1// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package cpu
6
7import (
8	"runtime"
9)
10
11// byteOrder is a subset of encoding/binary.ByteOrder.
12type byteOrder interface {
13	Uint32([]byte) uint32
14	Uint64([]byte) uint64
15}
16
17type littleEndian struct{}
18type bigEndian struct{}
19
20func (littleEndian) Uint32(b []byte) uint32 {
21	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
22	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
23}
24
25func (littleEndian) Uint64(b []byte) uint64 {
26	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
27	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
28		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
29}
30
31func (bigEndian) Uint32(b []byte) uint32 {
32	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
33	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
34}
35
36func (bigEndian) Uint64(b []byte) uint64 {
37	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
38	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
39		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
40}
41
42// hostByteOrder returns littleEndian on little-endian machines and
43// bigEndian on big-endian machines.
44func hostByteOrder() byteOrder {
45	switch runtime.GOARCH {
46	case "386", "amd64", "amd64p32",
47		"alpha",
48		"arm", "arm64",
49		"mipsle", "mips64le", "mips64p32le",
50		"nios2",
51		"ppc64le",
52		"riscv", "riscv64",
53		"sh":
54		return littleEndian{}
55	case "armbe", "arm64be",
56		"m68k",
57		"mips", "mips64", "mips64p32",
58		"ppc", "ppc64",
59		"s390", "s390x",
60		"shbe",
61		"sparc", "sparc64":
62		return bigEndian{}
63	}
64	panic("unknown architecture")
65}
66