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// Copyright (C) 2015, 2017 Luke Shumaker <lukeshu@sbcglobal.net>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
// 02110-1301 USA
package nslcd_proto
import (
"encoding/binary"
"fmt"
"io"
"net"
"reflect"
"golang.org/x/sys/unix"
)
// NslcdError represents a normal, expected error when dealing with
// the nslcd protocol. Passing invalid data to a Write operation is
// *not* an NslcdError, nor is passing a non-pointer to a Read
// operation; those are programming errors, and result in a panic().
type NslcdError string
func (o NslcdError) Error() string {
return string(o)
}
func npanic(err NslcdError) {
panic(err)
}
// An nslcdObject is an object with a different network representation
// than a naive structure.
type nslcdObject interface {
// May panic(interface{}) if given invalid data.
//
// May panic(NslcdError) if encountering a network error.
nslcdWrite(fd io.Writer)
}
// An nslcdObjectPtr is a pointer to an object with a different
// network representation than a naive structure.
type nslcdObjectPtr interface {
// May panic(NslcdError) if encountering a network error.
nslcdRead(fd io.Reader)
}
// Write an object to a stream. Any errors returned are of type
// NslcdError.
func Write(fd io.Writer, data interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
switch r := r.(type) {
case NslcdError:
err = r
default:
panic(r)
}
}
}()
write(fd, data)
return err
}
// Read an object from a stream. Any errors returned are of type
// NslcdError.
func Read(fd io.Reader, data interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
switch r := r.(type) {
case NslcdError:
err = r
default:
panic(r)
}
}
}()
read(fd, data)
return err
}
// Write an object to a stream. In the event of an error, this
// function may panic(NslcdError)! Handle it!
func write(fd io.Writer, data interface{}) {
switch data := data.(type) {
// basic data types
case nslcdObject:
data.nslcdWrite(fd)
case []byte:
if len(data) > 0 {
_, err := fd.Write(data)
if err != nil {
npanic(NslcdError(err.Error()))
}
}
case int32:
err := binary.Write(fd, binary.BigEndian, data)
if err != nil {
npanic(NslcdError(err.Error()))
}
// composite datatypes
case string:
write(fd, int32(len(data)))
write(fd, []byte(data))
case []string:
write(fd, int32(len(data)))
for _, item := range data {
write(fd, item)
}
case net.IP:
var af int32 = -1
switch len(data) {
case net.IPv4len:
af = unix.AF_INET
case net.IPv6len:
af = unix.AF_INET6
}
var bytes []byte
if af < 0 {
bytes = make([]byte, 0)
} else {
bytes = data
}
write(fd, af)
write(fd, int32(len(bytes)))
write(fd, bytes)
case []net.IP:
write(fd, int32(len(data)))
for _, item := range data {
write(fd, item)
}
default:
v := reflect.ValueOf(data)
switch v.Kind() {
case reflect.Struct:
for i, n := 0, v.NumField(); i < n; i++ {
write(fd, v.Field(i).Interface())
}
default:
panic(fmt.Sprintf("Invalid structure to write NSLCD protocol data from: %T ( %#v )", data, data))
}
}
}
// Read an object from a stream. In the event of an error, this
// function may panic(NslcdError)! Handle it!
func read(fd io.Reader, data interface{}) {
switch data := data.(type) {
// basic data types
case nslcdObjectPtr:
data.nslcdRead(fd)
case *[]byte:
if len(*data) > 0 {
_, err := io.ReadFull(fd, *data)
if err != nil {
npanic(NslcdError(err.Error()))
}
}
case *int32:
err := binary.Read(fd, binary.BigEndian, data)
if err != nil {
npanic(NslcdError(err.Error()))
}
// composite datatypes
case *string:
var len int32
read(fd, &len)
buf := make([]byte, len) // BUG(lukeshu): Read: `string` length needs sanity checked
read(fd, &buf)
*data = string(buf)
case *[]string:
var num int32
read(fd, &num)
*data = make([]string, num) // BUG(lukeshu): Read: `[]string` length needs sanity checked
for i := 0; i < int(num); i++ {
read(fd, &((*data)[i]))
}
case *net.IP:
var af int32
read(fd, &af)
var _len int32
switch af {
case unix.AF_INET:
_len = net.IPv4len
case unix.AF_INET6:
_len = net.IPv6len
default:
npanic(NslcdError(fmt.Sprintf("incorrect address family specified: %d", af)))
}
var len int32
read(fd, &len)
if len != _len {
npanic(NslcdError(fmt.Sprintf("address length incorrect: %d", len)))
}
buf := make([]byte, len)
read(fd, &buf)
*data = buf
case *[]net.IP:
var num int32
read(fd, &num)
*data = make([]net.IP, num) // BUG(lukeshu): Read: `[]net.IP` length needs sanity checked
for i := 0; i < int(num); i++ {
read(fd, &((*data)[i]))
}
default:
p := reflect.ValueOf(data)
v := reflect.Indirect(p)
if p == v || v.Kind() != reflect.Struct {
panic(fmt.Sprintf("The argument to nslcd_proto.Read() must be a pointer: %T ( %#v )", data, data))
}
for i, n := 0, v.NumField(); i < n; i++ {
read(fd, v.Field(i).Addr().Interface())
}
}
}
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