package hackers_git

import (
	"syscall"
	"unsafe"
)

//#define _XOPEN_SOURCE /* for getgrnam_r(3) in grp.h */
//#include <stdlib.h>   /* for free(3) */
//#include <unistd.h>   /* for sysconf(3) */
//#include <grp.h>      /* for getgrnam_r(3) */
import "C"

func name2gid(name string) (gid int32) {
	nameC := C.CString(name)
	defer C.free(unsafe.Pointer(nameC))

	gid = -1
	buflen := C.sysconf(C._SC_GETGR_R_SIZE_MAX)
	if buflen < 1 {
		buflen = 1024
	}
	buf := make([]byte, buflen)
	var grp C.struct_group
	var ret *C.struct_group
	for {
		success, errno := C.getgrnam_r(nameC, &grp, (*C.char)(unsafe.Pointer(&buf[0])), C.size_t(buflen), &ret)
		if success >= 0 {
			break
		}
		if errno == syscall.ERANGE {
			buflen += 256
			buf = make([]byte, buflen)
		} else {
			return
		}
	}
	if ret != nil {
		gid = int32(ret.gr_gid)
	}
	return
}