1 | // Copyright (c) 2013 Austin T. Clements. All rights reserved. |
2 | // Use of this source code is governed by an MIT license |
3 | // that can be found in the LICENSE file. |
4 | |
5 | #ifndef _ELFPP_COMMON_HH_ |
6 | #define _ELFPP_COMMON_HH_ |
7 | |
8 | #define ELFPP_BEGIN_NAMESPACE namespace elf { |
9 | #define ELFPP_END_NAMESPACE } |
10 | #define ELFPP_BEGIN_INTERNAL namespace internal { |
11 | #define ELFPP_END_INTERNAL } |
12 | |
13 | #include <cstdint> |
14 | |
15 | ELFPP_BEGIN_NAMESPACE |
16 | |
17 | /** |
18 | * A byte ordering. |
19 | */ |
20 | enum class byte_order |
21 | { |
22 | native, |
23 | lsb, |
24 | msb |
25 | }; |
26 | |
27 | /** |
28 | * Return either byte_order::lsb or byte_order::msb. If the argument |
29 | * is byte_order::native, it will be resolved to whatever the native |
30 | * byte order is. |
31 | */ |
32 | static inline byte_order |
33 | resolve_order(byte_order o) |
34 | { |
35 | static const union |
36 | { |
37 | int i; |
38 | char c[sizeof(int)]; |
39 | } test = {1}; |
40 | |
41 | if (o == byte_order::native) |
42 | return test.c[0] == 1 ? byte_order::lsb : byte_order::msb; |
43 | return o; |
44 | } |
45 | |
46 | /** |
47 | * Return v converted from one byte order to another. |
48 | */ |
49 | template<typename T> |
50 | T |
51 | swizzle(T v, byte_order from, byte_order to) |
52 | { |
53 | static_assert(sizeof(T) == 1 || |
54 | sizeof(T) == 2 || |
55 | sizeof(T) == 4 || |
56 | sizeof(T) == 8, |
57 | "cannot swizzle type" ); |
58 | |
59 | from = resolve_order(from); |
60 | to = resolve_order(to); |
61 | |
62 | if (from == to) |
63 | return v; |
64 | |
65 | switch (sizeof(T)) { |
66 | case 1: |
67 | return v; |
68 | case 2: { |
69 | std::uint16_t x = (std::uint16_t)v; |
70 | return (T)(((x&0xFF) << 8) | (x >> 8)); |
71 | } |
72 | case 4: |
73 | return (T)__builtin_bswap32((std::uint32_t)v); |
74 | case 8: |
75 | return (T)__builtin_bswap64((std::uint64_t)v); |
76 | } |
77 | } |
78 | |
79 | ELFPP_BEGIN_INTERNAL |
80 | |
81 | /** |
82 | * OrderPick selects between Native, LSB, and MSB based on ord. |
83 | */ |
84 | template<byte_order ord, typename Native, typename LSB, typename MSB> |
85 | struct OrderPick; |
86 | |
87 | template<typename Native, typename LSB, typename MSB> |
88 | struct OrderPick<byte_order::native, Native, LSB, MSB> |
89 | { |
90 | typedef Native T; |
91 | }; |
92 | |
93 | template<typename Native, typename LSB, typename MSB> |
94 | struct OrderPick<byte_order::lsb, Native, LSB, MSB> |
95 | { |
96 | typedef LSB T; |
97 | }; |
98 | |
99 | template<typename Native, typename LSB, typename MSB> |
100 | struct OrderPick<byte_order::msb, Native, LSB, MSB> |
101 | { |
102 | typedef MSB T; |
103 | }; |
104 | |
105 | ELFPP_END_INTERNAL |
106 | |
107 | ELFPP_END_NAMESPACE |
108 | |
109 | #endif |
110 | |