如何可移植地扩展使用mmap（）访问的文件

We're experimenting with changing SQLite, an embedded database system, to use mmap() instead of the usual read() and write() calls to access the database file on disk. Using a single large mapping for the entire file. Assume that the file is small enough that we have no trouble finding space for this in virtual memory.We're experimenting with changing SQLite, an em