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>

2 files changed, 73 insertions, 0 deletions

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));
+}