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   1 /*
   2  * unaligned.h
   3  *
   4  * Inline functions for unaligned memory accesses.
   5  *
   6  * Author:      Eric Biggers
   7  * Year:        2014, 2015
   8  *
   9  * The author dedicates this file to the public domain.
  10  * You can do whatever you want with this file.
  11  */
  12
  13 #ifndef _WIMLIB_UNALIGNED_H
  14 #define _WIMLIB_UNALIGNED_H
  15
  16 #include "wimlib/compiler.h"
  17 #include "wimlib/endianness.h"
  18 #include "wimlib/types.h"
  19
  20 #define DEFINE_UNALIGNED_TYPE(type)                             \
  21 struct type##_unaligned {                                       \
  22         type v;                                                 \
  23 } _packed_attribute;                                            \
  24                                                                 \
  25 static inline type                                              \
  26 load_##type##_unaligned(const void *p)                          \
  27 {                                                               \
  28         return ((const struct type##_unaligned *)p)->v;         \
  29 }                                                               \
  30                                                                 \
  31 static inline void                                              \
  32 store_##type##_unaligned(type val, void *p)                     \
  33 {                                                               \
  34         ((struct type##_unaligned *)p)->v = val;                \
  35 }
  36
  37 DEFINE_UNALIGNED_TYPE(u16);
  38 DEFINE_UNALIGNED_TYPE(u32);
  39 DEFINE_UNALIGNED_TYPE(u64);
  40 DEFINE_UNALIGNED_TYPE(le16);
  41 DEFINE_UNALIGNED_TYPE(le32);
  42 DEFINE_UNALIGNED_TYPE(le64);
  43 DEFINE_UNALIGNED_TYPE(be16);
  44 DEFINE_UNALIGNED_TYPE(be32);
  45 DEFINE_UNALIGNED_TYPE(be64);
  46 DEFINE_UNALIGNED_TYPE(size_t);
  47 DEFINE_UNALIGNED_TYPE(machine_word_t);
  48
  49 #define load_word_unaligned     load_machine_word_t_unaligned
  50 #define store_word_unaligned    store_machine_word_t_unaligned
  51
  52 static inline u16
  53 get_unaligned_u16_le(const void *p)
  54 {
  55         u16 v;
  56
  57         if (UNALIGNED_ACCESS_IS_FAST) {
  58                 v = le16_to_cpu(load_le16_unaligned(p));
  59         } else {
  60                 const u8 *p8 = p;
  61                 v = 0;
  62                 v |= (u16)p8[0] << 0;
  63                 v |= (u16)p8[1] << 8;
  64         }
  65         return v;
  66 }
  67
  68 static inline u32
  69 get_unaligned_u32_le(const void *p)
  70 {
  71         u32 v;
  72
  73         if (UNALIGNED_ACCESS_IS_FAST) {
  74                 v = le32_to_cpu(load_le32_unaligned(p));
  75         } else {
  76                 const u8 *p8 = p;
  77                 v = 0;
  78                 v |= (u32)p8[0] << 0;
  79                 v |= (u32)p8[1] << 8;
  80                 v |= (u32)p8[2] << 16;
  81                 v |= (u32)p8[3] << 24;
  82         }
  83         return v;
  84 }
  85
  86 static inline void
  87 put_unaligned_u16_le(u16 v, void *p)
  88 {
  89         if (UNALIGNED_ACCESS_IS_FAST) {
  90                 store_le16_unaligned(cpu_to_le16(v), p);
  91         } else {
  92                 u8 *p8 = p;
  93                 p8[0] = (v >> 0) & 0xFF;
  94                 p8[1] = (v >> 8) & 0xFF;
  95         }
  96 }
  97
  98 static inline void
  99 put_unaligned_u32_le(u32 v, void *p)
 100 {
 101         if (UNALIGNED_ACCESS_IS_FAST) {
 102                 store_le32_unaligned(cpu_to_le32(v), p);
 103         } else {
 104                 u8 *p8 = p;
 105                 p8[0] = (v >> 0) & 0xFF;
 106                 p8[1] = (v >> 8) & 0xFF;
 107                 p8[2] = (v >> 16) & 0xFF;
 108                 p8[3] = (v >> 24) & 0xFF;
 109         }
 110 }
 111
 112 #endif /* _WIMLIB_UNALIGNED_H */