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// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
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	"golang.org/x/sys/internal/unsafeheader"
33)
34
35// ByteSliceFromString returns a NUL-terminated slice of bytes
36// containing the text of s. If s contains a NUL byte at any
37// location, it returns (nil, EINVAL).
38func ByteSliceFromString(s string) ([]byte, error) {
39	if strings.IndexByte(s, 0) != -1 {
40		return nil, EINVAL
41	}
42	a := make([]byte, len(s)+1)
43	copy(a, s)
44	return a, nil
45}
46
47// BytePtrFromString returns a pointer to a NUL-terminated array of
48// bytes containing the text of s. If s contains a NUL byte at any
49// location, it returns (nil, EINVAL).
50func BytePtrFromString(s string) (*byte, error) {
51	a, err := ByteSliceFromString(s)
52	if err != nil {
53		return nil, err
54	}
55	return &a[0], nil
56}
57
58// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any
59// bytes after the NUL removed.
60func ByteSliceToString(s []byte) string {
61	if i := bytes.IndexByte(s, 0); i != -1 {
62		s = s[:i]
63	}
64	return string(s)
65}
66
67// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.
68// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated
69// at a zero byte; if the zero byte is not present, the program may crash.
70func BytePtrToString(p *byte) string {
71	if p == nil {
72		return ""
73	}
74	if *p == 0 {
75		return ""
76	}
77
78	// Find NUL terminator.
79	n := 0
80	for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {
81		ptr = unsafe.Pointer(uintptr(ptr) + 1)
82	}
83
84	var s []byte
85	h := (*unsafeheader.Slice)(unsafe.Pointer(&s))
86	h.Data = unsafe.Pointer(p)
87	h.Len = n
88	h.Cap = n
89
90	return string(s)
91}
92
93// Single-word zero for use when we need a valid pointer to 0 bytes.
94var _zero uintptr
95