littlefs: Add lfs_file_getattr and lfs_file_setattr

lfs.c

@@ -6235,6 +6235,41 @@ lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file) {
     return res;
 }
 
+lfs_ssize_t lfs_file_getattr(lfs_t *lfs, lfs_file_t *file,
+        uint8_t type, void *buffer, lfs_size_t size)
+{
+    int err = LFS_LOCK(lfs->cfg);
+    if (err) {
+        return err;
+    }
+    LFS_TRACE("lfs_file_setattr(%p, %p)", (void*)lfs, (void*)file);
+    LFS_TRACE("lfs_file_setattr(%"PRIu8", %p, %"PRIu32")",
+            type, buffer, size);
+    LFS_ASSERT(lfs_mlist_isopen(lfs->mlist, (struct lfs_mlist*)file));
+
+    return lfs_dir_get(lfs, &file->m, LFS_MKTAG(0x7ff, 0x3ff, 0),
+            LFS_MKTAG(LFS_TYPE_USERATTR + type,
+                file->id, lfs_min(size, lfs->attr_max)), buffer);
+}
+
+#ifndef LFS_READONLY
+int lfs_file_setattr(lfs_t *lfs, lfs_file_t *file,
+        uint8_t type, const void *buffer, lfs_size_t size)
+{
+    int err = LFS_LOCK(lfs->cfg);
+    if (err) {
+        return err;
+    }
+    LFS_TRACE("lfs_file_getattr(%p, %p)", (void*)lfs, (void*)file);
+    LFS_TRACE("lfs_file_getattr(%"PRIu8", %p, %"PRIu32")",
+            type, buffer, size);
+    LFS_ASSERT(lfs_mlist_isopen(lfs->mlist, (struct lfs_mlist*)file));
+
+    return lfs_dir_commit(lfs, &file->m, LFS_MKATTRS(
+            {LFS_MKTAG(LFS_TYPE_USERATTR + type, file->id, size), buffer}));
+}
+#endif
+
 #ifndef LFS_READONLY
 int lfs_mkdir(lfs_t *lfs, const char *path) {
     int err = LFS_LOCK(lfs->cfg);

lfs.h

@@ -657,6 +657,33 @@ int lfs_file_rewind(lfs_t *lfs, lfs_file_t *file);
 lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file);
 
 
+// Get a custom attribute of file
+//
+// Custom attributes are uniquely identified by an 8-bit type and limited
+// to LFS_ATTR_MAX bytes. When read, if the stored attribute is smaller than
+// the buffer, it will be padded with zeros. If the stored attribute is larger,
+// then it will be silently truncated. If no attribute is found, the error
+// LFS_ERR_NOATTR is returned and the buffer is filled with zeros.
+//
+// Returns the size of the attribute, or a negative error code on failure.
+// Note, the returned size is the size of the attribute on disk, irrespective
+// of the size of the buffer. This can be used to dynamically allocate a buffer
+// or check for existance.
+lfs_ssize_t lfs_file_getattr(lfs_t *lfs, lfs_file_t *file,
+        uint8_t type, void *buffer, lfs_size_t size);
+
+// Set custom attributes of file
+//
+// Custom attributes are uniquely identified by an 8-bit type and limited
+// to LFS_ATTR_MAX bytes. If an attribute is not found, it will be
+// implicitly created.
+//
+// Returns a negative error code on failure.
+#ifndef LFS_READONLY
+int lfs_file_setattr(lfs_t *lfs, lfs_file_t *file,
+        uint8_t type, const void *buffer, lfs_size_t size);
+#endif
+
 /// Directory operations ///
 
 #ifndef LFS_READONLY