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) || defined(RISCV)
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