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syscall: implement nametomib for openbsd.

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Move the existing darwin/freebsd specific nametomib implementation
into the respective operating system dependent files.

Provide a nametomib implementation for openbsd, which operates on a
sysctl MIB that has been pre-generated from the various system headers
by mksysctl_openbsd.pl.

R=rsc
CC=golang-dev
https://golang.org/cl/4935044
This commit is contained in:
Joel Sing 2011-11-17 23:13:49 +11:00
parent a1dbfa6f09
commit 773a921ccb
8 changed files with 629 additions and 25 deletions
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25
src/pkg/syscall/syscall_bsd.go
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@ -546,31 +546,6 @@ func Kevent(kq int, changes, events []Kevent_t, timeout *Timespec) (n int, err e
//sys sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err error) = SYS___SYSCTL
// Translate "kern.hostname" to []_C_int{0,1,2,3}.
func nametomib(name string) (mib []_C_int, err error) {
const siz = unsafe.Sizeof(mib[0])
// NOTE(rsc): It seems strange to set the buffer to have
// size CTL_MAXNAME+2 but use only CTL_MAXNAME
// as the size. I don't know why the +2 is here, but the
// kernel uses +2 for its own implementation of this function.
// I am scared that if we don't include the +2 here, the kernel
// will silently write 2 words farther than we specify
// and we'll get memory corruption.
var buf [CTL_MAXNAME + 2]_C_int
n := uintptr(CTL_MAXNAME) * siz
p := (*byte)(unsafe.Pointer(&buf[0]))
bytes := StringByteSlice(name)
// Magic sysctl: "setting" 0.3 to a string name
// lets you read back the array of integers form.
if err = sysctl([]_C_int{0, 3}, p, &n, &bytes[0], uintptr(len(name))); err != nil {
return nil, err
}
return buf[0 : n/siz], nil
}
func Sysctl(name string) (value string, err error) {
// Translate name to mib number.
mib, err := nametomib(name)