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December 10, 2015 13:08
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Unsafe-based sizeof
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| // A simpler method than reflection-based traversal, using Unsafe | |
| public static Unsafe getUnsafe() { | |
| Field f = Unsafe.class.getDeclaredField("theUnsafe"); | |
| f.setAccessible(true); | |
| return (Unsafe) f.get(null); | |
| } | |
| public static long sizeOf(Object o) { | |
| Unsafe u = getUnsafe(); | |
| HashSet<Field> fields = new HashSet<Field>(); | |
| Class c = o.getClass(); | |
| while (c != Object.class) { | |
| for (Field f : c.getDeclaredFields()) { | |
| if ((f.getModifiers() & Modifier.STATIC) == 0) { | |
| fields.add(f); | |
| } | |
| } | |
| c = c.getSuperclass(); | |
| } | |
| // get offset | |
| long maxSize = 0; | |
| for (Field f : fields) { | |
| long offset = u.objectFieldOffset(f); | |
| if (offset > maxSize) { | |
| maxSize = offset; | |
| } | |
| } | |
| return ((maxSize/8) + 1) * 8; // padding | |
| } |
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