util/endian: add package with const for whether platform is big endian

util/endian/big.go

@@ -0,0 +1,10 @@
+// Copyright (c) 2020 Tailscale Inc & 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 mips mips64 ppc64 s390x
+
+package endian
+
+// Big is whether the current platform is big endian.
+const Big = true

util/endian/endian.go

@@ -0,0 +1,6 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package endian exports a constant about whether the machine is big endian.
+package endian

util/endian/little.go

@@ -0,0 +1,10 @@
+// Copyright (c) 2020 Tailscale Inc & 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 386 amd64 arm arm64 mips64le mipsle ppc64le riscv64 wasm
+
+package endian
+
+// Big is whether the current platform is big endian.
+const Big = false