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     sys::swapByteOrder(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   packed_endian_specific_integral &operator+=(value_type newValue) {
  97     *this = *this + newValue;
  98     return *this;
  99   }
 100
 101   packed_endian_specific_integral &operator-=(value_type newValue) {
 102     *this = *this - newValue;
 103     return *this;
 104   }
 105
 106 private:
 107   AlignedCharArray<PickAlignment<value_type, alignment>::value,
 108                    sizeof(value_type)> Value;
 109
 110 public:
 111   struct ref {
 112     explicit ref(void *Ptr) : Ptr(Ptr) {}
 113
 114     operator value_type() const {
 115       return endian::read<value_type, endian, alignment>(Ptr);
 116     }
 117
 118     void operator=(value_type NewValue) {
 119       endian::write<value_type, endian, alignment>(Ptr, NewValue);
 120     }
 121
 122   private:
 123     void *Ptr;
 124   };
 125 };
 126
 127 } // end namespace detail
 128
 129 typedef detail::packed_endian_specific_integral
 130                   <uint16_t, little, unaligned> ulittle16_t;
 131 typedef detail::packed_endian_specific_integral
 132                   <uint32_t, little, unaligned> ulittle32_t;
 133 typedef detail::packed_endian_specific_integral
 134                   <uint64_t, little, unaligned> ulittle64_t;
 135
 136 typedef detail::packed_endian_specific_integral
 137                    <int16_t, little, unaligned> little16_t;
 138 typedef detail::packed_endian_specific_integral
 139                    <int32_t, little, unaligned> little32_t;
 140 typedef detail::packed_endian_specific_integral
 141                    <int64_t, little, unaligned> little64_t;
 142
 143 typedef detail::packed_endian_specific_integral
 144                     <uint16_t, little, aligned> aligned_ulittle16_t;
 145 typedef detail::packed_endian_specific_integral
 146                     <uint32_t, little, aligned> aligned_ulittle32_t;
 147 typedef detail::packed_endian_specific_integral
 148                     <uint64_t, little, aligned> aligned_ulittle64_t;
 149
 150 typedef detail::packed_endian_specific_integral
 151                      <int16_t, little, aligned> aligned_little16_t;
 152 typedef detail::packed_endian_specific_integral
 153                      <int32_t, little, aligned> aligned_little32_t;
 154 typedef detail::packed_endian_specific_integral
 155                      <int64_t, little, aligned> aligned_little64_t;
 156
 157 typedef detail::packed_endian_specific_integral
 158                   <uint16_t, big, unaligned>    ubig16_t;
 159 typedef detail::packed_endian_specific_integral
 160                   <uint32_t, big, unaligned>    ubig32_t;
 161 typedef detail::packed_endian_specific_integral
 162                   <uint64_t, big, unaligned>    ubig64_t;
 163
 164 typedef detail::packed_endian_specific_integral
 165                    <int16_t, big, unaligned>    big16_t;
 166 typedef detail::packed_endian_specific_integral
 167                    <int32_t, big, unaligned>    big32_t;
 168 typedef detail::packed_endian_specific_integral
 169                    <int64_t, big, unaligned>    big64_t;
 170
 171 typedef detail::packed_endian_specific_integral
 172                     <uint16_t, big, aligned>    aligned_ubig16_t;
 173 typedef detail::packed_endian_specific_integral
 174                     <uint32_t, big, aligned>    aligned_ubig32_t;
 175 typedef detail::packed_endian_specific_integral
 176                     <uint64_t, big, aligned>    aligned_ubig64_t;
 177
 178 typedef detail::packed_endian_specific_integral
 179                      <int16_t, big, aligned>    aligned_big16_t;
 180 typedef detail::packed_endian_specific_integral
 181                      <int32_t, big, aligned>    aligned_big32_t;
 182 typedef detail::packed_endian_specific_integral
 183                      <int64_t, big, aligned>    aligned_big64_t;
 184
 185 typedef detail::packed_endian_specific_integral
 186                   <uint16_t, native, unaligned> unaligned_uint16_t;
 187 typedef detail::packed_endian_specific_integral
 188                   <uint32_t, native, unaligned> unaligned_uint32_t;
 189 typedef detail::packed_endian_specific_integral
 190                   <uint64_t, native, unaligned> unaligned_uint64_t;
 191
 192 typedef detail::packed_endian_specific_integral
 193                    <int16_t, native, unaligned> unaligned_int16_t;
 194 typedef detail::packed_endian_specific_integral
 195                    <int32_t, native, unaligned> unaligned_int32_t;
 196 typedef detail::packed_endian_specific_integral
 197                    <int64_t, native, unaligned> unaligned_int64_t;
 198 } // end namespace llvm
 199 } // end namespace support
 200
 201 #endif