[Chicken-users] S_IFMT constants

[Alaric Snell-Pym]

Hello there,

The posix unit supplies a useful set of constants for file permission
bits. But, the file-stat procedure returns a mode bit that contains
some combination of those ORed together, *plus* some extra bits to
specify the file type.

In the NetBSD manpages for stat(2), it looks like this, for example:

     #define S_IFMT 0170000           /* type of file */
     #define        S_IFIFO  0010000  /* named pipe (fifo) */
     #define        S_IFCHR  0020000  /* character special */
     #define        S_IFDIR  0040000  /* directory */
     #define        S_IFBLK  0060000  /* block special */
     #define        S_IFREG  0100000  /* regular */
     #define        S_IFLNK  0120000  /* symbolic link */
     #define        S_IFSOCK 0140000  /* socket */
     #define        S_IFWHT  0160000  /* whiteout */
     #define S_ISUID 0004000  /* set user id on execution */
     #define S_ISGID 0002000  /* set group id on execution */
     #define S_ISVTX 0001000  /* save swapped text even after use */
     #define S_IRUSR 0000400  /* read permission, owner */
     #define S_IWUSR 0000200  /* write permission, owner */
     #define S_IXUSR 0000100  /* execute/search permission, owner */
     #define S_IRGRP 0000040  /* read permission, group */
     #define S_IWGRP 0000020  /* write permission, group */
     #define S_IXGRP 0000010  /* execute/search permission, group */
     #define S_IROTH 0000004  /* read permission, other */
     #define S_IWOTH 0000002  /* write permission, other */
     #define S_IXOTH 0000001  /* execute/search permission, other */

Chicken doesn't seem to have a way to portably get the values of
S_IFMT and friends, unless I'm missing something; there are procedures
like stat-socket?, but each does its own stat syscall, and I want to
do a single state on a file then branch on the file's type, while also
using other elements of the stat result (this is for my backup system,
Ugarit).

So I propose the following be added to posixunix.scm (and posixwin?):

(define-foreign-variable _s_ifmt int "S_IFMT")
(define stat/ifmt _s_ifmt)

(define-foreign-variable _s_ififo int "S_IFIFO")
(define stat/ififo _s_ififo)
(define-foreign-variable _s_ifchr int "S_IFCHR")
(define stat/ifchr _s_ifchr)
(define-foreign-variable _s_ifdir int "S_IFDIR")
(define stat/ifdir _s_ifdir)
(define-foreign-variable _s_ifblk int "S_IFBLK")
(define stat/ifblk _s_ifblk)
(define-foreign-variable _s_ifreg int "S_IFREG")
(define stat/ifreg _s_ifreg)
(define-foreign-variable _s_iflnk int "S_IFLNK")
(define stat/iflnk _s_iflnk)
(define-foreign-variable _s_ifsock int "S_IFSOCK")
(define stat/ifsock _s_ifsock)

(as S_IFWHT isn't portable, I'm skipping it)

ABS

--
Alaric Snell-Pym
Work: http://www.snell-systems.co.uk/
Play: http://www.snell-pym.org.uk/alaric/
Blog: http://www.snell-pym.org.uk/?author=4