Brian Carlstrom | 2cf03dc | 2013-05-22 11:05:31 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2007 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package sun.misc; |
| 18 | |
| 19 | import dalvik.system.VMStack; |
| 20 | import java.lang.reflect.Field; |
| 21 | import java.lang.reflect.Modifier; |
| 22 | |
| 23 | /** |
| 24 | * The package name notwithstanding, this class is the quasi-standard |
| 25 | * way for Java code to gain access to and use functionality which, |
| 26 | * when unsupervised, would allow one to break the pointer/type safety |
| 27 | * of Java. |
| 28 | */ |
| 29 | public final class Unsafe { |
| 30 | /** Traditional dalvik name. */ |
| 31 | private static final Unsafe THE_ONE = new Unsafe(); |
| 32 | /** Traditional RI name. */ |
| 33 | private static final Unsafe theUnsafe = THE_ONE; |
| 34 | |
| 35 | /** |
| 36 | * This class is only privately instantiable. |
| 37 | */ |
| 38 | private Unsafe() {} |
| 39 | |
| 40 | /** |
| 41 | * Gets the unique instance of this class. This is only allowed in |
| 42 | * very limited situations. |
| 43 | */ |
| 44 | public static Unsafe getUnsafe() { |
| 45 | /* |
| 46 | * Only code on the bootclasspath is allowed to get at the |
| 47 | * Unsafe instance. |
| 48 | */ |
| 49 | ClassLoader calling = VMStack.getCallingClassLoader(); |
| 50 | if ((calling != null) && (calling != Unsafe.class.getClassLoader())) { |
| 51 | throw new SecurityException("Unsafe access denied"); |
| 52 | } |
| 53 | |
| 54 | return THE_ONE; |
| 55 | } |
| 56 | |
| 57 | /** |
| 58 | * Gets the raw byte offset from the start of an object's memory to |
| 59 | * the memory used to store the indicated instance field. |
| 60 | * |
| 61 | * @param field non-null; the field in question, which must be an |
| 62 | * instance field |
| 63 | * @return the offset to the field |
| 64 | */ |
| 65 | public long objectFieldOffset(Field field) { |
| 66 | if (Modifier.isStatic(field.getModifiers())) { |
| 67 | throw new IllegalArgumentException("valid for instance fields only"); |
| 68 | } |
| 69 | return field.getOffset(); |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Gets the offset from the start of an array object's memory to |
| 74 | * the memory used to store its initial (zeroeth) element. |
| 75 | * |
| 76 | * @param clazz non-null; class in question; must be an array class |
| 77 | * @return the offset to the initial element |
| 78 | */ |
| 79 | public int arrayBaseOffset(Class clazz) { |
| 80 | Class<?> component = clazz.getComponentType(); |
| 81 | if (component == null) { |
| 82 | throw new IllegalArgumentException("Valid for array classes only: " + clazz); |
| 83 | } |
Hiroshi Yamauchi | 7ce6ae5 | 2014-02-11 11:46:18 -0800 | [diff] [blame] | 84 | return getArrayBaseOffsetForComponentType(component); |
Brian Carlstrom | 2cf03dc | 2013-05-22 11:05:31 -0700 | [diff] [blame] | 85 | } |
| 86 | |
| 87 | /** |
| 88 | * Gets the size of each element of the given array class. |
| 89 | * |
| 90 | * @param clazz non-null; class in question; must be an array class |
| 91 | * @return > 0; the size of each element of the array |
| 92 | */ |
| 93 | public int arrayIndexScale(Class clazz) { |
| 94 | Class<?> component = clazz.getComponentType(); |
| 95 | if (component == null) { |
| 96 | throw new IllegalArgumentException("Valid for array classes only: " + clazz); |
| 97 | } |
Hiroshi Yamauchi | 7ce6ae5 | 2014-02-11 11:46:18 -0800 | [diff] [blame] | 98 | return getArrayIndexScaleForComponentType(component); |
Brian Carlstrom | 2cf03dc | 2013-05-22 11:05:31 -0700 | [diff] [blame] | 99 | } |
| 100 | |
Hiroshi Yamauchi | 7ce6ae5 | 2014-02-11 11:46:18 -0800 | [diff] [blame] | 101 | private static native int getArrayBaseOffsetForComponentType(Class component_class); |
| 102 | private static native int getArrayIndexScaleForComponentType(Class component_class); |
| 103 | |
Brian Carlstrom | 2cf03dc | 2013-05-22 11:05:31 -0700 | [diff] [blame] | 104 | /** |
| 105 | * Performs a compare-and-set operation on an <code>int</code> |
| 106 | * field within the given object. |
| 107 | * |
| 108 | * @param obj non-null; object containing the field |
| 109 | * @param offset offset to the field within <code>obj</code> |
| 110 | * @param expectedValue expected value of the field |
| 111 | * @param newValue new value to store in the field if the contents are |
| 112 | * as expected |
| 113 | * @return <code>true</code> if the new value was in fact stored, and |
| 114 | * <code>false</code> if not |
| 115 | */ |
| 116 | public native boolean compareAndSwapInt(Object obj, long offset, |
| 117 | int expectedValue, int newValue); |
| 118 | |
| 119 | /** |
| 120 | * Performs a compare-and-set operation on a <code>long</code> |
| 121 | * field within the given object. |
| 122 | * |
| 123 | * @param obj non-null; object containing the field |
| 124 | * @param offset offset to the field within <code>obj</code> |
| 125 | * @param expectedValue expected value of the field |
| 126 | * @param newValue new value to store in the field if the contents are |
| 127 | * as expected |
| 128 | * @return <code>true</code> if the new value was in fact stored, and |
| 129 | * <code>false</code> if not |
| 130 | */ |
| 131 | public native boolean compareAndSwapLong(Object obj, long offset, |
| 132 | long expectedValue, long newValue); |
| 133 | |
| 134 | /** |
| 135 | * Performs a compare-and-set operation on an <code>Object</code> |
| 136 | * field (that is, a reference field) within the given object. |
| 137 | * |
| 138 | * @param obj non-null; object containing the field |
| 139 | * @param offset offset to the field within <code>obj</code> |
| 140 | * @param expectedValue expected value of the field |
| 141 | * @param newValue new value to store in the field if the contents are |
| 142 | * as expected |
| 143 | * @return <code>true</code> if the new value was in fact stored, and |
| 144 | * <code>false</code> if not |
| 145 | */ |
| 146 | public native boolean compareAndSwapObject(Object obj, long offset, |
| 147 | Object expectedValue, Object newValue); |
| 148 | |
| 149 | /** |
| 150 | * Gets an <code>int</code> field from the given object, |
| 151 | * using <code>volatile</code> semantics. |
| 152 | * |
| 153 | * @param obj non-null; object containing the field |
| 154 | * @param offset offset to the field within <code>obj</code> |
| 155 | * @return the retrieved value |
| 156 | */ |
| 157 | public native int getIntVolatile(Object obj, long offset); |
| 158 | |
| 159 | /** |
| 160 | * Stores an <code>int</code> field into the given object, |
| 161 | * using <code>volatile</code> semantics. |
| 162 | * |
| 163 | * @param obj non-null; object containing the field |
| 164 | * @param offset offset to the field within <code>obj</code> |
| 165 | * @param newValue the value to store |
| 166 | */ |
| 167 | public native void putIntVolatile(Object obj, long offset, int newValue); |
| 168 | |
| 169 | /** |
| 170 | * Gets a <code>long</code> field from the given object, |
| 171 | * using <code>volatile</code> semantics. |
| 172 | * |
| 173 | * @param obj non-null; object containing the field |
| 174 | * @param offset offset to the field within <code>obj</code> |
| 175 | * @return the retrieved value |
| 176 | */ |
| 177 | public native long getLongVolatile(Object obj, long offset); |
| 178 | |
| 179 | /** |
| 180 | * Stores a <code>long</code> field into the given object, |
| 181 | * using <code>volatile</code> semantics. |
| 182 | * |
| 183 | * @param obj non-null; object containing the field |
| 184 | * @param offset offset to the field within <code>obj</code> |
| 185 | * @param newValue the value to store |
| 186 | */ |
| 187 | public native void putLongVolatile(Object obj, long offset, long newValue); |
| 188 | |
| 189 | /** |
| 190 | * Gets an <code>Object</code> field from the given object, |
| 191 | * using <code>volatile</code> semantics. |
| 192 | * |
| 193 | * @param obj non-null; object containing the field |
| 194 | * @param offset offset to the field within <code>obj</code> |
| 195 | * @return the retrieved value |
| 196 | */ |
| 197 | public native Object getObjectVolatile(Object obj, long offset); |
| 198 | |
| 199 | /** |
| 200 | * Stores an <code>Object</code> field into the given object, |
| 201 | * using <code>volatile</code> semantics. |
| 202 | * |
| 203 | * @param obj non-null; object containing the field |
| 204 | * @param offset offset to the field within <code>obj</code> |
| 205 | * @param newValue the value to store |
| 206 | */ |
| 207 | public native void putObjectVolatile(Object obj, long offset, |
| 208 | Object newValue); |
| 209 | |
| 210 | /** |
| 211 | * Gets an <code>int</code> field from the given object. |
| 212 | * |
| 213 | * @param obj non-null; object containing the field |
| 214 | * @param offset offset to the field within <code>obj</code> |
| 215 | * @return the retrieved value |
| 216 | */ |
| 217 | public native int getInt(Object obj, long offset); |
| 218 | |
| 219 | /** |
| 220 | * Stores an <code>int</code> field into the given object. |
| 221 | * |
| 222 | * @param obj non-null; object containing the field |
| 223 | * @param offset offset to the field within <code>obj</code> |
| 224 | * @param newValue the value to store |
| 225 | */ |
| 226 | public native void putInt(Object obj, long offset, int newValue); |
| 227 | |
| 228 | /** |
| 229 | * Lazy set an int field. |
| 230 | */ |
| 231 | public native void putOrderedInt(Object obj, long offset, int newValue); |
| 232 | |
| 233 | /** |
| 234 | * Gets a <code>long</code> field from the given object. |
| 235 | * |
| 236 | * @param obj non-null; object containing the field |
| 237 | * @param offset offset to the field within <code>obj</code> |
| 238 | * @return the retrieved value |
| 239 | */ |
| 240 | public native long getLong(Object obj, long offset); |
| 241 | |
| 242 | /** |
| 243 | * Stores a <code>long</code> field into the given object. |
| 244 | * |
| 245 | * @param obj non-null; object containing the field |
| 246 | * @param offset offset to the field within <code>obj</code> |
| 247 | * @param newValue the value to store |
| 248 | */ |
| 249 | public native void putLong(Object obj, long offset, long newValue); |
| 250 | |
| 251 | /** |
| 252 | * Lazy set a long field. |
| 253 | */ |
| 254 | public native void putOrderedLong(Object obj, long offset, long newValue); |
| 255 | |
| 256 | /** |
| 257 | * Gets an <code>Object</code> field from the given object. |
| 258 | * |
| 259 | * @param obj non-null; object containing the field |
| 260 | * @param offset offset to the field within <code>obj</code> |
| 261 | * @return the retrieved value |
| 262 | */ |
| 263 | public native Object getObject(Object obj, long offset); |
| 264 | |
| 265 | /** |
| 266 | * Stores an <code>Object</code> field into the given object. |
| 267 | * |
| 268 | * @param obj non-null; object containing the field |
| 269 | * @param offset offset to the field within <code>obj</code> |
| 270 | * @param newValue the value to store |
| 271 | */ |
| 272 | public native void putObject(Object obj, long offset, Object newValue); |
| 273 | |
| 274 | /** |
| 275 | * Lazy set an object field. |
| 276 | */ |
| 277 | public native void putOrderedObject(Object obj, long offset, |
| 278 | Object newValue); |
| 279 | |
| 280 | /** |
| 281 | * Parks the calling thread for the specified amount of time, |
| 282 | * unless the "permit" for the thread is already available (due to |
| 283 | * a previous call to {@link #unpark}. This method may also return |
| 284 | * spuriously (that is, without the thread being told to unpark |
| 285 | * and without the indicated amount of time elapsing). |
| 286 | * |
| 287 | * <p>See {@link java.util.concurrent.locks.LockSupport} for more |
| 288 | * in-depth information of the behavior of this method.</p> |
| 289 | * |
| 290 | * @param absolute whether the given time value is absolute |
| 291 | * milliseconds-since-the-epoch (<code>true</code>) or relative |
| 292 | * nanoseconds-from-now (<code>false</code>) |
| 293 | * @param time the (absolute millis or relative nanos) time value |
| 294 | */ |
| 295 | public void park(boolean absolute, long time) { |
| 296 | if (absolute) { |
| 297 | Thread.currentThread().parkUntil(time); |
| 298 | } else { |
| 299 | Thread.currentThread().parkFor(time); |
| 300 | } |
| 301 | } |
| 302 | |
| 303 | /** |
| 304 | * Unparks the given object, which must be a {@link Thread}. |
| 305 | * |
| 306 | * <p>See {@link java.util.concurrent.locks.LockSupport} for more |
| 307 | * in-depth information of the behavior of this method.</p> |
| 308 | * |
| 309 | * @param obj non-null; the object to unpark |
| 310 | */ |
| 311 | public void unpark(Object obj) { |
| 312 | if (obj instanceof Thread) { |
| 313 | ((Thread) obj).unpark(); |
| 314 | } else { |
| 315 | throw new IllegalArgumentException("valid for Threads only"); |
| 316 | } |
| 317 | } |
| 318 | |
| 319 | /** |
| 320 | * Allocates an instance of the given class without running the constructor. |
| 321 | * The class' <clinit> will be run, if necessary. |
| 322 | */ |
| 323 | public native Object allocateInstance(Class<?> c); |
| 324 | } |