include/llvm/Support/SwapByteOrder.h

   1 //===- SwapByteOrder.h - Generic and optimized byte swaps -------*- 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 // This file declares generic and optimized functions to swap the byte order of
  10 // an integral type.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_SUPPORT_SWAPBYTEORDER_H
  15 #define LLVM_SUPPORT_SWAPBYTEORDER_H
  16
  17 #include "llvm/Support/Compiler.h"
  18 #include "llvm/Support/DataTypes.h"
  19 #include <cstddef>
  20 #include <type_traits>
  21 #if defined(_MSC_VER) && !defined(_DEBUG)
  22 #include <stdlib.h>
  23 #endif
  24
  25 #if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__)
  26 #include <endian.h>
  27 #elif defined(_AIX)
  28 #include <sys/machine.h>
  29 #elif defined(__sun)
  30 /* Solaris provides _BIG_ENDIAN/_LITTLE_ENDIAN selector in sys/types.h */
  31 #include <sys/types.h>
  32 #define BIG_ENDIAN 4321
  33 #define LITTLE_ENDIAN 1234
  34 #if defined(_BIG_ENDIAN)
  35 #define BYTE_ORDER BIG_ENDIAN
  36 #else
  37 #define BYTE_ORDER LITTLE_ENDIAN
  38 #endif
  39 #else
  40 #if !defined(BYTE_ORDER) && !defined(_WIN32)
  41 #include <machine/endian.h>
  42 #endif
  43 #endif
  44
  45 namespace llvm {
  46 namespace sys {
  47
  48 #if defined(BYTE_ORDER) && defined(BIG_ENDIAN) && BYTE_ORDER == BIG_ENDIAN
  49 constexpr bool IsBigEndianHost = true;
  50 #else
  51 constexpr bool IsBigEndianHost = false;
  52 #endif
  53
  54 static const bool IsLittleEndianHost = !IsBigEndianHost;
  55
  56 /// SwapByteOrder_16 - This function returns a byte-swapped representation of
  57 /// the 16-bit argument.
  58 inline uint16_t SwapByteOrder_16(uint16_t value) {
  59 #if defined(_MSC_VER) && !defined(_DEBUG)
  60   // The DLL version of the runtime lacks these functions (bug!?), but in a
  61   // release build they're replaced with BSWAP instructions anyway.
  62   return _byteswap_ushort(value);
  63 #else
  64   uint16_t Hi = value << 8;
  65   uint16_t Lo = value >> 8;
  66   return Hi | Lo;
  67 #endif
  68 }
  69
  70 /// This function returns a byte-swapped representation of the 32-bit argument.
  71 inline uint32_t SwapByteOrder_32(uint32_t value) {
  72 #if defined(__llvm__) || (defined(__GNUC__) && !defined(__ICC))
  73   return __builtin_bswap32(value);
  74 #elif defined(_MSC_VER) && !defined(_DEBUG)
  75   return _byteswap_ulong(value);
  76 #else
  77   uint32_t Byte0 = value & 0x000000FF;
  78   uint32_t Byte1 = value & 0x0000FF00;
  79   uint32_t Byte2 = value & 0x00FF0000;
  80   uint32_t Byte3 = value & 0xFF000000;
  81   return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
  82 #endif
  83 }
  84
  85 /// This function returns a byte-swapped representation of the 64-bit argument.
  86 inline uint64_t SwapByteOrder_64(uint64_t value) {
  87 #if defined(__llvm__) || (defined(__GNUC__) && !defined(__ICC))
  88   return __builtin_bswap64(value);
  89 #elif defined(_MSC_VER) && !defined(_DEBUG)
  90   return _byteswap_uint64(value);
  91 #else
  92   uint64_t Hi = SwapByteOrder_32(uint32_t(value));
  93   uint32_t Lo = SwapByteOrder_32(uint32_t(value >> 32));
  94   return (Hi << 32) | Lo;
  95 #endif
  96 }
  97
  98 inline unsigned char  getSwappedBytes(unsigned char C) { return C; }
  99 inline   signed char  getSwappedBytes(signed char C) { return C; }
 100 inline          char  getSwappedBytes(char C) { return C; }
 101
 102 inline unsigned short getSwappedBytes(unsigned short C) { return SwapByteOrder_16(C); }
 103 inline   signed short getSwappedBytes(  signed short C) { return SwapByteOrder_16(C); }
 104
 105 inline unsigned int   getSwappedBytes(unsigned int   C) { return SwapByteOrder_32(C); }
 106 inline   signed int   getSwappedBytes(  signed int   C) { return SwapByteOrder_32(C); }
 107
 108 #if __LONG_MAX__ == __INT_MAX__
 109 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_32(C); }
 110 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_32(C); }
 111 #elif __LONG_MAX__ == __LONG_LONG_MAX__
 112 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_64(C); }
 113 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_64(C); }
 114 #else
 115 #error "Unknown long size!"
 116 #endif
 117
 118 inline unsigned long long getSwappedBytes(unsigned long long C) {
 119   return SwapByteOrder_64(C);
 120 }
 121 inline signed long long getSwappedBytes(signed long long C) {
 122   return SwapByteOrder_64(C);
 123 }
 124
 125 inline float getSwappedBytes(float C) {
 126   union {
 127     uint32_t i;
 128     float f;
 129   } in, out;
 130   in.f = C;
 131   out.i = SwapByteOrder_32(in.i);
 132   return out.f;
 133 }
 134
 135 inline double getSwappedBytes(double C) {
 136   union {
 137     uint64_t i;
 138     double d;
 139   } in, out;
 140   in.d = C;
 141   out.i = SwapByteOrder_64(in.i);
 142   return out.d;
 143 }
 144
 145 template <typename T>
 146 inline typename std::enable_if<std::is_enum<T>::value, T>::type
 147 getSwappedBytes(T C) {
 148   return static_cast<T>(
 149       getSwappedBytes(static_cast<typename std::underlying_type<T>::type>(C)));
 150 }
 151
 152 template<typename T>
 153 inline void swapByteOrder(T &Value) {
 154   Value = getSwappedBytes(Value);
 155 }
 156
 157 } // end namespace sys
 158 } // end namespace llvm
 159
 160 #endif