Fast API for File read/Write

[madhusushmi]

I am looking for fastest API to read/write files. Can you please help?

[webJose]

For Windows there's only one: CreateFile(), ReadFile(), WriteFile(). For other OS' I have no idea.

[JLBorges]

If the file does not grow or shrink in size, memory mapping the file would give the fastest reads/writes.
http://www.freebsd.org/cgi/man.cgi?query=mmap&apropos=0&sektion=0&manpath=FreeBSD+9.0-RELEASE&arch=default&format=html
Windows: MapViewOfFile

If not, buffered asynchronous i/o (with a pool of buffers) would be worth considering.
http://www.freebsd.org/cgi/man.cgi?query=aio_write&apropos=0&sektion=0&manpath=FreeBSD+9.0-RELEASE&arch=default&format=html
Windows: WriteFileEx (on a file opened with FILE_FLAG_OVERLAPPED)