1 /*
  2  * Copyright (c) 2012, 2022, 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/allStatic.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
--- EOF ---