1 /*
   2  * Copyright (c) 2012, 2020, 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 SHARE_JFR_UTILITIES_JFRBIGENDIAN_HPP
  26 #define SHARE_JFR_UTILITIES_JFRBIGENDIAN_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/bytes.hpp"
  30 #include "utilities/macros.hpp"
  31 
  32 #ifndef VM_LITTLE_ENDIAN
  33 # define bigendian_16(x) (x)
  34 # define bigendian_32(x) (x)
  35 # define bigendian_64(x) (x)
  36 #else
  37 # define bigendian_16(x) Bytes::swap_u2(x)
  38 # define bigendian_32(x) Bytes::swap_u4(x)
  39 # define bigendian_64(x) Bytes::swap_u8(x)
  40 #endif
  41 
  42 class JfrBigEndian : AllStatic {
  43  private:
  44   template <typename T>
  45   static T read_bytes(const address location);
  46   template <typename T>
  47   static T read_unaligned(const address location);
  48  public:
  49   static bool platform_supports_unaligned_reads(void);
  50   static bool is_aligned(const void* location, size_t size);
  51   template <typename T>
  52   static T read(const void* location);
  53 };
  54 
  55 inline bool JfrBigEndian::is_aligned(const void* location, size_t size) {
  56   assert(size <= sizeof(u8), "just checking");
  57   if (size == sizeof(u1)) {
  58     return true;
  59   }
  60   // check address alignment for datum access
  61   return (((uintptr_t)location & (size -1)) == 0);
  62 }
  63 
  64 template <>
  65 inline u1 JfrBigEndian::read_bytes(const address location) {
  66   return (*location & 0xFF);
  67 }
  68 
  69 template <>
  70 inline u2 JfrBigEndian::read_bytes(const address location) {
  71   return Bytes::get_Java_u2(location);
  72 }
  73 
  74 template <>
  75 inline u4 JfrBigEndian::read_bytes(const address location) {
  76   return Bytes::get_Java_u4(location);
  77 }
  78 
  79 template <>
  80 inline u8 JfrBigEndian::read_bytes(const address location) {
  81   return Bytes::get_Java_u8(location);
  82 }
  83 
  84 template <typename T>
  85 inline T JfrBigEndian::read_unaligned(const address location) {
  86   assert(location != NULL, "just checking");
  87   switch (sizeof(T)) {
  88     case sizeof(u1) :
  89       return read_bytes<u1>(location);
  90     case sizeof(u2):
  91       return read_bytes<u2>(location);
  92     case sizeof(u4):
  93       return read_bytes<u4>(location);
  94     case sizeof(u8):
  95       return read_bytes<u8>(location);
  96     default:
  97       assert(false, "not reach");
  98   }
  99   return 0;
 100 }
 101 
 102 inline bool JfrBigEndian::platform_supports_unaligned_reads(void) {
 103 #if defined(IA32) || defined(AMD64) || defined(PPC) || defined(S390)
 104   return true;
 105 #elif defined(ARM) || defined(AARCH64)
 106   return false;
 107 #else
 108   #warning "Unconfigured platform"
 109   return false;
 110 #endif
 111 }
 112 
 113 template<typename T>
 114 inline T JfrBigEndian::read(const void* location) {
 115   assert(location != NULL, "just checking");
 116   assert(sizeof(T) <= sizeof(u8), "no support for arbitrary sizes");
 117   if (sizeof(T) == sizeof(u1)) {
 118     return *(T*)location;
 119   }
 120   if (is_aligned(location, sizeof(T)) || platform_supports_unaligned_reads()) {
 121     // fastest case
 122     switch (sizeof(T)) {
 123       case sizeof(u1):
 124         return *(T*)location;
 125       case sizeof(u2):
 126         return bigendian_16(*(T*)(location));
 127       case sizeof(u4):
 128         return bigendian_32(*(T*)(location));
 129       case sizeof(u8):
 130         return bigendian_64(*(T*)(location));
 131     }
 132   }
 133   return read_unaligned<T>((const address)location);
 134 }
 135 
 136 #endif // SHARE_JFR_UTILITIES_JFRBIGENDIAN_HPP