-		goto out_dirs;
-	}
-
-	ret = sqfs_super_read(&super, file);
-	if (ret) {
-		sqfs_perror(filename, "reading super block", ret);
-		goto out_fd;
-	}
-
-	sqfs_compressor_config_init(&cfg, super.compression_id,
-				    super.block_size,
-				    SQFS_COMP_FLAG_UNCOMPRESS);
-
-	ret = sqfs_compressor_create(&cfg, &cmp);
-
-#ifdef WITH_LZO
-	if (super.compression_id == SQFS_COMP_LZO && ret != 0)
-		ret = lzo_compressor_create(&cfg, &cmp);
-#endif
-
-	if (ret != 0) {
-		sqfs_perror(filename, "creating compressor", ret);
-		goto out_fd;
-	}
-
-	idtbl = sqfs_id_table_create(0);
-
-	if (idtbl == NULL) {
-		perror("creating ID table");
-		goto out_cmp;
-	}
-
-	ret = sqfs_id_table_read(idtbl, file, &super, cmp);
-	if (ret) {
-		sqfs_perror(filename, "loading ID table", ret);
-		goto out_id;
-	}
-
-	data = sqfs_data_reader_create(file, super.block_size, cmp);
-	if (data == NULL) {
-		sqfs_perror(filename, "creating data reader",
-			    SQFS_ERROR_ALLOC);
-		goto out_id;
-	}
-
-	ret = sqfs_data_reader_load_fragment_table(data, &super);
-	if (ret) {
-		sqfs_perror(filename, "loading fragment table", ret);
-		goto out_data;
-	}
-
-	dr = sqfs_dir_reader_create(&super, cmp, file);
-	if (dr == NULL) {
-		sqfs_perror(filename, "creating dir reader",
-			    SQFS_ERROR_ALLOC);
-		goto out_data;
-	}
-
-	if (!no_xattr && !(super.flags & SQFS_FLAG_NO_XATTRS)) {
-		xr = sqfs_xattr_reader_create(0);
-		if (xr == NULL) {
-			sqfs_perror(filename, "creating xattr reader",
-				    SQFS_ERROR_ALLOC);
-			goto out_dr;
-		}
-
-		ret = sqfs_xattr_reader_load(xr, &super, file, cmp);
-		if (ret) {
-			sqfs_perror(filename, "loading xattr table", ret);
-			goto out_xr;
-		}
-	}
-
-	if (num_subdirs == 0) {
-		ret = sqfs_dir_reader_get_full_hierarchy(dr, idtbl, NULL,
-							 0, &root);
-		if (ret) {
-			sqfs_perror(filename, "loading filesystem tree", ret);
-			goto out;
-		}
-	} else {
-		flags = 0;
-
-		if (keep_as_dir || num_subdirs > 1)
-			flags = SQFS_TREE_STORE_PARENTS;
-
-		for (i = 0; i < num_subdirs; ++i) {
-			ret = sqfs_dir_reader_get_full_hierarchy(dr, idtbl,
-								 subdirs[i],
-								 flags,
-								 &subtree);
-			if (ret) {
-				sqfs_perror(subdirs[i], "loading filesystem "
-					    "tree", ret);
-				goto out;
-			}
-
-			if (root == NULL) {
-				root = subtree;
-			} else {
-				root = tree_merge(root, subtree);
-			}
-		}
-	}
-
-	if (!no_links) {
-		if (sqfs_tree_find_hard_links(root, &links))
-			goto out_tree;
-
-		for (lnk = links; lnk != NULL; lnk = lnk->next) {
-			lnk->target = assemble_tar_path(lnk->target, false);
-			if (lnk->target == NULL)
-				goto out;
-		}
-	}
-
-	if (write_tree_dfs(root))
-		goto out;
-
-	if (terminate_archive())
-		goto out;
-
-	status = EXIT_SUCCESS;
-	fflush(out_file);
-out:
-	while (links != NULL) {
-		lnk = links;
-		links = links->next;
-		free(lnk->target);
-		free(lnk);
-	}
-out_tree:
-	if (root != NULL)
-		sqfs_dir_tree_destroy(root);
-out_xr:
-	if (xr != NULL)
-		sqfs_destroy(xr);
-out_dr:
-	sqfs_destroy(dr);
-out_data:
-	sqfs_destroy(data);
-out_id:
-	sqfs_destroy(idtbl);
-out_cmp:
-	sqfs_destroy(cmp);
-out_fd:
-	sqfs_destroy(file);
-out_dirs:
-	for (i = 0; i < num_subdirs; ++i)
-		free(subdirs[i]);
-	free(subdirs);
-	free(root_becomes);
-	return status;
-}
diff --git a/bin/sqfs2tar/options.c b/bin/sqfs2tar/options.c
new file mode 100644
index 0000000..e5c8319
--- /dev/null
+++ b/bin/sqfs2tar/options.c
@@ -0,0 +1,192 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * options.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "sqfs2tar.h"
+
+static struct option long_opts[] = {
+	{ "subdir", required_argument, NULL, 'd' },
+	{ "keep-as-dir", no_argument, NULL, 'k' },
+	{ "root-becomes", required_argument, NULL, 'r' },
+	{ "no-skip", no_argument, NULL, 's' },
+	{ "no-xattr", no_argument, NULL, 'X' },
+	{ "no-hard-links", no_argument, NULL, 'L' },
+	{ "help", no_argument, NULL, 'h' },
+	{ "version", no_argument, NULL, 'V' },
+	{ NULL, 0, NULL, 0 },
+};
+
+static const char *short_opts = "d:kr:sXLhV";
+
+static const char *usagestr =
+"Usage: sqfs2tar [OPTIONS...] <sqfsfile>\n"
+"\n"
+"Read an input squashfs archive and turn it into a tar archive, written\n"
+"to stdout.\n"
+"\n"
+"Possible options:\n"
+"\n"
+"  --subdir, -d <dir>        Unpack the given sub directory instead of the\n"
+"                            filesystem root. Can be specified more than\n"
+"                            once to select multiple directories. If only\n"
+"                            one is specified, it becomes the new root of\n"
+"                            node of the archive file system tree.\n"
+"\n"
+"  --root-becomes, -r <dir>  Turn the root inode into a directory with the\n"
+"                            specified name. Everything else will be stored\n"
+"                            inside this directory. The special value '.' is\n"
+"                            allowed to prefix all tar paths with './' and\n"
+"                            add an entry named '.' for the root inode.\n"
+"                            If this option isn't used, all meta data stored\n"
+"                            in the root inode IS LOST!\n"
+"\n"
+"  --keep-as-dir, -k         If --subdir is used only once, don't make the\n"
+"                            subdir the archive root, instead keep it as\n"
+"                            prefix for all unpacked files.\n"
+"                            Using --subdir more than once implies\n"
+"                            --keep-as-dir.\n"
+"  --no-xattr, -X            Do not copy extended attributes.\n"
+"  --no-hard-links, -L       Do not generate hard links. Produce duplicate\n"
+"                            entries instead.\n"
+"\n"
+"  --no-skip, -s             Abort if a file cannot be stored in a tar\n"
+"                            archive. By default, it is simply skipped\n"
+"                            and a warning is written to stderr.\n"
+"\n"
+"  --help, -h                Print help text and exit.\n"
+"  --version, -V             Print version information and exit.\n"
+"\n"
+"Examples:\n"
+"\n"
+"\tsqfs2tar rootfs.sqfs > rootfs.tar\n"
+"\tsqfs2tar rootfs.sqfs | gzip > rootfs.tar.gz\n"
+"\tsqfs2tar rootfs.sqfs | xz > rootfs.tar.xz\n"
+"\n";
+
+bool dont_skip = false;
+bool keep_as_dir = false;
+bool no_xattr = false;
+bool no_links = false;
+
+char *root_becomes = NULL;
+char **subdirs = NULL;
+size_t num_subdirs = 0;
+static size_t max_subdirs = 0;
+
+const char *filename = NULL;
+
+void process_args(int argc, char **argv)
+{
+	size_t idx, new_count;
+	int i, ret;
+	void *new;
+
+	for (;;) {
+		i = getopt_long(argc, argv, short_opts, long_opts, NULL);
+		if (i == -1)
+			break;
+
+		switch (i) {
+		case 'd':
+			if (num_subdirs == max_subdirs) {
+				new_count = max_subdirs ? max_subdirs * 2 : 16;
+				new = realloc(subdirs,
+					      new_count * sizeof(subdirs[0]));
+				if (new == NULL)
+					goto fail_errno;
+
+				max_subdirs = new_count;
+				subdirs = new;
+			}
+
+			subdirs[num_subdirs] = strdup(optarg);
+			if (subdirs[num_subdirs] == NULL)
+				goto fail_errno;
+
+			if (canonicalize_name(subdirs[num_subdirs])) {
+				perror(optarg);
+				goto fail;
+			}
+
+			++num_subdirs;
+			break;
+		case 'r':
+			free(root_becomes);
+			root_becomes = strdup(optarg);
+			if (root_becomes == NULL)
+				goto fail_errno;
+
+			if (strcmp(root_becomes, "./") == 0)
+				root_becomes[1] = '\0';
+
+			if (strcmp(root_becomes, ".") == 0)
+				break;
+
+			if (canonicalize_name(root_becomes) != 0 ||
+			    strlen(root_becomes) == 0) {
+				fprintf(stderr,
+					"Invalid root directory '%s'.\n",
+					optarg);
+				goto fail_arg;
+			}
+			break;
+		case 'k':
+			keep_as_dir = true;
+			break;
+		case 's':
+			dont_skip = true;
+			break;
+		case 'X':
+			no_xattr = true;
+			break;
+		case 'L':
+			no_links = true;
+			break;
+		case 'h':
+			fputs(usagestr, stdout);
+			goto out_success;
+		case 'V':
+			print_version("sqfs2tar");
+			goto out_success;
+		default:
+			goto fail_arg;
+		}
+	}
+
+	if (optind >= argc) {
+		fputs("Missing argument: squashfs image\n", stderr);
+		goto fail_arg;
+	}
+
+	filename = argv[optind++];
+
+	if (optind < argc) {
+		fputs("Unknown extra arguments\n", stderr);
+		goto fail_arg;
+	}
+
+	if (num_subdirs > 1)
+		keep_as_dir = true;
+
+	return;
+fail_errno:
+	perror("parsing options");
+	goto fail;
+fail_arg:
+	fputs("Try `sqfs2tar --help' for more information.\n", stderr);
+	goto fail;
+fail:
+	ret = EXIT_FAILURE;
+	goto out_exit;
+out_success:
+	ret = EXIT_SUCCESS;
+	goto out_exit;
+out_exit:
+	for (idx = 0; idx < num_subdirs; ++idx)
+		free(subdirs[idx]);
+	free(root_becomes);
+	free(subdirs);
+	exit(ret);
+}
diff --git a/bin/sqfs2tar/sqfs2tar.c b/bin/sqfs2tar/sqfs2tar.c
new file mode 100644
index 0000000..305bd4b
--- /dev/null
+++ b/bin/sqfs2tar/sqfs2tar.c
@@ -0,0 +1,291 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * sqfs2tar.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "sqfs2tar.h"
+
+sqfs_xattr_reader_t *xr;
+sqfs_data_reader_t *data;
+sqfs_super_t super;
+sqfs_hard_link_t *links = NULL;
+FILE *out_file = NULL;
+
+static sqfs_file_t *file;
+
+char *assemble_tar_path(char *name, bool is_dir)
+{
+	size_t len, new_len;
+	char *temp;
+	(void)is_dir;
+
+	if (root_becomes == NULL && !is_dir)
+		return name;
+
+	new_len = strlen(name);
+	if (root_becomes != NULL)
+		new_len += strlen(root_becomes) + 1;
+	if (is_dir)
+		new_len += 1;
+
+	temp = realloc(name, new_len + 1);
+	if (temp == NULL) {
+		perror("assembling tar entry filename");
+		free(name);
+		return NULL;
+	}
+
+	name = temp;
+
+	if (root_becomes != NULL) {
+		len = strlen(root_becomes);
+
+		memmove(name + len + 1, name, strlen(name) + 1);
+		memcpy(name, root_becomes, len);
+		name[len] = '/';
+	}
+
+	if (is_dir) {
+		len = strlen(name);
+
+		if (len == 0 || name[len - 1] != '/') {
+			name[len++] = '/';
+			name[len] = '\0';
+		}
+	}
+
+	return name;
+}
+
+static int terminate_archive(void)
+{
+	char buffer[1024];
+
+	memset(buffer, '\0', sizeof(buffer));
+
+	return write_retry("adding archive terminator", out_file,
+			   buffer, sizeof(buffer));
+}
+
+static sqfs_tree_node_t *tree_merge(sqfs_tree_node_t *lhs,
+				    sqfs_tree_node_t *rhs)
+{
+	sqfs_tree_node_t *head = NULL, **next_ptr = &head;
+	sqfs_tree_node_t *it, *l, *r;
+	int diff;
+
+	while (lhs->children != NULL && rhs->children != NULL) {
+		diff = strcmp((const char *)lhs->children->name,
+			      (const char *)rhs->children->name);
+
+		if (diff < 0) {
+			it = lhs->children;
+			lhs->children = lhs->children->next;
+		} else if (diff > 0) {
+			it = rhs->children;
+			rhs->children = rhs->children->next;
+		} else {
+			l = lhs->children;
+			lhs->children = lhs->children->next;
+
+			r = rhs->children;
+			rhs->children = rhs->children->next;
+
+			it = tree_merge(l, r);
+		}
+
+		*next_ptr = it;
+		next_ptr = &it->next;
+	}
+
+	it = (lhs->children != NULL ? lhs->children : rhs->children);
+	*next_ptr = it;
+
+	sqfs_dir_tree_destroy(rhs);
+	lhs->children = head;
+	return lhs;
+}
+
+int main(int argc, char **argv)
+{
+	sqfs_tree_node_t *root = NULL, *subtree;
+	int flags, ret, status = EXIT_FAILURE;
+	sqfs_compressor_config_t cfg;
+	sqfs_compressor_t *cmp;
+	sqfs_id_table_t *idtbl;
+	sqfs_dir_reader_t *dr;
+	sqfs_hard_link_t *lnk;
+	size_t i;
+
+	process_args(argc, argv);
+
+#ifdef _WIN32
+	_setmode(_fileno(stdout), _O_BINARY);
+	out_file = stdout;
+#else
+	out_file = freopen(NULL, "wb", stdout);
+#endif
+
+	if (out_file == NULL) {
+		perror("changing stdout to binary mode");
+		goto out_dirs;
+	}
+
+	file = sqfs_open_file(filename, SQFS_FILE_OPEN_READ_ONLY);
+	if (file == NULL) {
+		perror(filename);
+		goto out_dirs;
+	}
+
+	ret = sqfs_super_read(&super, file);
+	if (ret) {
+		sqfs_perror(filename, "reading super block", ret);
+		goto out_fd;
+	}
+
+	sqfs_compressor_config_init(&cfg, super.compression_id,
+				    super.block_size,
+				    SQFS_COMP_FLAG_UNCOMPRESS);
+
+	ret = sqfs_compressor_create(&cfg, &cmp);
+
+#ifdef WITH_LZO
+	if (super.compression_id == SQFS_COMP_LZO && ret != 0)
+		ret = lzo_compressor_create(&cfg, &cmp);
+#endif
+
+	if (ret != 0) {
+		sqfs_perror(filename, "creating compressor", ret);
+		goto out_fd;
+	}
+
+	idtbl = sqfs_id_table_create(0);
+
+	if (idtbl == NULL) {
+		perror("creating ID table");
+		goto out_cmp;
+	}
+
+	ret = sqfs_id_table_read(idtbl, file, &super, cmp);
+	if (ret) {
+		sqfs_perror(filename, "loading ID table", ret);
+		goto out_id;
+	}
+
+	data = sqfs_data_reader_create(file, super.block_size, cmp);
+	if (data == NULL) {
+		sqfs_perror(filename, "creating data reader",
+			    SQFS_ERROR_ALLOC);
+		goto out_id;
+	}
+
+	ret = sqfs_data_reader_load_fragment_table(data, &super);
+	if (ret) {
+		sqfs_perror(filename, "loading fragment table", ret);
+		goto out_data;
+	}
+
+	dr = sqfs_dir_reader_create(&super, cmp, file);
+	if (dr == NULL) {
+		sqfs_perror(filename, "creating dir reader",
+			    SQFS_ERROR_ALLOC);
+		goto out_data;
+	}
+
+	if (!no_xattr && !(super.flags & SQFS_FLAG_NO_XATTRS)) {
+		xr = sqfs_xattr_reader_create(0);
+		if (xr == NULL) {
+			sqfs_perror(filename, "creating xattr reader",
+				    SQFS_ERROR_ALLOC);
+			goto out_dr;
+		}
+
+		ret = sqfs_xattr_reader_load(xr, &super, file, cmp);
+		if (ret) {
+			sqfs_perror(filename, "loading xattr table", ret);
+			goto out_xr;
+		}
+	}
+
+	if (num_subdirs == 0) {
+		ret = sqfs_dir_reader_get_full_hierarchy(dr, idtbl, NULL,
+							 0, &root);
+		if (ret) {
+			sqfs_perror(filename, "loading filesystem tree", ret);
+			goto out;
+		}
+	} else {
+		flags = 0;
+
+		if (keep_as_dir || num_subdirs > 1)
+			flags = SQFS_TREE_STORE_PARENTS;
+
+		for (i = 0; i < num_subdirs; ++i) {
+			ret = sqfs_dir_reader_get_full_hierarchy(dr, idtbl,
+								 subdirs[i],
+								 flags,
+								 &subtree);
+			if (ret) {
+				sqfs_perror(subdirs[i], "loading filesystem "
+					    "tree", ret);
+				goto out;
+			}
+
+			if (root == NULL) {
+				root = subtree;
+			} else {
+				root = tree_merge(root, subtree);
+			}
+		}
+	}
+
+	if (!no_links) {
+		if (sqfs_tree_find_hard_links(root, &links))
+			goto out_tree;
+
+		for (lnk = links; lnk != NULL; lnk = lnk->next) {
+			lnk->target = assemble_tar_path(lnk->target, false);
+			if (lnk->target == NULL)
+				goto out;
+		}
+	}
+
+	if (write_tree_dfs(root))
+		goto out;
+
+	if (terminate_archive())
+		goto out;
+
+	status = EXIT_SUCCESS;
+	fflush(out_file);
+out:
+	while (links != NULL) {
+		lnk = links;
+		links = links->next;
+		free(lnk->target);
+		free(lnk);
+	}
+out_tree:
+	if (root != NULL)
+		sqfs_dir_tree_destroy(root);
+out_xr:
+	if (xr != NULL)
+		sqfs_destroy(xr);
+out_dr:
+	sqfs_destroy(dr);
+out_data:
+	sqfs_destroy(data);
+out_id:
+	sqfs_destroy(idtbl);
+out_cmp:
+	sqfs_destroy(cmp);
+out_fd:
+	sqfs_destroy(file);
+out_dirs:
+	for (i = 0; i < num_subdirs; ++i)
+		free(subdirs[i]);
+	free(subdirs);
+	free(root_becomes);
+	return status;
+}
diff --git a/bin/sqfs2tar/sqfs2tar.h b/bin/sqfs2tar/sqfs2tar.h
new file mode 100644
index 0000000..afd267e
--- /dev/null
+++ b/bin/sqfs2tar/sqfs2tar.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * sqfs2tar.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef SQFS2TAR_H
+#define SQFS2TAR_H
+
+#include "config.h"
+#include "common.h"
+#include "tar.h"
+
+#include <getopt.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+/* options.c */
+extern bool dont_skip;
+extern bool keep_as_dir;
+extern bool no_xattr;
+extern bool no_links;
+
+extern char *root_becomes;
+extern char **subdirs;
+extern size_t num_subdirs;
+
+extern const char *filename;
+
+void process_args(int argc, char **argv);
+
+/* tar2sqfs.c */
+extern sqfs_xattr_reader_t *xr;
+extern sqfs_data_reader_t *data;
+extern sqfs_super_t super;
+extern sqfs_hard_link_t *links;
+extern FILE *out_file;
+
+char *assemble_tar_path(char *name, bool is_dir);
+
+/* write_tree.c */
+int write_tree_dfs(const sqfs_tree_node_t *n);
+
+#endif /* SQFS2TAR_H */
diff --git a/bin/sqfs2tar/write_tree.c b/bin/sqfs2tar/write_tree.c
new file mode 100644
index 0000000..545adc1
--- /dev/null
+++ b/bin/sqfs2tar/write_tree.c
@@ -0,0 +1,211 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * write_tree.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "sqfs2tar.h"
+
+static unsigned int record_counter;
+
+static int get_xattrs(const char *name, const sqfs_inode_generic_t *inode,
+		      tar_xattr_t **out)
+{
+	tar_xattr_t *list = NULL, *ent;
+	sqfs_xattr_value_t *value;
+	sqfs_xattr_entry_t *key;
+	sqfs_xattr_id_t desc;
+	sqfs_u32 index;
+	size_t i;
+	int ret;
+
+	if (xr == NULL)
+		return 0;
+
+	sqfs_inode_get_xattr_index(inode, &index);
+
+	if (index == 0xFFFFFFFF)
+		return 0;
+
+	ret = sqfs_xattr_reader_get_desc(xr, index, &desc);
+	if (ret) {
+		sqfs_perror(name, "resolving xattr index", ret);
+		return -1;
+	}
+
+	ret = sqfs_xattr_reader_seek_kv(xr, &desc);
+	if (ret) {
+		sqfs_perror(name, "locating xattr key-value pairs", ret);
+		return -1;
+	}
+
+	for (i = 0; i < desc.count; ++i) {
+		ret = sqfs_xattr_reader_read_key(xr, &key);
+		if (ret) {
+			sqfs_perror(name, "reading xattr key", ret);
+			goto fail;
+		}
+
+		ret = sqfs_xattr_reader_read_value(xr, key, &value);
+		if (ret) {
+			sqfs_perror(name, "reading xattr value", ret);
+			free(key);
+			goto fail;
+		}
+
+		ent = calloc(1, sizeof(*ent) + strlen((const char *)key->key) +
+			     value->size + 2);
+		if (ent == NULL) {
+			perror("creating xattr entry");
+			free(key);
+			free(value);
+			goto fail;
+		}
+
+		ent->key = ent->data;
+		strcpy(ent->key, (const char *)key->key);
+
+		ent->value = (sqfs_u8 *)ent->key + strlen(ent->key) + 1;
+		memcpy(ent->value, value->value, value->size + 1);
+
+		ent->value_len = value->size;
+		ent->next = list;
+		list = ent;
+
+		free(key);
+		free(value);
+	}
+
+	*out = list;
+	return 0;
+fail:
+	while (list != NULL) {
+		ent = list;
+		list = list->next;
+		free(ent);
+	}
+	return -1;
+}
+
+int write_tree_dfs(const sqfs_tree_node_t *n)
+{
+	tar_xattr_t *xattr = NULL, *xit;
+	sqfs_hard_link_t *lnk = NULL;
+	char *name, *target;
+	struct stat sb;
+	size_t len;
+	int ret;
+
+	inode_stat(n, &sb);
+
+	if (n->parent == NULL) {
+		if (root_becomes == NULL)
+			goto skip_hdr;
+
+		len = strlen(root_becomes);
+		name = malloc(len + 2);
+		if (name == NULL) {
+			perror("creating root directory");
+			return -1;
+		}
+
+		memcpy(name, root_becomes, len);
+		name[len] = '/';
+		name[len + 1] = '\0';
+	} else {
+		if (!is_filename_sane((const char *)n->name, false)) {
+			fprintf(stderr, "Found a file named '%s', skipping.\n",
+				n->name);
+			if (dont_skip) {
+				fputs("Not allowed to skip files, aborting!\n",
+				      stderr);
+				return -1;
+			}
+			return 0;
+		}
+
+		name = sqfs_tree_node_get_path(n);
+		if (name == NULL) {
+			perror("resolving tree node path");
+			return -1;
+		}
+
+		if (canonicalize_name(name))
+			goto out_skip;
+
+		for (lnk = links; lnk != NULL; lnk = lnk->next) {
+			if (lnk->inode_number == n->inode->base.inode_number) {
+				if (strcmp(name, lnk->target) == 0)
+					lnk = NULL;
+				break;
+			}
+		}
+
+		name = assemble_tar_path(name, S_ISDIR(sb.st_mode));
+		if (name == NULL)
+			return -1;
+	}
+
+	if (lnk != NULL) {
+		ret = write_hard_link(out_file, &sb, name, lnk->target,
+				      record_counter++);
+		free(name);
+		return ret;
+	}
+
+	if (!no_xattr) {
+		if (get_xattrs(name, n->inode, &xattr)) {
+			free(name);
+			return -1;
+		}
+	}
+
+	target = S_ISLNK(sb.st_mode) ? (char *)n->inode->extra : NULL;
+	ret = write_tar_header(out_file, &sb, name, target, xattr,
+			       record_counter++);
+
+	while (xattr != NULL) {
+		xit = xattr;
+		xattr = xattr->next;
+		free(xit);
+	}
+
+	if (ret > 0)
+		goto out_skip;
+
+	if (ret < 0) {
+		free(name);
+		return -1;
+	}
+
+	if (S_ISREG(sb.st_mode)) {
+		if (sqfs_data_reader_dump(name, data, n->inode, out_file,
+					  super.block_size, false)) {
+			free(name);
+			return -1;
+		}
+
+		if (padd_file(out_file, sb.st_size)) {
+			free(name);
+			return -1;
+		}
+	}
+
+	free(name);
+skip_hdr:
+	for (n = n->children; n != NULL; n = n->next) {
+		if (write_tree_dfs(n))
+			return -1;
+	}
+	return 0;
+out_skip:
+	if (dont_skip) {
+		fputs("Not allowed to skip files, aborting!\n", stderr);
+		ret = -1;
+	} else {
+		fprintf(stderr, "Skipping %s\n", name);
+		ret = 0;
+	}
+	free(name);
+	return ret;
+}