1 /*
   2  * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef CPU_X86_VM_BYTES_X86_HPP
  26 #define CPU_X86_VM_BYTES_X86_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/macros.hpp"
  30 
  31 class Bytes: AllStatic {
  32  private:
  33 #ifndef AMD64
  34   // Helper function for swap_u8
  35   static inline u8   swap_u8_base(u4 x, u4 y);        // compiler-dependent implementation
  36 #endif // AMD64
  37 
  38  public:
  39   // Efficient reading and writing of unaligned unsigned data in platform-specific byte ordering
  40   template <typename T>
  41   static inline T get_native(const void* p) {
  42     assert(p != NULL, "null pointer");
  43 
  44     T x;
  45 
  46     if (is_ptr_aligned(p, sizeof(T))) {
  47       x = *(T*)p;
  48     } else {
  49       memcpy(&x, p, sizeof(T));
  50     }
  51 
  52     return x;
  53   }
  54 
  55   template <typename T>
  56   static inline void put_native(void* p, T x) {
  57     assert(p != NULL, "null pointer");
  58 
  59     if (is_ptr_aligned(p, sizeof(T))) {
  60       *(T*)p = x;
  61     } else {
  62       memcpy(p, &x, sizeof(T));
  63     }
  64   }
  65 
  66   static inline u2   get_native_u2(address p)         { return get_native<u2>((void*)p); }
  67   static inline u4   get_native_u4(address p)         { return get_native<u4>((void*)p); }
  68   static inline u8   get_native_u8(address p)         { return get_native<u8>((void*)p); }
  69   static inline void put_native_u2(address p, u2 x)   { put_native<u2>((void*)p, x); }
  70   static inline void put_native_u4(address p, u4 x)   { put_native<u4>((void*)p, x); }
  71   static inline void put_native_u8(address p, u8 x)   { put_native<u8>((void*)p, x); }
  72 
  73   // Efficient reading and writing of unaligned unsigned data in Java
  74   // byte ordering (i.e. big-endian ordering). Byte-order reversal is
  75   // needed since x86 CPUs use little-endian format.
  76   template <typename T>
  77   static inline T get_Java(const address p) {
  78     T x = get_native<T>(p);
  79 
  80     if (Endian::is_Java_byte_ordering_different()) {
  81       x = swap<T>(x);
  82     }
  83 
  84     return x;
  85   }
  86 
  87   template <typename T>
  88   static inline void put_Java(address p, T x) {
  89     if (Endian::is_Java_byte_ordering_different()) {
  90       x = swap<T>(x);
  91     }
  92 
  93     put_native<T>(p, x);
  94   }
  95 
  96   static inline u2   get_Java_u2(address p)           { return get_Java<u2>(p); }
  97   static inline u4   get_Java_u4(address p)           { return get_Java<u4>(p); }
  98   static inline u8   get_Java_u8(address p)           { return get_Java<u8>(p); }
  99 
 100   static inline void put_Java_u2(address p, u2 x)     { put_Java<u2>(p, x); }
 101   static inline void put_Java_u4(address p, u4 x)     { put_Java<u4>(p, x); }
 102   static inline void put_Java_u8(address p, u8 x)     { put_Java<u8>(p, x); }
 103 
 104   // Efficient swapping of byte ordering
 105   template <typename T>
 106   static T swap(T x) {
 107     switch (sizeof(T)) {
 108     case sizeof(u1): return x;
 109     case sizeof(u2): return swap_u2(x);
 110     case sizeof(u4): return swap_u4(x);
 111     case sizeof(u8): return swap_u8(x);
 112     default:
 113       guarantee(false, "invalid size: " SIZE_FORMAT "\n", sizeof(T));
 114       return 0;
 115     }
 116   }
 117 
 118   static inline u2   swap_u2(u2 x);                   // compiler-dependent implementation
 119   static inline u4   swap_u4(u4 x);                   // compiler-dependent implementation
 120   static inline u8   swap_u8(u8 x);
 121 };
 122 
 123 // The following header contains the implementations of swap_u2, swap_u4, and swap_u8[_base]
 124 #include OS_CPU_HEADER_INLINE(bytes)
 125 
 126 #endif // CPU_X86_VM_BYTES_X86_HPP