File system operations.

Hi, hackers!

Do we have any standard set of functions to operate with files?

I mean link(), copy(), rename(), unlink(), ftruncate() and so on.
Mostly I worry about the first two since they have different
implementation on Windows.
I found a couple of functions in src/backend/storage/file/copydir.c,
some more in src/bin/pg_upgrade/file.c along with a set of defines
in src/bin/pg_upgrade/pg_upgrade.h. Obviously md.c and fd.c contain
some functions.
Do we have any policy of using them? There is a comment in fd.c

* For this scheme to work, most (if not all) routines throughout the
* server should use these interfaces instead of calling the C library
* routines (e.g., open(2) and fopen(3)) themselves. Otherwise, we
* may find ourselves short of real file descriptors anyway.

and even more in fd.h

* File {Close, Read, Write, Seek, Tell, Sync}
* {Path Name Open, Allocate, Free} File
*
* These are NOT JUST RENAMINGS OF THE UNIX ROUTINES.
* Use them for all file activity...

but I see that, for example, pg_open_tzfile() and get_controlfile(),
logfile_open()
call open()/fopen() directly. Same behavior you can find for any C
library function.
Am I missing something important or it is simply a legasy/overlooked code?

What do you think about moving stuff from pg_upgrade/file.c to storage/file/
to allow reuse of this code? I think it'll be really helpful for
developers of contrib modules
like backup managers.

--
Anastasia Lubennikova
Postgres Professional:http://www.postgrespro.com
The Russian Postgres Company