x/sys/unix: no major, minor, and mkdev functions

[gopherbot]

by tim.thelion:

Hello, I am in need of the Major, Minor, and Mkdev functions from the linux kernel:
https://github.com/torvalds/linux/blob/master/include/linux/kdev_t.h#L9 for converting a
device number produced by "stat.Sys().(*syscall.Stat_t)" to it's major and
minor components, and vice versa.  As you can see, simply imitating the kernel sources
won't work: http://play.golang.org/p/zvRqa2eEjN


Thank you for your time,

Timothy Hobbs

[ianlancetaylor]

Comment 1:

Labels changed: added repo-main, release-go1.4.

[gopherbot]

Comment 2 by tim.thelion:

Hopefully the bit-fiddling is all right here:
https://github.com/dotcloud/docker/pull/4191/files#diff-6ce9e79ddb91a3f06352abe1f2c72ecbR468
func Major(devNumber int) int64{
    return int64((devNumber >> 8) & 0xfff)
}
func Minor(devNumber int) int64{
    return int64((devNumber & 0xff) | ((devNumber >> 12) & 0xfff00))
}
func Mkdev(majorNumber int64,minorNumber int64) int{
    return int((majorNumber << 8) | (minorNumber & 0xff) | ((minorNumber & 0xfff00) << 12))
}
Not so sure about the last one, as I wrote it myself and I don't really understand the
format of the numbers and I am not an expert at bit fiddling.

[rsc]

Comment 3:

Labels changed: added repo-sys, release-none, removed repo-main, release-go1.4.

Status changed to Accepted.