// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build aix
// +build ppc64

// Functions to access/create device major and minor numbers matching the
// encoding used by the Linux kernel and glibc.
//
// The information below is extracted and adapted from bits/sysmacros.h in the
// glibc sources:
//
// dev_t in glibc is 64-bit, with 32-bit major and minor numbers. glibc's
// default encoding is MMMM Mmmm mmmM MMmm, where M is a hex digit of the major
// number and m is a hex digit of the minor number. This is backward compatible
// with legacy systems where dev_t is 16 bits wide, encoded as MMmm. It is also
// backward compatible with the Linux kernel, which for some architectures uses
// 32-bit dev_t, encoded as mmmM MMmm.

package unix

// Major returns the major component of a Linux device number.
func Major(dev uint64) uint32 {
	return uint32((dev & 0x3fffffff00000000) >> 32)
}

// Minor returns the minor component of a Linux device number.
func Minor(dev uint64) uint32 {
	return uint32((dev & 0x00000000ffffffff) >> 0)
}

// Mkdev returns a Linux device number generated from the given major and minor
// components.
func Mkdev(major, minor uint32) uint64 {
	var DEVNO64 uint64
	DEVNO64 = 0x8000000000000000
	return ((uint64(major) << 32) | (uint64(minor) & 0x00000000FFFFFFFF) | DEVNO64)
}
