cleanup: unify all the code that reads squashfs images

This commit creates a new data structure called 'sqfs_reader_t' that
takes care of all the repetetive tasks like opening the file, reading
the super block, creating the compressor, deserializing an fstree and
creating a data reader.

This in turn makes it possible to remove all the duplicate code from
rdsquashfs and sqfs2tar.

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

5 files changed, 118 insertions, 108 deletions

diff --git a/include/highlevel.h b/include/highlevel.h
index e3afbd7..f8c5bfb 100644
--- a/include/highlevel.h
+++ b/include/highlevel.h
@@ -9,6 +9,7 @@
 
 #include "config.h"
 
+#include "data_reader.h"
 #include "squashfs.h"
 #include "compress.h"
 #include "id_table.h"
@@ -17,6 +18,14 @@
 #include <stdint.h>
 #include <stddef.h>
 
+typedef struct {
+	compressor_t *cmp;
+	data_reader_t *data;
+	sqfs_super_t super;
+	fstree_t fs;
+	int sqfsfd;
+} sqfs_reader_t;
+
 enum RDTREE_FLAGS {
 	RDTREE_NO_DEVICES = 0x01,
 	RDTREE_NO_SOCKETS = 0x02,
@@ -96,4 +105,14 @@ int write_export_table(int outfd, fstree_t *fs, sqfs_super_t *super,
 /* Print out fancy statistics for squashfs packing tools */
 void sqfs_print_statistics(fstree_t *fs, sqfs_super_t *super);
 
+/* Open a squashfs file, extract all the information we may need and
+   construct datastructures we need to access its contents.
+   Returns 0 on success. Prints error messages to stderr on failure.
+*/
+int sqfs_reader_open(sqfs_reader_t *rd, const char *filename,
+		     int rdtree_flags);
+
+/* Cleanup after a successfull sqfs_reader_open */
+void sqfs_reader_close(sqfs_reader_t *rd);
+
 #endif /* HIGHLEVEL_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index c3451f4..82c910c 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -39,6 +39,7 @@ libsquashfs_a_SOURCES += include/data_writer.h include/xattr_reader.h
 libsquashfs_a_SOURCES += include/data_reader.h lib/sqfs/data_reader.c
 libsquashfs_a_SOURCES += lib/sqfs/write_export_table.c
 libsquashfs_a_SOURCES += lib/sqfs/read_table.c lib/sqfs/statistics.c
+libsquashfs_a_SOURCES += lib/sqfs/sqfs_reader.c
 
 libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_data.c
 libutil_a_SOURCES += lib/util/read_data.c include/util.h
diff --git a/lib/sqfs/sqfs_reader.c b/lib/sqfs/sqfs_reader.c
new file mode 100644
index 0000000..85cf97a
--- /dev/null
+++ b/lib/sqfs/sqfs_reader.c
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * sqfs_reader.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "highlevel.h"
+
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+int sqfs_reader_open(sqfs_reader_t *rd, const char *filename, int rdtree_flags)
+{
+	memset(rd, 0, sizeof(*rd));
+
+	rd->sqfsfd = open(filename, O_RDONLY);
+	if (rd->sqfsfd < 0) {
+		perror(filename);
+		return -1;
+	}
+
+	if (sqfs_super_read(&rd->super, rd->sqfsfd))
+		goto fail_fd;
+
+	if (!compressor_exists(rd->super.compression_id)) {
+		fprintf(stderr, "%s: unknown compressor used.\n", filename);
+		goto fail_fd;
+	}
+
+	rd->cmp = compressor_create(rd->super.compression_id, false,
+				    rd->super.block_size, NULL);
+	if (rd->cmp == NULL)
+		goto fail_fd;
+
+	if (rd->super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
+		if (rd->cmp->read_options(rd->cmp, rd->sqfsfd))
+			goto fail_cmp;
+	}
+
+	if (deserialize_fstree(&rd->fs, &rd->super, rd->cmp, rd->sqfsfd,
+			       rdtree_flags)) {
+		goto fail_cmp;
+	}
+
+	fstree_gen_file_list(&rd->fs);
+
+	rd->data = data_reader_create(rd->sqfsfd, &rd->super, rd->cmp);
+	if (rd->data == NULL)
+		goto fail_fs;
+
+	return 0;
+fail_fs:
+	fstree_cleanup(&rd->fs);
+fail_cmp:
+	rd->cmp->destroy(rd->cmp);
+fail_fd:
+	close(rd->sqfsfd);
+	memset(rd, 0, sizeof(*rd));
+	return -1;
+}
+
+void sqfs_reader_close(sqfs_reader_t *rd)
+{
+	data_reader_destroy(rd->data);
+	fstree_cleanup(&rd->fs);
+	rd->cmp->destroy(rd->cmp);
+	close(rd->sqfsfd);
+	memset(rd, 0, sizeof(*rd));
+}
diff --git a/tar/sqfs2tar.c b/tar/sqfs2tar.c
index a49efda..59e9703 100644
--- a/tar/sqfs2tar.c
+++ b/tar/sqfs2tar.c
@@ -302,89 +302,51 @@ skip_hdr:
 
 int main(int argc, char **argv)
 {
-	int sqfsfd, rdtree_flags = 0;
-	data_reader_t *data = NULL;
-	int status = EXIT_FAILURE;
-	sqfs_super_t super;
-	compressor_t *cmp;
+	int rdtree_flags = 0, status = EXIT_FAILURE;
+	sqfs_reader_t sqfs;
 	tree_node_t *root;
-	fstree_t fs;
 	size_t i;
 
 	process_args(argc, argv);
 
-	sqfsfd = open(filename, O_RDONLY);
-	if (sqfsfd < 0) {
-		perror(filename);
-		return EXIT_FAILURE;
-	}
-
-	if (sqfs_super_read(&super, sqfsfd))
-		goto out_fd;
-
-	if (!compressor_exists(super.compression_id)) {
-		fputs("Image uses a compressor that has not been built in\n",
-		      stderr);
-		goto out_fd;
-	}
-
-	cmp = compressor_create(super.compression_id, false,
-				super.block_size, NULL);
-	if (cmp == NULL)
-		goto out_fd;
-
-	if (super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
-		if (cmp->read_options(cmp, sqfsfd))
-			goto out_cmp;
-	}
-
 	if (!no_xattr)
 		rdtree_flags |= RDTREE_READ_XATTR;
 
-	if (deserialize_fstree(&fs, &super, cmp, sqfsfd, rdtree_flags))
-		goto out_cmp;
-
-	data = data_reader_create(sqfsfd, &super, cmp);
-	if (data == NULL)
-		goto out_fs;
+	if (sqfs_reader_open(&sqfs, filename, rdtree_flags))
+		goto out_dirs;
 
 	for (i = 0; i < num_subdirs; ++i) {
-		root = fstree_node_from_path(&fs, subdirs[i]);
+		root = fstree_node_from_path(&sqfs.fs, subdirs[i]);
 		if (root == NULL) {
 			perror(subdirs[i]);
-			goto out_data;
+			goto out;
 		}
 
 		if (!S_ISDIR(root->mode)) {
 			fprintf(stderr, "%s is not a directory\n", subdirs[i]);
-			goto out_data;
+			goto out;
 		}
 
 		current_subdir = subdirs[i];
 
-		if (write_tree_dfs(&fs, root, data))
-			goto out_data;
+		if (write_tree_dfs(&sqfs.fs, root, sqfs.data))
+			goto out;
 	}
 
 	current_subdir = NULL;
 
 	if (num_subdirs == 0) {
-		if (write_tree_dfs(&fs, fs.root, data))
-			goto out_data;
+		if (write_tree_dfs(&sqfs.fs, sqfs.fs.root, sqfs.data))
+			goto out;
 	}
 
 	if (terminate_archive())
-		goto out_data;
+		goto out;
 
 	status = EXIT_SUCCESS;
-out_data:
-	data_reader_destroy(data);
-out_fs:
-	fstree_cleanup(&fs);
-out_cmp:
-	cmp->destroy(cmp);
-out_fd:
-	close(sqfsfd);
+out:
+	sqfs_reader_close(&sqfs);
+out_dirs:
 	for (i = 0; i < num_subdirs; ++i)
 		free(subdirs[i]);
 	free(subdirs);
diff --git a/unpack/rdsquashfs.c b/unpack/rdsquashfs.c
index dc43fcd..4fb3a78 100644
--- a/unpack/rdsquashfs.c
+++ b/unpack/rdsquashfs.c
@@ -24,54 +24,23 @@ static void dump_xattrs(fstree_t *fs, tree_xattr_t *xattr)
 int main(int argc, char **argv)
 {
 	int status = EXIT_FAILURE;
-	data_reader_t *data = NULL;
-	sqfs_super_t super;
-	compressor_t *cmp;
+	sqfs_reader_t sqfs;
 	tree_node_t *n;
 	options_t opt;
-	fstree_t fs;
-	int sqfsfd;
 
 	process_command_line(&opt, argc, argv);
 
-	sqfsfd = open(opt.image_name, O_RDONLY);
-	if (sqfsfd < 0) {
-		perror(opt.image_name);
+	if (sqfs_reader_open(&sqfs, opt.image_name, opt.rdtree_flags))
 		goto out_cmd;
-	}
-
-	if (sqfs_super_read(&super, sqfsfd))
-		goto out_fd;
-
-	if (!compressor_exists(super.compression_id)) {
-		fputs("Image uses a compressor that has not been built in\n",
-		      stderr);
-		goto out_fd;
-	}
-
-	cmp = compressor_create(super.compression_id, false,
-				super.block_size, NULL);
-	if (cmp == NULL)
-		goto out_fd;
-
-	if (super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
-		if (cmp->read_options(cmp, sqfsfd))
-			goto out_cmp;
-	}
-
-	if (deserialize_fstree(&fs, &super, cmp, sqfsfd, opt.rdtree_flags))
-		goto out_cmp;
-
-	fstree_gen_file_list(&fs);
 
 	if (opt.cmdpath != NULL) {
-		n = fstree_node_from_path(&fs, opt.cmdpath);
+		n = fstree_node_from_path(&sqfs.fs, opt.cmdpath);
 		if (n == NULL) {
 			perror(opt.cmdpath);
 			goto out_fs;
 		}
 	} else {
-		n = fs.root;
+		n = sqfs.fs.root;
 	}
 
 	switch (opt.op) {
@@ -85,11 +54,7 @@ int main(int argc, char **argv)
 			goto out_fs;
 		}
 
-		data = data_reader_create(sqfsfd, &super, cmp);
-		if (data == NULL)
-			goto out_fs;
-
-		if (data_reader_dump_file(data, n->data.file,
+		if (data_reader_dump_file(sqfs.data, n->data.file,
 					  STDOUT_FILENO, false))
 			goto out_fs;
 		break;
@@ -105,38 +70,29 @@ int main(int argc, char **argv)
 		if (restore_fstree(n, opt.flags))
 			goto out_fs;
 
-		data = data_reader_create(sqfsfd, &super, cmp);
-		if (data == NULL)
-			goto out_fs;
-
-		if (fill_unpacked_files(&fs, data, opt.flags, opt.num_jobs))
+		if (fill_unpacked_files(&sqfs.fs, sqfs.data,
+					opt.flags, opt.num_jobs))
 			goto out_fs;
 
-		if (update_tree_attribs(&fs, n, opt.flags))
+		if (update_tree_attribs(&sqfs.fs, n, opt.flags))
 			goto out_fs;
 
 		if (opt.unpack_root != NULL && popd() != 0)
 			goto out_fs;
 		break;
 	case OP_DESCRIBE:
-		if (describe_tree(fs.root, opt.unpack_root))
+		if (describe_tree(sqfs.fs.root, opt.unpack_root))
 			goto out_fs;
 		break;
 	case OP_RDATTR:
 		if (n->xattr != NULL)
-			dump_xattrs(&fs, n->xattr);
+			dump_xattrs(&sqfs.fs, n->xattr);
 		break;
 	}
 
 	status = EXIT_SUCCESS;
 out_fs:
-	if (data != NULL)
-		data_reader_destroy(data);
-	fstree_cleanup(&fs);
-out_cmp:
-	cmp->destroy(cmp);
-out_fd:
-	close(sqfsfd);
+	sqfs_reader_close(&sqfs);
 out_cmd:
 	free(opt.cmdpath);
 	return status;