[PATCH v2 12/16] erofs-utils: add erofs image helper

[Jingbo Xu <jefflexu@linux.alibaba.com>]

Later we are going to introduce new feature of merging multiple erofs
images generated from tarfs mode.  Add helpers registering and cleaning
these images.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
 include/erofs/rebuild.h | 12 +++++++++++
 lib/rebuild.c           | 45 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/include/erofs/rebuild.h b/include/erofs/rebuild.h
index 92873c9..df7613a 100644
--- a/include/erofs/rebuild.h
+++ b/include/erofs/rebuild.h
@@ -9,6 +9,18 @@ extern "C"
 
 #include "internal.h"
 
+struct erofs_img {
+	struct list_head list;
+	char *path;
+	dev_t dev;
+	struct erofs_sb_info sbi;
+};
+
+extern unsigned int imgs_count;
+struct erofs_img *erofs_get_img(const char *path);
+int erofs_add_img(const char *path);
+void erofs_cleanup_imgs(void);
+
 struct erofs_dentry *erofs_rebuild_get_dentry(struct erofs_inode *pwd,
 		char *path, bool aufs, bool *whout, bool *opq);
 
diff --git a/lib/rebuild.c b/lib/rebuild.c
index 7aaa071..e2f6c1d 100644
--- a/lib/rebuild.c
+++ b/lib/rebuild.c
@@ -16,6 +16,9 @@
 #define AUFS_WH_DIROPQ		AUFS_WH_PFX AUFS_DIROPQ_NAME
 #endif
 
+unsigned int imgs_count;
+static LIST_HEAD(imgs_list);
+
 static struct erofs_dentry *erofs_rebuild_mkdir(struct erofs_inode *dir,
 						const char *s)
 {
@@ -115,3 +118,45 @@ struct erofs_dentry *erofs_rebuild_get_dentry(struct erofs_inode *pwd,
 	}
 	return d;
 }
+
+struct erofs_img *erofs_get_img(const char *path)
+{
+	struct erofs_img *img = malloc(sizeof(*img));
+
+	if (!img)
+		return ERR_PTR(-ENOMEM);
+
+	img->path = realpath(path, NULL);
+	if (!img->path) {
+		erofs_err("failed to parse image file (%s): %s",
+			  path, erofs_strerror(-errno));
+		free(img);
+		return ERR_PTR(-ENOENT);
+	}
+
+	img->dev = ++imgs_count;
+	return img;
+}
+
+int erofs_add_img(const char *path)
+{
+	struct erofs_img *img = erofs_get_img(path);
+
+	if (IS_ERR(img))
+		return PTR_ERR(img);
+
+	list_add_tail(&img->list, &imgs_list);
+	return 0;
+}
+
+void erofs_cleanup_imgs(void)
+{
+	struct erofs_img *img, *n;
+
+	list_for_each_entry_safe(img, n, &imgs_list, list) {
+		list_del(&img->list);
+		free(img->path);
+		free(img);
+	}
+	imgs_count = 0;
+}
-- 
2.19.1.6.gb485710b