Added signatures for the backing system.

src/backing.h

@@ -4,3 +4,36 @@
 #include <stdint.h>
 
 #define BACKING_POOL "/var/lib/sandbox/backings"
+
+/// @brief Checks whether the backing pool exists and is a directory.
+/// @return True if the backing pool exists and is a directory, false otherwise.
+bool check_backing_pool(void);
+
+/// @brief Checks whether the backing disk id is valid.
+/// @param backing_id The backing disk id to check.
+/// @return True if the backing disk id is valid, false otherwise.
+bool is_backing_id_valid(const char* backing_id);
+
+/// @brief Checks whether the backing disk exists.
+/// @param backing_id The backing disk id to check.
+/// @return True if the backing disk exists, false otherwise.
+bool backing_exists(const char* backing_id);
+
+/// @brief Adds a backing disk to the backing pool.
+/// @param backing_id The backing disk id to add.
+/// @param entry_id The entry from which the backing disk should be added.
+/// @return True if the backing disk was added, false otherwise.
+bool add_backing(const char* backing_id, const char* entry_id);
+
+/// @brief Removes a backing disk from the backing pool, as well as any backing disks that depend on it.
+/// @param backing_id The backing disk id to remove.
+/// @return True if the backing disk was removed, false otherwise.
+bool remove_backing(const char* backing_id);
+
+/// @brief Lists all backing disks in the backing pool.
+/// @return An array of backing disk ids or NULL if an error occurred. The result must be freed with free(), as well as each individual backing disk id.
+char** list_backings(void);
+
+/// @brief Clears all backing disks from the backing pool.
+/// @return True if all backing disks were removed, false otherwise.
+bool clear_backings(void);