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// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos
 7
 8// Package unix contains an interface to the low-level operating system
 9// primitives. OS details vary depending on the underlying system, and
10// by default, godoc will display OS-specific documentation for the current
11// system. If you want godoc to display OS documentation for another
12// system, set $GOOS and $GOARCH to the desired system. For example, if
13// you want to view documentation for freebsd/arm on linux/amd64, set $GOOS
14// to freebsd and $GOARCH to arm.
15//
16// The primary use of this package is inside other packages that provide a more
17// portable interface to the system, such as "os", "time" and "net".  Use
18// those packages rather than this one if you can.
19//
20// For details of the functions and data types in this package consult
21// the manuals for the appropriate operating system.
22//
23// These calls return err == nil to indicate success; otherwise
24// err represents an operating system error describing the failure and
25// holds a value of type syscall.Errno.
26package unix // import "golang.org/x/sys/unix"
27
28import (
29	"bytes"
30	"strings"
31	"unsafe"
32)
33
34// ByteSliceFromString returns a NUL-terminated slice of bytes
35// containing the text of s. If s contains a NUL byte at any
36// location, it returns (nil, EINVAL).
37func ByteSliceFromString(s string) ([]byte, error) {
38	if strings.IndexByte(s, 0) != -1 {
39		return nil, EINVAL
40	}
41	a := make([]byte, len(s)+1)
42	copy(a, s)
43	return a, nil
44}
45
46// BytePtrFromString returns a pointer to a NUL-terminated array of
47// bytes containing the text of s. If s contains a NUL byte at any
48// location, it returns (nil, EINVAL).
49func BytePtrFromString(s string) (*byte, error) {
50	a, err := ByteSliceFromString(s)
51	if err != nil {
52		return nil, err
53	}
54	return &a[0], nil
55}
56
57// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any
58// bytes after the NUL removed.
59func ByteSliceToString(s []byte) string {
60	if i := bytes.IndexByte(s, 0); i != -1 {
61		s = s[:i]
62	}
63	return string(s)
64}
65
66// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.
67// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated
68// at a zero byte; if the zero byte is not present, the program may crash.
69func BytePtrToString(p *byte) string {
70	if p == nil {
71		return ""
72	}
73	if *p == 0 {
74		return ""
75	}
76
77	// Find NUL terminator.
78	n := 0
79	for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {
80		ptr = unsafe.Pointer(uintptr(ptr) + 1)
81	}
82
83	return string(unsafe.Slice(p, n))
84}
85
86// Single-word zero for use when we need a valid pointer to 0 bytes.
87var _zero uintptr