| 1 | //===-- Endianness support --------------------------------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC___SUPPORT_ENDIAN_H |
| 10 | #define LLVM_LIBC_SRC___SUPPORT_ENDIAN_H |
| 11 | |
| 12 | #include "common.h" |
| 13 | |
| 14 | #include <stdint.h> |
| 15 | |
| 16 | namespace LIBC_NAMESPACE { |
| 17 | |
| 18 | // We rely on compiler preprocessor defines to allow for cross compilation. |
| 19 | #if !defined(__BYTE_ORDER__) || !defined(__ORDER_LITTLE_ENDIAN__) || \ |
| 20 | !defined(__ORDER_BIG_ENDIAN__) |
| 21 | #error "Missing preprocessor definitions for endianness detection." |
| 22 | #endif |
| 23 | |
| 24 | namespace internal { |
| 25 | |
| 26 | // Converts uint8_t, uint16_t, uint32_t, uint64_t to its big or little endian |
| 27 | // counterpart. |
| 28 | // We use explicit template specialization: |
| 29 | // - to prevent accidental integer promotion. |
| 30 | // - to prevent fallback in (unlikely) case of middle-endianness. |
| 31 | |
| 32 | template <unsigned ORDER> struct Endian { |
| 33 | static constexpr const bool IS_LITTLE = ORDER == __ORDER_LITTLE_ENDIAN__; |
| 34 | static constexpr const bool IS_BIG = ORDER == __ORDER_BIG_ENDIAN__; |
| 35 | template <typename T> LIBC_INLINE static T to_big_endian(T value); |
| 36 | template <typename T> LIBC_INLINE static T to_little_endian(T value); |
| 37 | }; |
| 38 | |
| 39 | // Little Endian specializations |
| 40 | template <> |
| 41 | template <> |
| 42 | LIBC_INLINE uint8_t |
| 43 | Endian<__ORDER_LITTLE_ENDIAN__>::to_big_endian<uint8_t>(uint8_t v) { |
| 44 | return v; |
| 45 | } |
| 46 | template <> |
| 47 | template <> |
| 48 | LIBC_INLINE uint8_t |
| 49 | Endian<__ORDER_LITTLE_ENDIAN__>::to_little_endian<uint8_t>(uint8_t v) { |
| 50 | return v; |
| 51 | } |
| 52 | template <> |
| 53 | template <> |
| 54 | LIBC_INLINE uint16_t |
| 55 | Endian<__ORDER_LITTLE_ENDIAN__>::to_big_endian<uint16_t>(uint16_t v) { |
| 56 | return __builtin_bswap16(v); |
| 57 | } |
| 58 | template <> |
| 59 | template <> |
| 60 | LIBC_INLINE uint16_t |
| 61 | Endian<__ORDER_LITTLE_ENDIAN__>::to_little_endian<uint16_t>(uint16_t v) { |
| 62 | return v; |
| 63 | } |
| 64 | template <> |
| 65 | template <> |
| 66 | LIBC_INLINE uint32_t |
| 67 | Endian<__ORDER_LITTLE_ENDIAN__>::to_big_endian<uint32_t>(uint32_t v) { |
| 68 | return __builtin_bswap32(v); |
| 69 | } |
| 70 | template <> |
| 71 | template <> |
| 72 | LIBC_INLINE uint32_t |
| 73 | Endian<__ORDER_LITTLE_ENDIAN__>::to_little_endian<uint32_t>(uint32_t v) { |
| 74 | return v; |
| 75 | } |
| 76 | template <> |
| 77 | template <> |
| 78 | LIBC_INLINE uint64_t |
| 79 | Endian<__ORDER_LITTLE_ENDIAN__>::to_big_endian<uint64_t>(uint64_t v) { |
| 80 | return __builtin_bswap64(v); |
| 81 | } |
| 82 | template <> |
| 83 | template <> |
| 84 | LIBC_INLINE uint64_t |
| 85 | Endian<__ORDER_LITTLE_ENDIAN__>::to_little_endian<uint64_t>(uint64_t v) { |
| 86 | return v; |
| 87 | } |
| 88 | |
| 89 | // Big Endian specializations |
| 90 | template <> |
| 91 | template <> |
| 92 | LIBC_INLINE uint8_t |
| 93 | Endian<__ORDER_BIG_ENDIAN__>::to_big_endian<uint8_t>(uint8_t v) { |
| 94 | return v; |
| 95 | } |
| 96 | template <> |
| 97 | template <> |
| 98 | LIBC_INLINE uint8_t |
| 99 | Endian<__ORDER_BIG_ENDIAN__>::to_little_endian<uint8_t>(uint8_t v) { |
| 100 | return v; |
| 101 | } |
| 102 | template <> |
| 103 | template <> |
| 104 | LIBC_INLINE uint16_t |
| 105 | Endian<__ORDER_BIG_ENDIAN__>::to_big_endian<uint16_t>(uint16_t v) { |
| 106 | return v; |
| 107 | } |
| 108 | template <> |
| 109 | template <> |
| 110 | LIBC_INLINE uint16_t |
| 111 | Endian<__ORDER_BIG_ENDIAN__>::to_little_endian<uint16_t>(uint16_t v) { |
| 112 | return __builtin_bswap16(v); |
| 113 | } |
| 114 | template <> |
| 115 | template <> |
| 116 | LIBC_INLINE uint32_t |
| 117 | Endian<__ORDER_BIG_ENDIAN__>::to_big_endian<uint32_t>(uint32_t v) { |
| 118 | return v; |
| 119 | } |
| 120 | template <> |
| 121 | template <> |
| 122 | LIBC_INLINE uint32_t |
| 123 | Endian<__ORDER_BIG_ENDIAN__>::to_little_endian<uint32_t>(uint32_t v) { |
| 124 | return __builtin_bswap32(v); |
| 125 | } |
| 126 | template <> |
| 127 | template <> |
| 128 | LIBC_INLINE uint64_t |
| 129 | Endian<__ORDER_BIG_ENDIAN__>::to_big_endian<uint64_t>(uint64_t v) { |
| 130 | return v; |
| 131 | } |
| 132 | template <> |
| 133 | template <> |
| 134 | LIBC_INLINE uint64_t |
| 135 | Endian<__ORDER_BIG_ENDIAN__>::to_little_endian<uint64_t>(uint64_t v) { |
| 136 | return __builtin_bswap64(v); |
| 137 | } |
| 138 | |
| 139 | } // namespace internal |
| 140 | |
| 141 | using Endian = internal::Endian<__BYTE_ORDER__>; |
| 142 | |
| 143 | } // namespace LIBC_NAMESPACE |
| 144 | |
| 145 | #endif // LLVM_LIBC_SRC___SUPPORT_ENDIAN_H |
| 146 |