}
/*
+ * XFS btree block layout and addressing:
+ *
+ * There are two types of blocks in the btree: leaf and non-leaf blocks.
+ *
+ * The leaf record start with a header then followed by records containing
+ * the values. A non-leaf block also starts with the same header, and
+ * then first contains lookup keys followed by an equal number of pointers
+ * to the btree blocks at the previous level.
+ *
+ * +--------+-------+-------+-------+-------+-------+-------+
+ * Leaf: | header | rec 1 | rec 2 | rec 3 | rec 4 | rec 5 | rec N |
+ * +--------+-------+-------+-------+-------+-------+-------+
+ *
+ * +--------+-------+-------+-------+-------+-------+-------+
+ * Non-Leaf: | header | key 1 | key 2 | key N | ptr 1 | ptr 2 | ptr N |
+ * +--------+-------+-------+-------+-------+-------+-------+
+ *
+ * The header is called struct xfs_btree_block for reasons better left unknown
+ * and comes in different versions for short (32bit) and long (64bit) block
+ * pointers. The record and key structures are defined by the btree instances
+ * and opaque to the btree core. The block pointers are simple disk endian
+ * integers, available in a short (32bit) and long (64bit) variant.
+ *
+ * The helpers below calculate the offset of a given record, key or pointer
+ * into a btree block (xfs_btree_*_offset) or return a pointer to the given
+ * record, key or pointer (xfs_btree_*_addr). Note that all addressing
+ * inside the btree block is done using indices starting at one, not zero!
+ */
+
+/*
+ * Return size of the btree block header for this btree instance.
+ */
+static inline size_t xfs_btree_block_len(struct xfs_btree_cur *cur)
+{
+ return (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?
+ sizeof(struct xfs_btree_lblock) :
+ sizeof(struct xfs_btree_sblock);
+}
+
+/*
+ * Return size of btree block pointers for this btree instance.
+ */
+static inline size_t xfs_btree_ptr_len(struct xfs_btree_cur *cur)
+{
+ return (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?
+ sizeof(__be64) : sizeof(__be32);
+}
+
+/*
+ * Calculate offset of the n-th record in a btree block.
+ */
+STATIC size_t
+xfs_btree_rec_offset(
+ struct xfs_btree_cur *cur,
+ int n)
+{
+ return xfs_btree_block_len(cur) +
+ (n - 1) * cur->bc_ops->rec_len;
+}
+
+/*
+ * Calculate offset of the n-th key in a btree block.
+ */
+STATIC size_t
+xfs_btree_key_offset(
+ struct xfs_btree_cur *cur,
+ int n)
+{
+ return xfs_btree_block_len(cur) +
+ (n - 1) * cur->bc_ops->key_len;
+}
+
+/*
+ * Calculate offset of the n-th block pointer in a btree block.
+ */
+STATIC size_t
+xfs_btree_ptr_offset(
+ struct xfs_btree_cur *cur,
+ int n,
+ int level)
+{
+ return xfs_btree_block_len(cur) +
+ cur->bc_ops->get_maxrecs(cur, level) * cur->bc_ops->key_len +
+ (n - 1) * xfs_btree_ptr_len(cur);
+}
+
+/*
+ * Return a pointer to the n-th record in the btree block.
+ */
+STATIC union xfs_btree_rec *
+xfs_btree_rec_addr(
+ struct xfs_btree_cur *cur,
+ int n,
+ struct xfs_btree_block *block)
+{
+ return (union xfs_btree_rec *)
+ ((char *)block + xfs_btree_rec_offset(cur, n));
+}
+
+/*
+ * Return a pointer to the n-th key in the btree block.
+ */
+STATIC union xfs_btree_key *
+xfs_btree_key_addr(
+ struct xfs_btree_cur *cur,
+ int n,
+ struct xfs_btree_block *block)
+{
+ return (union xfs_btree_key *)
+ ((char *)block + xfs_btree_key_offset(cur, n));
+}
+
+/*
+ * Return a pointer to the n-th block pointer in the btree block.
+ */
+STATIC union xfs_btree_ptr *
+xfs_btree_ptr_addr(
+ struct xfs_btree_cur *cur,
+ int n,
+ struct xfs_btree_block *block)
+{
+ int level = xfs_btree_get_level(block);
+
+ ASSERT(block->bb_level != 0);
+
+ return (union xfs_btree_ptr *)
+ ((char *)block + xfs_btree_ptr_offset(cur, n, level));
+}
+
+/*
* Get a the root block which is stored in the inode.
*
* For now this btree implementation assumes the btree root is always
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