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	"golang.org/x/sys/internal/unsafeheader"
34)
35
36// ByteSliceFromString returns a NUL-terminated slice of bytes
37// containing the text of s. If s contains a NUL byte at any
38// location, it returns (nil, EINVAL).
39func ByteSliceFromString(s string) ([]byte, error) {
40	if strings.IndexByte(s, 0) != -1 {
41		return nil, EINVAL
42	}
43	a := make([]byte, len(s)+1)
44	copy(a, s)
45	return a, nil
46}
47
48// BytePtrFromString returns a pointer to a NUL-terminated array of
49// bytes containing the text of s. If s contains a NUL byte at any
50// location, it returns (nil, EINVAL).
51func BytePtrFromString(s string) (*byte, error) {
52	a, err := ByteSliceFromString(s)
53	if err != nil {
54		return nil, err
55	}
56	return &a[0], nil
57}
58
59// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any
60// bytes after the NUL removed.
61func ByteSliceToString(s []byte) string {
62	if i := bytes.IndexByte(s, 0); i != -1 {
63		s = s[:i]
64	}
65	return string(s)
66}
67
68// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.
69// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated
70// at a zero byte; if the zero byte is not present, the program may crash.
71func BytePtrToString(p *byte) string {
72	if p == nil {
73		return ""
74	}
75	if *p == 0 {
76		return ""
77	}
78
79	// Find NUL terminator.
80	n := 0
81	for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {
82		ptr = unsafe.Pointer(uintptr(ptr) + 1)
83	}
84
85	var s []byte
86	h := (*unsafeheader.Slice)(unsafe.Pointer(&s))
87	h.Data = unsafe.Pointer(p)
88	h.Len = n
89	h.Cap = n
90
91	return string(s)
92}
93
94// Single-word zero for use when we need a valid pointer to 0 bytes.
95var _zero uintptr
96