btrfs: documented Attribute and AttributeIterator classes (no functional change)

Change-Id: I3bbd36132824df49339ceb98e811e36942714447

src/add-ons/kernel/file_systems/btrfs/Attribute.h

@@ -1,4 +1,5 @@
 /*
+ * Copyright 2019, Bharathi Ramana Joshi, [email protected].
  * Copyright 2017, Chế Vũ Gia Hy, [email protected].
  * Copyright 2010-2011, Jérôme Duval, [email protected].
  * Copyright 2004-2008, Axel Dörfler, [email protected].
@@ -20,27 +21,41 @@ struct attr_cookie {
 };
 
 
+/** Attributes in btrfs use the same on-disk format as directories, in the
+ * XATTR_ITEM of the inode. Each attribute appears as a "file" there.
+ *
+ * Additionally, this class provides access to the non-extended attributes
+ * through the Stat method. These are stored dorectly in the base inode of
+ * the file.
+ */
 class Attribute {
 public:
+			//! Constructs an Attribute object for the file inode
 								Attribute(Inode* inode);
 								Attribute(Inode* inode, attr_cookie* cookie);
 								~Attribute();
 
+			//! Tests if operations specified by openMode can be performed on file *name
 			status_t			CheckAccess(const char* name, int openMode);
 
 			status_t			Create(const char* name, type_code type,
 									int openMode, attr_cookie** _cookie);
+			//! Loads file attributes into cookie
 			status_t			Open(const char* name, int openMode,
 									attr_cookie** _cookie);
 
+			//! Get the stat from the attribute
 			status_t			Stat(struct stat& stat);
 
+			//! Loads extended attributes of file into buffer
 			status_t			Read(attr_cookie* cookie, off_t pos,
 									uint8* buffer, size_t* _length);
 private:
+			//! Searches through the filesystem tree for the entry named *name
 			status_t			_Lookup(const char* name, size_t nameLength,
 									btrfs_dir_entry** entries = NULL,
 									uint32* length = NULL);
+			//! Searches through the entry array for the entry named *name
 			status_t			_FindEntry(btrfs_dir_entry* entries,
 									size_t length, const char* name,
 									size_t nameLength,

src/add-ons/kernel/file_systems/btrfs/AttributeIterator.h

@@ -10,19 +10,29 @@
 #include "BTree.h"
 #include "Inode.h"
 
-
+//! Used to traverse through attributes of a given inode
 class AttributeIterator {
 public:
+			//! Constructs an AttributeIterator object for Inode object *inode
 								AttributeIterator(Inode* inode);
 								~AttributeIterator();
-
+			//! Check if fIterator pointer is valid 
 			status_t			InitCheck();
 
+			/*! Copy details of next Attribute into *name and *_nameLength
+			 * \param[out] name name of the current attribute
+			 * \param[out] _nameLength length of name
+			 * \return B_OK on success, B_ENTRY_NOT_FOUND otherwise
+			*/
 			status_t			GetNext(char* name, size_t* _nameLength);
+			//! Rewind the iterator to the first attribute of the node
 			status_t			Rewind();
 private:
+			//! Value of current offset from beginning of Attribute list
 			uint64				fOffset;
+			//! Pointer to Inode object corresponding to AttributeIterator
 			Inode* 				fInode;
+			//! Pointer to beginning of current Attribute
 			TreeIterator*		fIterator;
 };