1// Copyright 2009 The Go Authors. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos
 6
 7// Package unix contains an interface to the low-level operating system
 8// primitives. OS details vary depending on the underlying system, and
 9// by default, godoc will display OS-specific documentation for the current
10// system. If you want godoc to display OS documentation for another
11// system, set $GOOS and $GOARCH to the desired system. For example, if
12// you want to view documentation for freebsd/arm on linux/amd64, set $GOOS
13// to freebsd and $GOARCH to arm.
14//
15// The primary use of this package is inside other packages that provide a more
16// portable interface to the system, such as "os", "time" and "net".  Use
17// those packages rather than this one if you can.
18//
19// For details of the functions and data types in this package consult
20// the manuals for the appropriate operating system.
21//
22// These calls return err == nil to indicate success; otherwise
23// err represents an operating system error describing the failure and
24// holds a value of type syscall.Errno.
25package unix // import "golang.org/x/sys/unix"
26
27import (
28	"bytes"
29	"strings"
30	"unsafe"
31)
32
33// ByteSliceFromString returns a NUL-terminated slice of bytes
34// containing the text of s. If s contains a NUL byte at any
35// location, it returns (nil, EINVAL).
36func ByteSliceFromString(s string) ([]byte, error) {
37	if strings.IndexByte(s, 0) != -1 {
38		return nil, EINVAL
39	}
40	a := make([]byte, len(s)+1)
41	copy(a, s)
42	return a, nil
43}
44
45// BytePtrFromString returns a pointer to a NUL-terminated array of
46// bytes containing the text of s. If s contains a NUL byte at any
47// location, it returns (nil, EINVAL).
48func BytePtrFromString(s string) (*byte, error) {
49	a, err := ByteSliceFromString(s)
50	if err != nil {
51		return nil, err
52	}
53	return &a[0], nil
54}
55
56// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any
57// bytes after the NUL removed.
58func ByteSliceToString(s []byte) string {
59	if i := bytes.IndexByte(s, 0); i != -1 {
60		s = s[:i]
61	}
62	return string(s)
63}
64
65// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.
66// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated
67// at a zero byte; if the zero byte is not present, the program may crash.
68func BytePtrToString(p *byte) string {
69	if p == nil {
70		return ""
71	}
72	if *p == 0 {
73		return ""
74	}
75
76	// Find NUL terminator.
77	n := 0
78	for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {
79		ptr = unsafe.Pointer(uintptr(ptr) + 1)
80	}
81
82	return string(unsafe.Slice(p, n))
83}
84
85// Single-word zero for use when we need a valid pointer to 0 bytes.
86var _zero uintptr