sqfs2tar: replace hierarchy extraction with nested iterators

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

4 files changed, 499 insertions, 430 deletions

diff --git a/bin/sqfs2tar/src/iterator.c b/bin/sqfs2tar/src/iterator.c
new file mode 100644
index 0000000..42f01e2
--- /dev/null
+++ b/bin/sqfs2tar/src/iterator.c
@@ -0,0 +1,394 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * iterator.c
+ *
+ * Copyright (C) 2023 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "sqfs2tar.h"
+
+enum {
+	STATE_INITIALIZED = 0,
+	STATE_ROOT = 1,
+	STATE_ENTRY = 2,
+	STATE_EOF = 3,
+};
+
+typedef struct {
+	sqfs_dir_iterator_t base;
+
+	sqfs_super_t super;
+
+	sqfs_dir_iterator_t *src;
+	sqfs_inode_generic_t *root;
+	sqfs_xattr_t *root_xattr;
+	sqfs_u32 root_uid;
+	sqfs_u32 root_gid;
+
+	int state;
+} iterator_t;
+
+static sqfs_dir_entry_t *create_root_entry(iterator_t *it)
+{
+	size_t nlen = strlen(root_becomes);
+	sqfs_dir_entry_t *ent = calloc(1, sizeof(*ent) + nlen + 2);
+
+	if (ent == NULL)
+		return NULL;
+
+	memcpy(ent->name, root_becomes, nlen);
+	ent->name[nlen] = '/';
+
+	if (it->root->base.type == SQFS_INODE_EXT_DIR) {
+		ent->size = it->root->data.dir_ext.size;
+	} else {
+		ent->size = it->root->data.dir.size;
+	}
+
+	ent->mtime = it->root->base.mod_time;
+	ent->inode = it->super.root_inode_ref;
+	ent->mode = it->root->base.mode;
+	ent->uid = it->root_uid;
+	ent->gid = it->root_gid;
+	return ent;
+}
+
+static bool keep_entry(const sqfs_dir_entry_t *ent)
+{
+	size_t nlen;
+
+	if (num_subdirs == 0)
+		return true;
+
+	nlen = strlen(ent->name);
+
+	for (size_t i = 0; i < num_subdirs; ++i) {
+		size_t plen = strlen(subdirs[i]);
+
+		if (nlen <= plen) {
+			if ((nlen == plen || subdirs[i][nlen] == '/') &&
+			    strncmp(subdirs[i], ent->name, nlen) == 0) {
+				return true;
+			}
+		} else if (ent->name[plen] == '/' &&
+			   strncmp(subdirs[i], ent->name, plen) == 0) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static void destroy(sqfs_object_t *obj)
+{
+	iterator_t *it = (iterator_t *)obj;
+
+	sqfs_xattr_list_free(it->root_xattr);
+	sqfs_free(it->root);
+	sqfs_drop(it->src);
+	free(it);
+}
+
+static int next(sqfs_dir_iterator_t *base, sqfs_dir_entry_t **out)
+{
+	iterator_t *it = (iterator_t *)base;
+	sqfs_dir_entry_t *ent;
+
+	*out = NULL;
+
+	switch (it->state) {
+	case STATE_INITIALIZED:
+		*out = create_root_entry(it);
+		if (*out == NULL) {
+			it->state = SQFS_ERROR_ALLOC;
+			return SQFS_ERROR_ALLOC;
+		}
+		it->state = STATE_ROOT;
+		return 0;
+	case STATE_ROOT:
+		it->state = STATE_ENTRY;
+		break;
+	case STATE_ENTRY:
+		break;
+	case STATE_EOF:
+		return 1;
+	default:
+		return it->state;
+	}
+
+	for (;;) {
+		int ret = it->src->next(it->src, &ent);
+		if (ret != 0) {
+			it->state = ret < 0 ? ret : STATE_EOF;
+			return ret;
+		}
+
+		if (keep_entry(ent)) {
+			/* XXX: skip the entry, but we MUST recurse here! */
+			if (num_subdirs == 1 && !keep_as_dir &&
+			    strlen(ent->name) <= strlen(subdirs[0])) {
+				sqfs_free(ent);
+				continue;
+			}
+			break;
+		}
+
+		if (S_ISDIR(ent->mode))
+			it->src->ignore_subdir(it->src);
+
+		sqfs_free(ent);
+	}
+
+	if (num_subdirs == 1 && !keep_as_dir) {
+		size_t plen = strlen(subdirs[0]) + 1;
+
+		memmove(ent->name, ent->name + plen,
+			strlen(ent->name + plen) + 1);
+	}
+
+	if (root_becomes != NULL) {
+		size_t nlen = strlen(ent->name);
+		size_t rlen = strlen(root_becomes);
+		void *new = realloc(ent, sizeof(*ent) + nlen + rlen + 2);
+		if (new == NULL)
+			goto fail_alloc;
+
+		ent = new;
+		memmove(ent->name + rlen + 1, ent->name, nlen + 1);
+		memcpy(ent->name, root_becomes, rlen);
+		ent->name[rlen] = '/';
+	}
+
+	if (S_ISDIR(ent->mode)) {
+		size_t nlen = strlen(ent->name);
+		void *new = realloc(ent, sizeof(*ent) + nlen + 2);
+		if (new == NULL)
+			goto fail_alloc;
+
+		ent = new;
+		ent->name[nlen++] = '/';
+		ent->name[nlen  ] = '\0';
+	}
+
+	*out = ent;
+	return 0;
+fail_alloc:
+	sqfs_free(ent);
+	it->state = SQFS_ERROR_ALLOC;
+	return SQFS_ERROR_ALLOC;
+}
+
+static int read_link(sqfs_dir_iterator_t *base, char **out)
+{
+	iterator_t *it = (iterator_t *)base;
+
+	if (it->state != STATE_ENTRY)
+		return it->state < 0 ? it->state : SQFS_ERROR_NO_ENTRY;
+
+	return it->src->read_link(it->src, out);
+}
+
+static int open_file_ro(sqfs_dir_iterator_t *base, sqfs_istream_t **out)
+{
+	iterator_t *it = (iterator_t *)base;
+
+	if (it->state != STATE_ENTRY)
+		return it->state < 0 ? it->state : SQFS_ERROR_NO_ENTRY;
+
+	return it->src->open_file_ro(it->src, out);
+}
+
+static int read_xattr(sqfs_dir_iterator_t *base, sqfs_xattr_t **out)
+{
+	iterator_t *it = (iterator_t *)base;
+
+	if (it->state == STATE_ROOT) {
+		if (it->root_xattr != NULL) {
+			*out = sqfs_xattr_list_copy(it->root_xattr);
+			if (*out == NULL)
+				return SQFS_ERROR_ALLOC;
+		} else {
+			*out = NULL;
+		}
+		return 0;
+	}
+
+	if (it->state != STATE_ENTRY)
+		return it->state < 0 ? it->state : SQFS_ERROR_NO_ENTRY;
+
+	return it->src->read_xattr(it->src, out);
+}
+
+sqfs_dir_iterator_t *tar_compat_iterator_create(const char *filename)
+{
+	sqfs_dir_iterator_t *base = NULL;
+	sqfs_id_table_t *idtbl = NULL;
+	sqfs_compressor_t *cmp = NULL;
+	sqfs_dir_reader_t *dr = NULL;
+	sqfs_data_reader_t *data = NULL;
+	sqfs_xattr_reader_t *xr = NULL;
+	sqfs_compressor_config_t cfg;
+	sqfs_file_t *file = NULL;
+	iterator_t *it = NULL;
+	int ret;
+
+	it = calloc(1, sizeof(*it));
+	if (it == NULL) {
+		perror("tar iterator");
+		return NULL;
+	}
+
+	/* open the file and read the super block */
+	ret = sqfs_file_open(&file, filename, SQFS_FILE_OPEN_READ_ONLY);
+	if (ret) {
+		sqfs_perror(filename, NULL, ret);
+		goto fail;
+	}
+
+	ret = sqfs_super_read(&it->super, file);
+	if (ret) {
+		sqfs_perror(filename, "reading super block", ret);
+		goto fail;
+	}
+
+	/* create a compressor */
+	sqfs_compressor_config_init(&cfg, it->super.compression_id,
+				    it->super.block_size,
+				    SQFS_COMP_FLAG_UNCOMPRESS);
+
+	ret = sqfs_compressor_create(&cfg, &cmp);
+
+#ifdef WITH_LZO
+	if (it->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 fail;
+	}
+
+	/* create a directory reader */
+	dr = sqfs_dir_reader_create(&it->super, cmp, file, 0);
+	if (dr == NULL) {
+		sqfs_perror(filename, "creating dir reader",
+			    SQFS_ERROR_ALLOC);
+		goto fail;
+	}
+
+	/* load ID table */
+	idtbl = sqfs_id_table_create(0);
+	if (idtbl == NULL) {
+		ret = SQFS_ERROR_ALLOC;
+	} else {
+		ret = sqfs_id_table_read(idtbl, file, &it->super, cmp);
+	}
+
+	if (ret) {
+		sqfs_perror(filename, "loading ID table", ret);
+		goto fail;
+	}
+
+	/* create data reader */
+	data = sqfs_data_reader_create(file, it->super.block_size, cmp, 0);
+	if (data == NULL) {
+		sqfs_perror(filename, "creating data reader",
+			    SQFS_ERROR_ALLOC);
+		goto fail;
+	}
+
+	ret = sqfs_data_reader_load_fragment_table(data, &it->super);
+	if (ret) {
+		sqfs_perror(filename, "loading fragment table", ret);
+		goto fail;
+	}
+
+	/* create xattr reader */
+	if (!no_xattr && !(it->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 fail;
+		}
+
+		ret = sqfs_xattr_reader_load(xr, &it->super, file, cmp);
+		if (ret) {
+			sqfs_perror(filename, "loading xattr table", ret);
+			goto fail;
+		}
+	}
+
+	/* get the root inode */
+	ret = sqfs_dir_reader_get_root_inode(dr, &it->root);
+	if (ret) {
+		sqfs_perror(filename, "reading root inode", ret);
+		goto fail;
+	}
+
+	/* create a recursive directory iterator from there */
+	ret = sqfs_dir_iterator_create(dr, idtbl, data, xr, it->root, &base);
+	if (ret) {
+		sqfs_perror(filename, "opening root directory", ret);
+		goto fail;
+	}
+
+	ret = sqfs_dir_iterator_create_recursive(&it->src, base);
+	base = sqfs_drop(base);
+	if (ret) {
+		sqfs_perror(filename, "creating directory scanner", ret);
+		goto fail;
+	}
+
+	/* get root attributes if we need them */
+	if (root_becomes == NULL) {
+		sqfs_free(it->root);
+		it->root = NULL;
+
+		it->state = STATE_ENTRY;
+	} else {
+		sqfs_u32 idx;
+
+		ret = sqfs_id_table_index_to_id(idtbl, it->root->base.uid_idx,
+						&it->root_uid);
+		if (ret == 0) {
+			ret = sqfs_id_table_index_to_id(idtbl,
+							it->root->base.gid_idx,
+							&it->root_gid);
+		}
+
+		if (ret == 0)
+			ret = sqfs_inode_get_xattr_index(it->root, &idx);
+
+		if (xr != NULL && ret == 0)
+			ret = sqfs_xattr_reader_read_all(xr, idx,
+							 &it->root_xattr);
+		if (ret) {
+			sqfs_perror(filename, "reading root inode attributes",
+				    ret);
+			goto fail;
+		}
+
+		it->state = STATE_INITIALIZED;
+	}
+
+	/* finish up initialization */
+	sqfs_object_init(it, destroy, NULL);
+	((sqfs_dir_iterator_t *)it)->next = next;
+	((sqfs_dir_iterator_t *)it)->read_link = read_link;
+	((sqfs_dir_iterator_t *)it)->open_file_ro = open_file_ro;
+	((sqfs_dir_iterator_t *)it)->read_xattr = read_xattr;
+out:
+	xr = sqfs_drop(xr);
+	dr = sqfs_drop(dr);
+	cmp = sqfs_drop(cmp);
+	file = sqfs_drop(file);
+	idtbl = sqfs_drop(idtbl);
+	data = sqfs_drop(data);
+	return (sqfs_dir_iterator_t *)it;
+fail:
+	sqfs_free(it->root);
+	sqfs_drop(it->src);
+	free(it);
+	it = NULL;
+	goto out;
+}
diff --git a/bin/sqfs2tar/src/sqfs2tar.c b/bin/sqfs2tar/src/sqfs2tar.c
index e21cd7a..786182c 100644
--- a/bin/sqfs2tar/src/sqfs2tar.c
+++ b/bin/sqfs2tar/src/sqfs2tar.c
@@ -6,113 +6,96 @@
  */
 #include "sqfs2tar.h"
 
-sqfs_xattr_reader_t *xr;
-sqfs_data_reader_t *data;
-sqfs_super_t super;
-sqfs_ostream_t *out_file = NULL;
+static sqfs_ostream_t *out_file = NULL;
 
-static sqfs_file_t *file;
-
-char *assemble_tar_path(char *name, bool is_dir)
+static int terminate_archive(void)
 {
-	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;
+	char buffer[1024];
 
-	if (root_becomes != NULL) {
-		len = strlen(root_becomes);
+	memset(buffer, '\0', sizeof(buffer));
 
-		memmove(name + len + 1, name, strlen(name) + 1);
-		memcpy(name, root_becomes, len);
-		name[len] = '/';
-	}
+	return out_file->append(out_file, buffer, sizeof(buffer));
+}
 
-	if (is_dir) {
-		len = strlen(name);
+static int write_file_data(sqfs_dir_iterator_t *it, const sqfs_dir_entry_t *ent)
+{
+	sqfs_istream_t *in;
+	int ret;
 
-		if (len == 0 || name[len - 1] != '/') {
-			name[len++] = '/';
-			name[len] = '\0';
-		}
-	}
+	ret = it->open_file_ro(it, &in);
+	if (ret)
+		return ret;
 
-	return name;
-}
+	do {
+		ret = sqfs_istream_splice(in, out_file,
+					  SQFS_DEFAULT_BLOCK_SIZE);
+	} while (ret > 0);
 
-static int terminate_archive(void)
-{
-	char buffer[1024];
+	in = sqfs_drop(in);
 
-	memset(buffer, '\0', sizeof(buffer));
+	if (ret == 0)
+		ret = padd_file(out_file, ent->size);
 
-	return out_file->append(out_file, buffer, sizeof(buffer));
+	return ret;
 }
 
-static sqfs_tree_node_t *tree_merge(sqfs_tree_node_t *lhs,
-				    sqfs_tree_node_t *rhs)
+static int write_entry(sqfs_dir_iterator_t *it, const sqfs_dir_entry_t *ent)
 {
-	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);
+	static unsigned int record_counter;
+	sqfs_xattr_t *xattr = NULL;
+	char *target = NULL;
+	struct stat sb;
+	int ret;
+
+	if (S_ISLNK(ent->mode) ||
+	    (ent->flags & SQFS_DIR_ENTRY_FLAG_HARD_LINK)) {
+		ret = it->read_link(it, &target);
+
+		if (ret != 0) {
+			sqfs_perror(ent->name, "reading link target", ret);
+			return ret;
 		}
+	}
 
-		*next_ptr = it;
-		next_ptr = &it->next;
+	ret = it->read_xattr(it, &xattr);
+	if (ret != 0) {
+		sqfs_perror(ent->name, "reading xattr data", ret);
+		sqfs_free(target);
+		return ret;
+	}
+
+	memset(&sb, 0, sizeof(sb));
+	sb.st_mode = ent->mode;
+	sb.st_uid = ent->uid;
+	sb.st_gid = ent->gid;
+	sb.st_mtime = ent->mtime;
+	sb.st_rdev = ent->rdev;
+	sb.st_size = ent->size;
+
+	if (ent->flags & SQFS_DIR_ENTRY_FLAG_HARD_LINK) {
+		ret = write_hard_link(out_file, &sb, ent->name, target,
+				      record_counter++);
+		if (ret)
+			sqfs_perror(ent->name, "writing tar hard link", ret);
+	} else {
+		ret = write_tar_header(out_file, &sb, ent->name, target,
+				       xattr, record_counter++);
+		if (ret)
+			sqfs_perror(ent->name, "writing tar header", ret);
 	}
 
-	it = (lhs->children != NULL ? lhs->children : rhs->children);
-	*next_ptr = it;
+	if (S_ISREG(ent->mode) && ret == 0)
+		ret = write_file_data(it, ent);
 
-	sqfs_dir_tree_destroy(rhs);
-	lhs->children = head;
-	return lhs;
+	sqfs_xattr_list_free(xattr);
+	sqfs_free(target);
+	return ret;
 }
 
 int main(int argc, char **argv)
 {
-	sqfs_tree_node_t *root = NULL, *subtree = NULL;
-	int flags, ret, status = EXIT_FAILURE;
-	sqfs_compressor_t *cmp = NULL;
-	sqfs_id_table_t *idtbl = NULL;
-	sqfs_dir_reader_t *dr = NULL;
-	sqfs_compressor_config_t cfg;
+	int ret, status = EXIT_FAILURE;
+	sqfs_dir_iterator_t *it = NULL;
 	size_t i;
 
 	process_args(argc, argv);
@@ -139,117 +122,59 @@ int main(int argc, char **argv)
 			goto out;
 	}
 
-	ret = sqfs_file_open(&file, filename, SQFS_FILE_OPEN_READ_ONLY);
-	if (ret) {
-		sqfs_perror(filename, "open", ret);
-		goto out;
-	}
-
-	ret = sqfs_super_read(&super, file);
-	if (ret) {
-		sqfs_perror(filename, "reading super block", ret);
-		goto out;
-	}
-
-	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);
+	it = tar_compat_iterator_create(filename);
+	if (it == NULL)
 		goto out;
-	}
 
-	idtbl = sqfs_id_table_create(0);
+	if (!no_links) {
+		sqfs_dir_iterator_t *hl;
 
-	if (idtbl == NULL) {
-		perror("creating ID table");
-		goto out;
-	}
+		ret = sqfs_hard_link_filter_create(&hl, it);
+		it = sqfs_drop(it);
 
-	ret = sqfs_id_table_read(idtbl, file, &super, cmp);
-	if (ret) {
-		sqfs_perror(filename, "loading ID table", ret);
-		goto out;
-	}
-
-	data = sqfs_data_reader_create(file, super.block_size, cmp, 0);
-	if (data == NULL) {
-		sqfs_perror(filename, "creating data reader",
-			    SQFS_ERROR_ALLOC);
-		goto out;
-	}
+		if (ret != 0) {
+			sqfs_perror(filename, "creating hard link filter", ret);
+			goto out;
+		}
 
-	ret = sqfs_data_reader_load_fragment_table(data, &super);
-	if (ret) {
-		sqfs_perror(filename, "loading fragment table", ret);
-		goto out;
+		it = hl;
 	}
 
-	dr = sqfs_dir_reader_create(&super, cmp, file, 0);
-	if (dr == NULL) {
-		sqfs_perror(filename, "creating dir reader",
-			    SQFS_ERROR_ALLOC);
-		goto out;
-	}
+	for (;;) {
+		sqfs_dir_entry_t *ent;
 
-	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);
+		ret = it->next(it, &ent);
+		if (ret > 0)
+			break;
+		if (ret < 0) {
+			sqfs_perror(filename, "reading directory entry", ret);
 			goto out;
 		}
 
-		ret = sqfs_xattr_reader_load(xr, &super, file, cmp);
-		if (ret) {
-			sqfs_perror(filename, "loading xattr table", ret);
-			goto out;
+		ret = write_entry(it, ent);
+		if (ret == SQFS_ERROR_UNSUPPORTED) {
+			fprintf(stderr, "WARNING: %s: unsupported file type\n",
+				ent->name);
+			if (dont_skip) {
+				fputs("Not allowed to skip files, aborting!\n",
+				      stderr);
+				sqfs_free(ent);
+				goto out;
+			}
+			fprintf(stderr, "Skipping %s\n", ent->name);
+			sqfs_free(ent);
+			continue;
 		}
-	}
 
-	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);
+			sqfs_perror(ent->name, NULL, ret);
+			sqfs_free(ent);
 			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);
-			}
-		}
+		sqfs_free(ent);
 	}
 
-	if (write_tree(root))
-		goto out;
-
 	if (terminate_archive())
 		goto out;
 
@@ -261,13 +186,7 @@ int main(int argc, char **argv)
 
 	status = EXIT_SUCCESS;
 out:
-	sqfs_dir_tree_destroy(root);
-	sqfs_drop(xr);
-	sqfs_drop(dr);
-	sqfs_drop(data);
-	sqfs_drop(idtbl);
-	sqfs_drop(cmp);
-	sqfs_drop(file);
+	sqfs_drop(it);
 	sqfs_drop(out_file);
 	for (i = 0; i < num_subdirs; ++i)
 		free(subdirs[i]);
diff --git a/bin/sqfs2tar/src/sqfs2tar.h b/bin/sqfs2tar/src/sqfs2tar.h
index bb07092..a1a5927 100644
--- a/bin/sqfs2tar/src/sqfs2tar.h
+++ b/bin/sqfs2tar/src/sqfs2tar.h
@@ -38,15 +38,7 @@ 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_ostream_t *out_file;
-
-char *assemble_tar_path(char *name, bool is_dir);
-
-/* write_tree.c */
-int write_tree(const sqfs_tree_node_t *n);
+/* iterator.c */
+sqfs_dir_iterator_t *tar_compat_iterator_create(const char *filename);
 
 #endif /* SQFS2TAR_H */
diff --git a/bin/sqfs2tar/src/write_tree.c b/bin/sqfs2tar/src/write_tree.c
deleted file mode 100644
index ed82173..0000000
--- a/bin/sqfs2tar/src/write_tree.c
+++ /dev/null
@@ -1,236 +0,0 @@
-/* SPDX-License-Identifier: GPL-3.0-or-later */
-/*
- * write_tree.c
- *
- * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
- */
-#include "sqfs2tar.h"
-
-static sqfs_hard_link_t *links = NULL;
-static unsigned int record_counter;
-
-static sqfs_hard_link_t *find_hard_link(const char *name, sqfs_u32 inum)
-{
-	sqfs_hard_link_t *lnk = NULL;
-
-	for (lnk = links; lnk != NULL; lnk = lnk->next) {
-		if (lnk->inode_number == inum) {
-			if (strcmp(name, lnk->target) == 0)
-				lnk = NULL;
-			break;
-		}
-	}
-
-	return lnk;
-}
-
-static void inode_stat(const sqfs_tree_node_t *node, struct stat *sb)
-{
-	memset(sb, 0, sizeof(*sb));
-
-	sb->st_mode = node->inode->base.mode;
-	sb->st_uid = node->uid;
-	sb->st_gid = node->gid;
-	sb->st_mtime = node->inode->base.mod_time;
-
-	switch (node->inode->base.type) {
-	case SQFS_INODE_BDEV:
-	case SQFS_INODE_CDEV:
-		sb->st_rdev = node->inode->data.dev.devno;
-		break;
-	case SQFS_INODE_EXT_BDEV:
-	case SQFS_INODE_EXT_CDEV:
-		sb->st_rdev = node->inode->data.dev_ext.devno;
-		break;
-	case SQFS_INODE_SLINK:
-		sb->st_size = node->inode->data.slink.target_size;
-		break;
-	case SQFS_INODE_EXT_SLINK:
-		sb->st_size = node->inode->data.slink_ext.target_size;
-		break;
-	case SQFS_INODE_FILE:
-		sb->st_size = node->inode->data.file.file_size;
-		break;
-	case SQFS_INODE_EXT_FILE:
-		sb->st_size = node->inode->data.file_ext.file_size;
-		break;
-	case SQFS_INODE_DIR:
-		sb->st_size = node->inode->data.dir.size;
-		break;
-	case SQFS_INODE_EXT_DIR:
-		sb->st_size = node->inode->data.dir_ext.size;
-		break;
-	default:
-		break;
-	}
-}
-
-static int write_tree_dfs(const sqfs_tree_node_t *n)
-{
-	sqfs_hard_link_t *lnk = NULL;
-	sqfs_xattr_t *xattr = 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;
-		}
-
-		ret = sqfs_tree_node_get_path(n, &name);
-		if (ret != 0) {
-			sqfs_perror(NULL, "resolving tree node path", ret);
-			return -1;
-		}
-
-		if (canonicalize_name(name))
-			goto out_skip;
-
-		name = assemble_tar_path(name, S_ISDIR(sb.st_mode));
-		if (name == NULL)
-			return -1;
-
-		lnk = find_hard_link(name, n->inode->base.inode_number);
-		if (lnk != NULL) {
-			ret = write_hard_link(out_file, &sb, name, lnk->target,
-					      record_counter++);
-			if (ret != 0)
-				sqfs_perror(name, "writing hard link", ret);
-			sqfs_free(name);
-			return ret;
-		}
-	}
-
-	if (!no_xattr && xr != NULL) {
-		sqfs_u32 index;
-		int ret;
-
-		sqfs_inode_get_xattr_index(n->inode, &index);
-
-		ret = sqfs_xattr_reader_read_all(xr, index, &xattr);
-		if (ret) {
-			sqfs_perror(name, "resolving xattr index", ret);
-			sqfs_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++);
-	sqfs_xattr_list_free(xattr);
-
-	if (ret == SQFS_ERROR_UNSUPPORTED) {
-		fprintf(stderr, "WARNING: %s: unsupported file type\n", name);
-		goto out_skip;
-	}
-
-	if (ret < 0) {
-		sqfs_perror(name, "writing tar header", ret);
-		sqfs_free(name);
-		return -1;
-	}
-
-	if (S_ISREG(sb.st_mode)) {
-		sqfs_istream_t *in;
-		int ret;
-
-		ret = sqfs_data_reader_create_stream(data, n->inode, name, &in);
-		if (ret) {
-			sqfs_perror(name, NULL, ret);
-			sqfs_free(name);
-			return -1;
-		}
-
-		do {
-			ret = sqfs_istream_splice(in, out_file,
-						  super.block_size);
-		} while (ret > 0);
-
-		sqfs_drop(in);
-
-		if (ret == 0)
-			ret = padd_file(out_file, sb.st_size);
-
-		if (ret) {
-			sqfs_perror(name, NULL, ret);
-			sqfs_free(name);
-			return -1;
-		}
-	}
-
-	sqfs_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;
-	}
-	sqfs_free(name);
-	return ret;
-}
-
-int write_tree(const sqfs_tree_node_t *n)
-{
-	sqfs_hard_link_t *lnk;
-	int status = -1;
-
-	if (!no_links) {
-		int ret = sqfs_tree_find_hard_links(n, &links);
-		if (ret) {
-			sqfs_perror(NULL, "detecting hard links in "
-				    "file system tree", ret);
-			return -1;
-		}
-
-		for (lnk = links; lnk != NULL; lnk = lnk->next) {
-			lnk->target = assemble_tar_path(lnk->target, false);
-
-			if (lnk->target == NULL)
-				goto out_links;
-		}
-	}
-
-	status = write_tree_dfs(n);
-out_links:
-	while (links != NULL) {
-		lnk = links;
-		links = links->next;
-		sqfs_free(lnk->target);
-		free(lnk);
-	}
-	return status;
-}