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/*
* Copyright (c) 2017 by Farsight Security, Inc.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
package nmsg
// The nmsg C library renders checksums in network byte order before presenting
// them to the protobuf-c library as uint32 values. While Go's encoding/binary
// library can format and parse uint32 values as BigEndian or LittleEndian byte
// arrays, this is not sufficient to calculate an integer that will represent
// a BigEndian (network) byte array in the host's native byte order. This
// requires determining the host's byte order, a task which Go's type system
// makes cumbersome.
//
// This file uses the "unsafe" package to defeat Go's type system for the
// purposes of determining whether the package is running on a BigEndian or
// LittleEndian machine, and uses this information to implement htonl.
import (
"encoding/binary"
"unsafe"
)
var hostEndian binary.ByteOrder
func init() {
n := uint32(1)
b := *(*[4]byte)(unsafe.Pointer(&n))
if b[0] == 1 {
hostEndian = binary.LittleEndian
} else {
hostEndian = binary.BigEndian
}
}
func htonl(n uint32) uint32 {
var buf [4]byte
hostEndian.PutUint32(buf[:], n)
return binary.BigEndian.Uint32(buf[:])
}
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