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      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 #include "llvm/Support/type_traits.h"
     21 
     22 namespace llvm {
     23 namespace support {
     24 enum endianness {big, little, native};
     25 
     26 // These are named values for common alignments.
     27 enum {aligned = 0, unaligned = 1};
     28 
     29 namespace detail {
     30   /// \brief ::value is either alignment, or alignof(T) if alignment is 0.
     31   template<class T, int alignment>
     32   struct PickAlignment {
     33     enum {value = alignment == 0 ? AlignOf<T>::Alignment : alignment};
     34   };
     35 } // end namespace detail
     36 
     37 namespace endian {
     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::SwapByteOrder(value);
     42   return value;
     43 }
     44 
     45 template<typename value_type,
     46          endianness endian,
     47          std::size_t alignment>
     48 inline value_type read(const void *memory) {
     49   value_type ret;
     50 
     51   memcpy(&ret,
     52          LLVM_ASSUME_ALIGNED(memory,
     53            (detail::PickAlignment<value_type, alignment>::value)),
     54          sizeof(value_type));
     55   return byte_swap<value_type, endian>(ret);
     56 }
     57 
     58 template<typename value_type,
     59          endianness endian,
     60          std::size_t alignment>
     61 inline void write(void *memory, value_type value) {
     62   value = byte_swap<value_type, endian>(value);
     63   memcpy(LLVM_ASSUME_ALIGNED(memory,
     64            (detail::PickAlignment<value_type, alignment>::value)),
     65          &value,
     66          sizeof(value_type));
     67 }
     68 } // end namespace endian
     69 
     70 namespace detail {
     71 template<typename value_type,
     72          endianness endian,
     73          std::size_t alignment>
     74 struct packed_endian_specific_integral {
     75   operator value_type() const {
     76     return endian::read<value_type, endian, alignment>(
     77       (const void*)Value.buffer);
     78   }
     79 
     80   void operator=(value_type newValue) {
     81     endian::write<value_type, endian, alignment>(
     82       (void*)Value.buffer, newValue);
     83   }
     84 
     85 private:
     86   AlignedCharArray<PickAlignment<value_type, alignment>::value,
     87                    sizeof(value_type)> Value;
     88 };
     89 } // end namespace detail
     90 
     91 typedef detail::packed_endian_specific_integral
     92                   <uint8_t, little, unaligned>  ulittle8_t;
     93 typedef detail::packed_endian_specific_integral
     94                   <uint16_t, little, unaligned> ulittle16_t;
     95 typedef detail::packed_endian_specific_integral
     96                   <uint32_t, little, unaligned> ulittle32_t;
     97 typedef detail::packed_endian_specific_integral
     98                   <uint64_t, little, unaligned> ulittle64_t;
     99 
    100 typedef detail::packed_endian_specific_integral
    101                    <int8_t, little, unaligned>  little8_t;
    102 typedef detail::packed_endian_specific_integral
    103                    <int16_t, little, unaligned> little16_t;
    104 typedef detail::packed_endian_specific_integral
    105                    <int32_t, little, unaligned> little32_t;
    106 typedef detail::packed_endian_specific_integral
    107                    <int64_t, little, unaligned> little64_t;
    108 
    109 typedef detail::packed_endian_specific_integral
    110                     <uint8_t, little, aligned>  aligned_ulittle8_t;
    111 typedef detail::packed_endian_specific_integral
    112                     <uint16_t, little, aligned> aligned_ulittle16_t;
    113 typedef detail::packed_endian_specific_integral
    114                     <uint32_t, little, aligned> aligned_ulittle32_t;
    115 typedef detail::packed_endian_specific_integral
    116                     <uint64_t, little, aligned> aligned_ulittle64_t;
    117 
    118 typedef detail::packed_endian_specific_integral
    119                      <int8_t, little, aligned>  aligned_little8_t;
    120 typedef detail::packed_endian_specific_integral
    121                      <int16_t, little, aligned> aligned_little16_t;
    122 typedef detail::packed_endian_specific_integral
    123                      <int32_t, little, aligned> aligned_little32_t;
    124 typedef detail::packed_endian_specific_integral
    125                      <int64_t, little, aligned> aligned_little64_t;
    126 
    127 typedef detail::packed_endian_specific_integral
    128                   <uint8_t, big, unaligned>     ubig8_t;
    129 typedef detail::packed_endian_specific_integral
    130                   <uint16_t, big, unaligned>    ubig16_t;
    131 typedef detail::packed_endian_specific_integral
    132                   <uint32_t, big, unaligned>    ubig32_t;
    133 typedef detail::packed_endian_specific_integral
    134                   <uint64_t, big, unaligned>    ubig64_t;
    135 
    136 typedef detail::packed_endian_specific_integral
    137                    <int8_t, big, unaligned>     big8_t;
    138 typedef detail::packed_endian_specific_integral
    139                    <int16_t, big, unaligned>    big16_t;
    140 typedef detail::packed_endian_specific_integral
    141                    <int32_t, big, unaligned>    big32_t;
    142 typedef detail::packed_endian_specific_integral
    143                    <int64_t, big, unaligned>    big64_t;
    144 
    145 typedef detail::packed_endian_specific_integral
    146                     <uint8_t, big, aligned>     aligned_ubig8_t;
    147 typedef detail::packed_endian_specific_integral
    148                     <uint16_t, big, aligned>    aligned_ubig16_t;
    149 typedef detail::packed_endian_specific_integral
    150                     <uint32_t, big, aligned>    aligned_ubig32_t;
    151 typedef detail::packed_endian_specific_integral
    152                     <uint64_t, big, aligned>    aligned_ubig64_t;
    153 
    154 typedef detail::packed_endian_specific_integral
    155                      <int8_t, big, aligned>     aligned_big8_t;
    156 typedef detail::packed_endian_specific_integral
    157                      <int16_t, big, aligned>    aligned_big16_t;
    158 typedef detail::packed_endian_specific_integral
    159                      <int32_t, big, aligned>    aligned_big32_t;
    160 typedef detail::packed_endian_specific_integral
    161                      <int64_t, big, aligned>    aligned_big64_t;
    162 
    163 typedef detail::packed_endian_specific_integral
    164                   <uint16_t, native, unaligned> unaligned_uint16_t;
    165 typedef detail::packed_endian_specific_integral
    166                   <uint32_t, native, unaligned> unaligned_uint32_t;
    167 typedef detail::packed_endian_specific_integral
    168                   <uint64_t, native, unaligned> unaligned_uint64_t;
    169 
    170 typedef detail::packed_endian_specific_integral
    171                    <int16_t, native, unaligned> unaligned_int16_t;
    172 typedef detail::packed_endian_specific_integral
    173                    <int32_t, native, unaligned> unaligned_int32_t;
    174 typedef detail::packed_endian_specific_integral
    175                    <int64_t, native, unaligned> unaligned_int64_t;
    176 } // end namespace llvm
    177 } // end namespace support
    178 
    179 #endif
    180