include/llvm/Support/Endian.h

   1 //===- Endian.h - Utilities for IO with endian specific data ----*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file declares generic functions to read and write endian specific data.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_SUPPORT_ENDIAN_H
  15 #define LLVM_SUPPORT_ENDIAN_H
  16
  17 #include "llvm/Support/AlignOf.h"
  18 #include "llvm/Support/Host.h"
  19 #include "llvm/Support/SwapByteOrder.h"
  20
  21 namespace llvm {
  22 namespace support {
  23 enum endianness {big, little, native};
  24
  25 // These are named values for common alignments.
  26 enum {aligned = 0, unaligned = 1};
  27
  28 namespace detail {
  29   /// \brief ::value is either alignment, or alignof(T) if alignment is 0.
  30   template<class T, int alignment>
  31   struct PickAlignment {
  32     enum {value = alignment == 0 ? AlignOf<T>::Alignment : alignment};
  33   };
  34 } // end namespace detail
  35
  36 namespace endian {
  37 /// Swap the bytes of value to match the given endianness.
  38 template<typename value_type, endianness endian>
  39 inline value_type byte_swap(value_type value) {
  40   if (endian != native && sys::IsBigEndianHost != (endian == big))
  41     return sys::getSwappedBytes(value);
  42   return value;
  43 }
  44
  45 /// Read a value of a particular endianness from memory.
  46 template<typename value_type,
  47          endianness endian,
  48          std::size_t alignment>
  49 inline value_type read(const void *memory) {
  50   value_type ret;
  51
  52   memcpy(&ret,
  53          LLVM_ASSUME_ALIGNED(memory,
  54            (detail::PickAlignment<value_type, alignment>::value)),
  55          sizeof(value_type));
  56   return byte_swap<value_type, endian>(ret);
  57 }
  58
  59 /// Read a value of a particular endianness from a buffer, and increment the
  60 /// buffer past that value.
  61 template<typename value_type, endianness endian, std::size_t alignment>
  62 inline value_type readNext(const unsigned char *&memory) {
  63   value_type ret = read<value_type, endian, alignment>(memory);
  64   memory += sizeof(value_type);
  65   return ret;
  66 }
  67
  68 /// Write a value to memory with a particular endianness.
  69 template<typename value_type,
  70          endianness endian,
  71          std::size_t alignment>
  72 inline void write(void *memory, value_type value) {
  73   value = byte_swap<value_type, endian>(value);
  74   memcpy(LLVM_ASSUME_ALIGNED(memory,
  75            (detail::PickAlignment<value_type, alignment>::value)),
  76          &value,
  77          sizeof(value_type));
  78 }
  79 } // end namespace endian
  80
  81 namespace detail {
  82 template<typename value_type,
  83          endianness endian,
  84          std::size_t alignment>
  85 struct packed_endian_specific_integral {
  86   operator value_type() const {
  87     return endian::read<value_type, endian, alignment>(
  88       (const void*)Value.buffer);
  89   }
  90
  91   void operator=(value_type newValue) {
  92     endian::write<value_type, endian, alignment>(
  93       (void*)Value.buffer, newValue);
  94   }
  95
  96 private:
  97   AlignedCharArray<PickAlignment<value_type, alignment>::value,
  98                    sizeof(value_type)> Value;
  99 };
 100 } // end namespace detail
 101
 102 typedef detail::packed_endian_specific_integral
 103                   <uint8_t, little, unaligned>  ulittle8_t;
 104 typedef detail::packed_endian_specific_integral
 105                   <uint16_t, little, unaligned> ulittle16_t;
 106 typedef detail::packed_endian_specific_integral
 107                   <uint32_t, little, unaligned> ulittle32_t;
 108 typedef detail::packed_endian_specific_integral
 109                   <uint64_t, little, unaligned> ulittle64_t;
 110
 111 typedef detail::packed_endian_specific_integral
 112                    <int8_t, little, unaligned>  little8_t;
 113 typedef detail::packed_endian_specific_integral
 114                    <int16_t, little, unaligned> little16_t;
 115 typedef detail::packed_endian_specific_integral
 116                    <int32_t, little, unaligned> little32_t;
 117 typedef detail::packed_endian_specific_integral
 118                    <int64_t, little, unaligned> little64_t;
 119
 120 typedef detail::packed_endian_specific_integral
 121                     <uint8_t, little, aligned>  aligned_ulittle8_t;
 122 typedef detail::packed_endian_specific_integral
 123                     <uint16_t, little, aligned> aligned_ulittle16_t;
 124 typedef detail::packed_endian_specific_integral
 125                     <uint32_t, little, aligned> aligned_ulittle32_t;
 126 typedef detail::packed_endian_specific_integral
 127                     <uint64_t, little, aligned> aligned_ulittle64_t;
 128
 129 typedef detail::packed_endian_specific_integral
 130                      <int8_t, little, aligned>  aligned_little8_t;
 131 typedef detail::packed_endian_specific_integral
 132                      <int16_t, little, aligned> aligned_little16_t;
 133 typedef detail::packed_endian_specific_integral
 134                      <int32_t, little, aligned> aligned_little32_t;
 135 typedef detail::packed_endian_specific_integral
 136                      <int64_t, little, aligned> aligned_little64_t;
 137
 138 typedef detail::packed_endian_specific_integral
 139                   <uint8_t, big, unaligned>     ubig8_t;
 140 typedef detail::packed_endian_specific_integral
 141                   <uint16_t, big, unaligned>    ubig16_t;
 142 typedef detail::packed_endian_specific_integral
 143                   <uint32_t, big, unaligned>    ubig32_t;
 144 typedef detail::packed_endian_specific_integral
 145                   <uint64_t, big, unaligned>    ubig64_t;
 146
 147 typedef detail::packed_endian_specific_integral
 148                    <int8_t, big, unaligned>     big8_t;
 149 typedef detail::packed_endian_specific_integral
 150                    <int16_t, big, unaligned>    big16_t;
 151 typedef detail::packed_endian_specific_integral
 152                    <int32_t, big, unaligned>    big32_t;
 153 typedef detail::packed_endian_specific_integral
 154                    <int64_t, big, unaligned>    big64_t;
 155
 156 typedef detail::packed_endian_specific_integral
 157                     <uint8_t, big, aligned>     aligned_ubig8_t;
 158 typedef detail::packed_endian_specific_integral
 159                     <uint16_t, big, aligned>    aligned_ubig16_t;
 160 typedef detail::packed_endian_specific_integral
 161                     <uint32_t, big, aligned>    aligned_ubig32_t;
 162 typedef detail::packed_endian_specific_integral
 163                     <uint64_t, big, aligned>    aligned_ubig64_t;
 164
 165 typedef detail::packed_endian_specific_integral
 166                      <int8_t, big, aligned>     aligned_big8_t;
 167 typedef detail::packed_endian_specific_integral
 168                      <int16_t, big, aligned>    aligned_big16_t;
 169 typedef detail::packed_endian_specific_integral
 170                      <int32_t, big, aligned>    aligned_big32_t;
 171 typedef detail::packed_endian_specific_integral
 172                      <int64_t, big, aligned>    aligned_big64_t;
 173
 174 typedef detail::packed_endian_specific_integral
 175                   <uint16_t, native, unaligned> unaligned_uint16_t;
 176 typedef detail::packed_endian_specific_integral
 177                   <uint32_t, native, unaligned> unaligned_uint32_t;
 178 typedef detail::packed_endian_specific_integral
 179                   <uint64_t, native, unaligned> unaligned_uint64_t;
 180
 181 typedef detail::packed_endian_specific_integral
 182                    <int16_t, native, unaligned> unaligned_int16_t;
 183 typedef detail::packed_endian_specific_integral
 184                    <int32_t, native, unaligned> unaligned_int32_t;
 185 typedef detail::packed_endian_specific_integral
 186                    <int64_t, native, unaligned> unaligned_int64_t;
 187 } // end namespace llvm
 188 } // end namespace support
 189
 190 #endif