1/*
2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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
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23 */
24
25#ifndef SHARE_VM_UTILITIES_SIZES_HPP
26#define SHARE_VM_UTILITIES_SIZES_HPP
27
28#include "memory/allocation.hpp"
29#include "utilities/globalDefinitions.hpp"
30
31// The following two classes are used to represent 'sizes' and 'offsets' in the VM;
32// they serve as 'unit' types. ByteSize is used for sizes measured in bytes, while
33// WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words
34// depending on platform).
35//
36// The classes are defined with friend functions operating on them instead of member
37// functions so that they (the classes) can be re-#define'd to int types in optimized
38// mode. This allows full type checking and maximum safety in debug mode, and full
39// optimizations (constant folding) and zero overhead (time and space wise) in the
40// optimized build (some compilers do not optimize one-element value classes but
41// instead create an object in memory - thus the overhead may be significant).
42//
43// Note: 1) DO NOT add new overloaded friend functions that do not have a unique function
44//          function name but require signature types for resolution. This will not work
45//          in optimized mode as both, ByteSize and WordSize are mapped to the same type
46//          and thus the distinction would not be possible anymore (=> compiler errors).
47//
48//       2) DO NOT add non-static member functions as they cannot be mapped so something
49//          compilable in the optimized build. Static member functions could be added
50//          but require a corresponding class definition in the optimized build.
51//
52// These classes should help doing a transition from (currently) word-size based offsets
53// to byte-size based offsets in the VM (this will be important if we desire to pack
54// objects more densely in the VM for 64bit machines). Such a transition should proceed
55// in two steps to minimize the risk of introducing hard-to-find bugs:
56//
57// a) first transition the whole VM into a form where all sizes are strongly typed
58// b) change all WordSize's to ByteSize's where desired and fix the compilation errors
59
60
61#ifdef ASSERT
62
63class ByteSize VALUE_OBJ_CLASS_SPEC {
64 private:
65  int _size;
66
67  // Note: This constructor must be private to avoid implicit conversions!
68  ByteSize(int size)                                  { _size = size; }
69
70 public:
71  // constructors
72  inline friend ByteSize in_ByteSize(int size);
73
74  // accessors
75  inline friend int in_bytes(ByteSize x);
76
77  // operators
78  friend ByteSize operator + (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) + in_bytes(y)); }
79  friend ByteSize operator - (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) - in_bytes(y)); }
80  friend ByteSize operator * (ByteSize x, int      y) { return ByteSize(in_bytes(x) * y          ); }
81
82  // comparison
83  friend bool operator == (ByteSize x, ByteSize y)    { return in_bytes(x) == in_bytes(y); }
84  friend bool operator != (ByteSize x, ByteSize y)    { return in_bytes(x) != in_bytes(y); }
85  friend bool operator <  (ByteSize x, ByteSize y)    { return in_bytes(x) <  in_bytes(y); }
86  friend bool operator <= (ByteSize x, ByteSize y)    { return in_bytes(x) <= in_bytes(y); }
87  friend bool operator >  (ByteSize x, ByteSize y)    { return in_bytes(x) >  in_bytes(y); }
88  friend bool operator >= (ByteSize x, ByteSize y)    { return in_bytes(x) >= in_bytes(y); }
89};
90
91inline ByteSize in_ByteSize(int size) { return ByteSize(size); }
92inline int      in_bytes(ByteSize x)  { return x._size; }
93
94
95class WordSize VALUE_OBJ_CLASS_SPEC {
96 private:
97  int _size;
98
99  // Note: This constructor must be private to avoid implicit conversions!
100  WordSize(int size)                                  { _size = size; }
101
102 public:
103  // constructors
104  inline friend WordSize in_WordSize(int size);
105
106  // accessors
107  inline friend int in_words(WordSize x);
108
109  // operators
110  friend WordSize operator + (WordSize x, WordSize y) { return WordSize(in_words(x) + in_words(y)); }
111  friend WordSize operator - (WordSize x, WordSize y) { return WordSize(in_words(x) - in_words(y)); }
112  friend WordSize operator * (WordSize x, int      y) { return WordSize(in_words(x) * y          ); }
113
114  // comparison
115  friend bool operator == (WordSize x, WordSize y)    { return in_words(x) == in_words(y); }
116  friend bool operator != (WordSize x, WordSize y)    { return in_words(x) != in_words(y); }
117  friend bool operator <  (WordSize x, WordSize y)    { return in_words(x) <  in_words(y); }
118  friend bool operator <= (WordSize x, WordSize y)    { return in_words(x) <= in_words(y); }
119  friend bool operator >  (WordSize x, WordSize y)    { return in_words(x) >  in_words(y); }
120  friend bool operator >= (WordSize x, WordSize y)    { return in_words(x) >= in_words(y); }
121};
122
123inline WordSize in_WordSize(int size) { return WordSize(size); }
124inline int      in_words(WordSize x)  { return x._size; }
125
126
127#else // ASSERT
128
129// The following definitions must match the corresponding friend declarations
130// in the Byte/WordSize classes if they are typedef'ed to be int. This will
131// be the case in optimized mode to ensure zero overhead for these types.
132//
133// Note: If a compiler does not inline these function calls away, one may
134//       want to use #define's to make sure full optimization (constant
135//       folding in particular) is possible.
136
137typedef int ByteSize;
138inline ByteSize in_ByteSize(int size)                 { return size; }
139inline int      in_bytes   (ByteSize x)               { return x; }
140
141typedef int WordSize;
142inline WordSize in_WordSize(int size)                 { return size; }
143inline int      in_words   (WordSize x)               { return x; }
144
145#endif // ASSERT
146
147
148// Use the following #define to get C++ field member offsets
149
150#define byte_offset_of(klass,field)   in_ByteSize((int)offset_of(klass, field))
151
152#endif // SHARE_VM_UTILITIES_SIZES_HPP
153