// Copyright 2009 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.

//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos

// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos

// Package unix contains an interface to the low-level operating system

// primitives. OS details vary depending on the underlying system, and

// by default, godoc will display OS-specific documentation for the current

// system. If you want godoc to display OS documentation for another

// system, set $GOOS and $GOARCH to the desired system. For example, if

// you want to view documentation for freebsd/arm on linux/amd64, set $GOOS

// to freebsd and $GOARCH to arm.

//

// The primary use of this package is inside other packages that provide a more

// portable interface to the system, such as "os", "time" and "net".  Use

// those packages rather than this one if you can.

//

// For details of the functions and data types in this package consult

// the manuals for the appropriate operating system.

//

// These calls return err == nil to indicate success; otherwise

// err represents an operating system error describing the failure and

// holds a value of type syscall.Errno.

package unix // import "golang.org/x/sys/unix"

import (

	"bytes"

	"strings"

	"unsafe"

)

// ByteSliceFromString returns a NUL-terminated slice of bytes

// containing the text of s. If s contains a NUL byte at any

// location, it returns (nil, EINVAL).

func ByteSliceFromString(s string) ([]byte, error) {

	if strings.IndexByte(s, 0) != -1 {

		return nil, EINVAL

	}

	a := make([]byte, len(s)+1)

	copy(a, s)

	return a, nil

}

// BytePtrFromString returns a pointer to a NUL-terminated array of

// bytes containing the text of s. If s contains a NUL byte at any

// location, it returns (nil, EINVAL).

func BytePtrFromString(s string) (*byte, error) {

	a, err := ByteSliceFromString(s)

	if err != nil {

		return nil, err

	}

	return &a[0], nil

}

// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any

// bytes after the NUL removed.

func ByteSliceToString(s []byte) string {

	if i := bytes.IndexByte(s, 0); i != -1 {

		s = s[:i]

	}

	return string(s)

}

// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.

// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated

// at a zero byte; if the zero byte is not present, the program may crash.

func BytePtrToString(p *byte) string {

	if p == nil {

		return ""

	}

	if *p == 0 {

		return ""

	}

	// Find NUL terminator.

	n := 0

	for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {

		ptr = unsafe.Pointer(uintptr(ptr) + 1)

	}

}

// Single-word zero for use when we need a valid pointer to 0 bytes.

var _zero uintptr