以下仿真C++的set_new_handler()。可以通过它指定自己的 out-of-memory handler

The start of the backup area:

根据区块大小，决定使用第n号free-list。n从0算起

The start of the main get area: FIXME: wrong for write-mode filebuf?

将bytes上调至8的倍数

Number of nonmatching characters

root is treated as a cached version of this, and is used to detect changes to the underlying rope. Root is included in the reference count. This is ne

As above, but assumes path cache is valid for previous posn.

s should really be an arbitrary input iterator. Adds a trailing NULL for basic char types.

n must be > 0 */

Allocate a buffer if needed; use _shortbuf if appropriate.