mirror of
https://github.com/mjl-/mox.git
synced 2024-12-27 08:53:48 +03:00
42 lines
1.5 KiB
Go
42 lines
1.5 KiB
Go
// Copyright 2017 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.
|
|
|
|
// 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 {
|
|
major := uint32((dev & 0x00000000000fff00) >> 8)
|
|
major |= uint32((dev & 0xfffff00000000000) >> 32)
|
|
return major
|
|
}
|
|
|
|
// Minor returns the minor component of a Linux device number.
|
|
func Minor(dev uint64) uint32 {
|
|
minor := uint32((dev & 0x00000000000000ff) >> 0)
|
|
minor |= uint32((dev & 0x00000ffffff00000) >> 12)
|
|
return minor
|
|
}
|
|
|
|
// Mkdev returns a Linux device number generated from the given major and minor
|
|
// components.
|
|
func Mkdev(major, minor uint32) uint64 {
|
|
dev := (uint64(major) & 0x00000fff) << 8
|
|
dev |= (uint64(major) & 0xfffff000) << 32
|
|
dev |= (uint64(minor) & 0x000000ff) << 0
|
|
dev |= (uint64(minor) & 0xffffff00) << 12
|
|
return dev
|
|
}
|