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1 /*
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2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 //------------------------------------------------------------------------------------------------------------------------
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26 // In order to preserve oops during garbage collection, they should be
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27 // allocated and passed around via Handles within the VM. A handle is
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28 // simply an extra indirection allocated in a thread local handle area.
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29 //
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30 // A handle is a ValueObj, so it can be passed around as a value, can
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31 // be used as a parameter w/o using &-passing, and can be returned as a
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32 // return value.
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33 //
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34 // oop parameters and return types should be Handles whenever feasible.
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35 //
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36 // Handles are declared in a straight-forward manner, e.g.
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37 //
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38 // oop obj = ...;
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39 // Handle h1(obj); // allocate new handle
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40 // Handle h2(thread, obj); // faster allocation when current thread is known
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41 // Handle h3; // declare handle only, no allocation occurs
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42 // ...
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43 // h3 = h1; // make h3 refer to same indirection as h1
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44 // oop obj2 = h2(); // get handle value
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45 // h1->print(); // invoking operation on oop
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46 //
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47 // Handles are specialized for different oop types to provide extra type
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48 // information and avoid unnecessary casting. For each oop type xxxOop
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49 // there is a corresponding handle called xxxHandle, e.g.
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50 //
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51 // oop Handle
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52 // methodOop methodHandle
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53 // instanceOop instanceHandle
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54 //
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55 // For klassOops, it is often useful to model the Klass hierarchy in order
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56 // to get access to the klass_part without casting. For each xxxKlass there
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57 // is a corresponding handle called xxxKlassHandle, e.g.
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58 //
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59 // klassOop Klass KlassHandle
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60 // klassOop methodKlass methodKlassHandle
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61 // klassOop instanceKlass instanceKlassHandle
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62 //
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63
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64 //------------------------------------------------------------------------------------------------------------------------
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65 // Base class for all handles. Provides overloading of frequently
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66 // used operators for ease of use.
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67
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68 class Handle VALUE_OBJ_CLASS_SPEC {
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69 private:
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70 oop* _handle;
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71
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72 protected:
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73 oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; }
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74 oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; }
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75
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76 public:
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77 // Constructors
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78 Handle() { _handle = NULL; }
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79 Handle(oop obj);
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80 #ifndef ASSERT
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81 Handle(Thread* thread, oop obj);
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82 #else
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83 // Don't inline body with assert for current thread
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84 Handle(Thread* thread, oop obj);
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85 #endif // ASSERT
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86
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87 // General access
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88 oop operator () () const { return obj(); }
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89 oop operator -> () const { return non_null_obj(); }
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90 bool operator == (oop o) const { return obj() == o; }
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91 bool operator == (const Handle& h) const { return obj() == h.obj(); }
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92
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93 // Null checks
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94 bool is_null() const { return _handle == NULL; }
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95 bool not_null() const { return _handle != NULL; }
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96
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97 // Debugging
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98 void print() { obj()->print(); }
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99
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100 // Direct interface, use very sparingly.
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101 // Used by JavaCalls to quickly convert handles and to create handles static data structures.
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102 // Constructor takes a dummy argument to prevent unintentional type conversion in C++.
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103 Handle(oop *handle, bool dummy) { _handle = handle; }
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104
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105 // Raw handle access. Allows easy duplication of Handles. This can be very unsafe
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106 // since duplicates is only valid as long as original handle is alive.
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107 oop* raw_value() { return _handle; }
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108 static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; }
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109 };
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110
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111
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112 //------------------------------------------------------------------------------------------------------------------------
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113 // Base class for Handles containing klassOops. Provides overloading of frequently
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114 // used operators for ease of use and typed access to the Klass part.
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115 class KlassHandle: public Handle {
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116 protected:
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117 klassOop obj() const { return (klassOop)Handle::obj(); }
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118 klassOop non_null_obj() const { return (klassOop)Handle::non_null_obj(); }
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119 Klass* as_klass() const { return non_null_obj()->klass_part(); }
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120
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121 public:
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122 // Constructors
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123 KlassHandle () : Handle() {}
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124 KlassHandle (oop obj) : Handle(obj) {
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125 assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop");
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126 }
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127 KlassHandle (Klass* kl) : Handle(kl ? kl->as_klassOop() : (klassOop)NULL) {
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128 assert(SharedSkipVerify || is_null() || obj()->is_klass(), "not a klassOop");
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129 }
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130
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131 // Faster versions passing Thread
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132 KlassHandle (Thread* thread, oop obj) : Handle(thread, obj) {
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133 assert(SharedSkipVerify || is_null() || obj->is_klass(), "not a klassOop");
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134 }
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135 KlassHandle (Thread *thread, Klass* kl)
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136 : Handle(thread, kl ? kl->as_klassOop() : (klassOop)NULL) {
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137 assert(is_null() || obj()->is_klass(), "not a klassOop");
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138 }
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139
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140 // General access
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141 klassOop operator () () const { return obj(); }
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142 Klass* operator -> () const { return as_klass(); }
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143 };
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144
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145
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146 //------------------------------------------------------------------------------------------------------------------------
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147 // Specific Handles for different oop types
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148 #define DEF_HANDLE(type, is_a) \
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149 class type##Handle; \
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150 class type##Handle: public Handle { \
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151 protected: \
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152 type##Oop obj() const { return (type##Oop)Handle::obj(); } \
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153 type##Oop non_null_obj() const { return (type##Oop)Handle::non_null_obj(); } \
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154 \
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155 public: \
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156 /* Constructors */ \
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157 type##Handle () : Handle() {} \
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158 type##Handle (type##Oop obj) : Handle((oop)obj) { \
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159 assert(SharedSkipVerify || is_null() || ((oop)obj)->is_a(), \
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160 "illegal type"); \
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161 } \
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162 type##Handle (Thread* thread, type##Oop obj) : Handle(thread, (oop)obj) { \
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163 assert(SharedSkipVerify || is_null() || ((oop)obj)->is_a(), "illegal type"); \
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164 } \
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165 \
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166 /* Special constructor, use sparingly */ \
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167 type##Handle (type##Oop *handle, bool dummy) : Handle((oop*)handle, dummy) {} \
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168 \
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169 /* Operators for ease of use */ \
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170 type##Oop operator () () const { return obj(); } \
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171 type##Oop operator -> () const { return non_null_obj(); } \
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172 };
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173
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174
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175 DEF_HANDLE(instance , is_instance )
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176 DEF_HANDLE(method , is_method )
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177 DEF_HANDLE(constMethod , is_constMethod )
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178 DEF_HANDLE(methodData , is_methodData )
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179 DEF_HANDLE(array , is_array )
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180 DEF_HANDLE(constantPool , is_constantPool )
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181 DEF_HANDLE(constantPoolCache, is_constantPoolCache)
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182 DEF_HANDLE(objArray , is_objArray )
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183 DEF_HANDLE(typeArray , is_typeArray )
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184 DEF_HANDLE(symbol , is_symbol )
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185
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186 //------------------------------------------------------------------------------------------------------------------------
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187 // Specific KlassHandles for different Klass types
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188
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189 #define DEF_KLASS_HANDLE(type, is_a) \
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190 class type##Handle : public KlassHandle { \
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191 public: \
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192 /* Constructors */ \
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193 type##Handle () : KlassHandle() {} \
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194 type##Handle (klassOop obj) : KlassHandle(obj) { \
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195 assert(SharedSkipVerify || is_null() || obj->klass_part()->is_a(), \
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196 "illegal type"); \
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197 } \
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198 type##Handle (Thread* thread, klassOop obj) : KlassHandle(thread, obj) { \
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199 assert(SharedSkipVerify || is_null() || obj->klass_part()->is_a(), \
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200 "illegal type"); \
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201 } \
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202 \
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203 /* Access to klass part */ \
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204 type* operator -> () const { return (type*)obj()->klass_part(); } \
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205 \
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206 static type##Handle cast(KlassHandle h) { return type##Handle(h()); } \
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207 \
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208 };
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209
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210
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211 DEF_KLASS_HANDLE(instanceKlass , oop_is_instance_slow )
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212 DEF_KLASS_HANDLE(methodKlass , oop_is_method )
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213 DEF_KLASS_HANDLE(constMethodKlass , oop_is_constMethod )
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214 DEF_KLASS_HANDLE(klassKlass , oop_is_klass )
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215 DEF_KLASS_HANDLE(arrayKlassKlass , oop_is_arrayKlass )
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216 DEF_KLASS_HANDLE(objArrayKlassKlass , oop_is_objArrayKlass )
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217 DEF_KLASS_HANDLE(typeArrayKlassKlass , oop_is_typeArrayKlass)
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218 DEF_KLASS_HANDLE(arrayKlass , oop_is_array )
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219 DEF_KLASS_HANDLE(typeArrayKlass , oop_is_typeArray_slow)
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220 DEF_KLASS_HANDLE(objArrayKlass , oop_is_objArray_slow )
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221 DEF_KLASS_HANDLE(symbolKlass , oop_is_symbol )
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222 DEF_KLASS_HANDLE(constantPoolKlass , oop_is_constantPool )
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223 DEF_KLASS_HANDLE(constantPoolCacheKlass, oop_is_constantPool )
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224
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225
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226 //------------------------------------------------------------------------------------------------------------------------
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227 // Thread local handle area
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228
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229 class HandleArea: public Arena {
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230 friend class HandleMark;
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231 friend class NoHandleMark;
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232 friend class ResetNoHandleMark;
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233 #ifdef ASSERT
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234 int _handle_mark_nesting;
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235 int _no_handle_mark_nesting;
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236 #endif
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237 HandleArea* _prev; // link to outer (older) area
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238 public:
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239 // Constructor
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240 HandleArea(HandleArea* prev) {
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241 debug_only(_handle_mark_nesting = 0);
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242 debug_only(_no_handle_mark_nesting = 0);
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243 _prev = prev;
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244 }
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245
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246 // Handle allocation
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247 private:
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248 oop* real_allocate_handle(oop obj) {
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249 #ifdef ASSERT
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250 oop* handle = (oop*) (UseMallocOnly ? internal_malloc_4(oopSize) : Amalloc_4(oopSize));
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251 #else
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252 oop* handle = (oop*) Amalloc_4(oopSize);
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253 #endif
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254 *handle = obj;
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255 return handle;
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256 }
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257 public:
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258 #ifdef ASSERT
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259 oop* allocate_handle(oop obj);
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260 #else
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261 oop* allocate_handle(oop obj) { return real_allocate_handle(obj); }
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262 #endif
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263
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264 // Garbage collection support
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265 void oops_do(OopClosure* f);
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266
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267 // Number of handles in use
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268 size_t used() const { return Arena::used() / oopSize; }
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269
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270 debug_only(bool no_handle_mark_active() { return _no_handle_mark_nesting > 0; })
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271 };
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272
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273
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274 //------------------------------------------------------------------------------------------------------------------------
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275 // Handles are allocated in a (growable) thread local handle area. Deallocation
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276 // is managed using a HandleMark. It should normally not be necessary to use
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277 // HandleMarks manually.
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278 //
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279 // A HandleMark constructor will record the current handle area top, and the
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280 // desctructor will reset the top, destroying all handles allocated in between.
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281 // The following code will therefore NOT work:
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282 //
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283 // Handle h;
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284 // {
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285 // HandleMark hm;
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286 // h = Handle(obj);
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287 // }
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288 // h()->print(); // WRONG, h destroyed by HandleMark destructor.
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289 //
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290 // If h has to be preserved, it can be converted to an oop or a local JNI handle
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291 // across the HandleMark boundary.
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292
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293 // The base class of HandleMark should have been StackObj but we also heap allocate
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294 // a HandleMark when a thread is created.
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295
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296 class HandleMark {
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297 private:
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298 Thread *_thread; // thread that owns this mark
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299 HandleArea *_area; // saved handle area
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300 Chunk *_chunk; // saved arena chunk
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301 char *_hwm, *_max; // saved arena info
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302 NOT_PRODUCT(size_t _size_in_bytes;) // size of handle area
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303 // Link to previous active HandleMark in thread
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304 HandleMark* _previous_handle_mark;
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305
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306 void initialize(Thread* thread); // common code for constructors
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307 void set_previous_handle_mark(HandleMark* mark) { _previous_handle_mark = mark; }
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308 HandleMark* previous_handle_mark() const { return _previous_handle_mark; }
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309
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310 public:
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311 HandleMark(); // see handles_inline.hpp
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312 HandleMark(Thread* thread) { initialize(thread); }
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313 ~HandleMark();
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314
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315 // Functions used by HandleMarkCleaner
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316 // called in the constructor of HandleMarkCleaner
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317 void push();
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318 // called in the destructor of HandleMarkCleaner
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319 void pop_and_restore();
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320 };
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321
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322 //------------------------------------------------------------------------------------------------------------------------
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323 // A NoHandleMark stack object will verify that no handles are allocated
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324 // in its scope. Enabled in debug mode only.
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325
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326 class NoHandleMark: public StackObj {
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327 public:
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328 #ifdef ASSERT
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329 NoHandleMark();
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330 ~NoHandleMark();
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331 #else
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332 NoHandleMark() {}
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333 ~NoHandleMark() {}
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334 #endif
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335 };
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336
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337
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338 class ResetNoHandleMark: public StackObj {
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339 int _no_handle_mark_nesting;
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340 public:
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341 #ifdef ASSERT
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342 ResetNoHandleMark();
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343 ~ResetNoHandleMark();
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344 #else
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345 ResetNoHandleMark() {}
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346 ~ResetNoHandleMark() {}
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347 #endif
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348 };
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