// Copyright 2018 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.

// +build freebsd netbsd

package unix

import (

	"strings"

	"unsafe"

)

// Derive extattr namespace and attribute name

func xattrnamespace(fullattr string) (ns int, attr string, err error) {

	s := strings.IndexByte(fullattr, '.')

	if s == -1 {

		return -1, "", ENOATTR

	}

	namespace := fullattr[0:s]

	attr = fullattr[s+1:]

	switch namespace {

	case "user":

		return EXTATTR_NAMESPACE_USER, attr, nil

	case "system":

		return EXTATTR_NAMESPACE_SYSTEM, attr, nil

	default:

		return -1, "", ENOATTR

	}

}

func initxattrdest(dest []byte, idx int) (d unsafe.Pointer) {

	if len(dest) > idx {

		return unsafe.Pointer(&dest[idx])

	} else {

		return unsafe.Pointer(_zero)

	}

}

// FreeBSD and NetBSD implement their own syscalls to handle extended attributes

func Getxattr(file string, attr string, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsize := len(dest)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return -1, err

	}

	return ExtattrGetFile(file, nsid, a, uintptr(d), destsize)

}

func Fgetxattr(fd int, attr string, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsize := len(dest)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return -1, err

	}

	return ExtattrGetFd(fd, nsid, a, uintptr(d), destsize)

}

func Lgetxattr(link string, attr string, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsize := len(dest)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return -1, err

	}

	return ExtattrGetLink(link, nsid, a, uintptr(d), destsize)

}

// flags are unused on FreeBSD

func Fsetxattr(fd int, attr string, data []byte, flags int) (err error) {

	var d unsafe.Pointer

	if len(data) > 0 {

		d = unsafe.Pointer(&data[0])

	}

	datasiz := len(data)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	_, err = ExtattrSetFd(fd, nsid, a, uintptr(d), datasiz)

	return

}

func Setxattr(file string, attr string, data []byte, flags int) (err error) {

	var d unsafe.Pointer

	if len(data) > 0 {

		d = unsafe.Pointer(&data[0])

	}

	datasiz := len(data)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	_, err = ExtattrSetFile(file, nsid, a, uintptr(d), datasiz)

	return

}

func Lsetxattr(link string, attr string, data []byte, flags int) (err error) {

	var d unsafe.Pointer

	if len(data) > 0 {

		d = unsafe.Pointer(&data[0])

	}

	datasiz := len(data)

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	_, err = ExtattrSetLink(link, nsid, a, uintptr(d), datasiz)

	return

}

func Removexattr(file string, attr string) (err error) {

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	err = ExtattrDeleteFile(file, nsid, a)

	return

}

func Fremovexattr(fd int, attr string) (err error) {

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	err = ExtattrDeleteFd(fd, nsid, a)

	return

}

func Lremovexattr(link string, attr string) (err error) {

	nsid, a, err := xattrnamespace(attr)

	if err != nil {

		return

	}

	err = ExtattrDeleteLink(link, nsid, a)

	return

}

func Listxattr(file string, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsiz := len(dest)

	// FreeBSD won't allow you to list xattrs from multiple namespaces

	s := 0

	for _, nsid := range [...]int{EXTATTR_NAMESPACE_USER, EXTATTR_NAMESPACE_SYSTEM} {

		stmp, e := ExtattrListFile(file, nsid, uintptr(d), destsiz)

		/* Errors accessing system attrs are ignored so that

		 * we can implement the Linux-like behavior of omitting errors that

		 * we don't have read permissions on

		 *

		 * Linux will still error if we ask for user attributes on a file that

		 * we don't have read permissions on, so don't ignore those errors

		 */

		if e != nil && e == EPERM && nsid != EXTATTR_NAMESPACE_USER {

			continue

		} else if e != nil {

			return s, e

		}

		s += stmp

		destsiz -= s

		if destsiz < 0 {

			destsiz = 0

		}

		d = initxattrdest(dest, s)

	}

	return s, nil

}

func Flistxattr(fd int, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsiz := len(dest)

	s := 0

	for _, nsid := range [...]int{EXTATTR_NAMESPACE_USER, EXTATTR_NAMESPACE_SYSTEM} {

		stmp, e := ExtattrListFd(fd, nsid, uintptr(d), destsiz)

		if e != nil && e == EPERM && nsid != EXTATTR_NAMESPACE_USER {

			continue

		} else if e != nil {

			return s, e

		}

		s += stmp

		destsiz -= s

		if destsiz < 0 {

			destsiz = 0

		}

		d = initxattrdest(dest, s)

	}

	return s, nil

}

func Llistxattr(link string, dest []byte) (sz int, err error) {

	d := initxattrdest(dest, 0)

	destsiz := len(dest)

	s := 0

	for _, nsid := range [...]int{EXTATTR_NAMESPACE_USER, EXTATTR_NAMESPACE_SYSTEM} {

		stmp, e := ExtattrListLink(link, nsid, uintptr(d), destsiz)

		if e != nil && e == EPERM && nsid != EXTATTR_NAMESPACE_USER {

			continue

		} else if e != nil {

			return s, e

		}

		s += stmp

		destsiz -= s

		if destsiz < 0 {

			destsiz = 0

		}

		d = initxattrdest(dest, s)

	}

	return s, nil

}