30 lines
1.0 KiB
Java
30 lines
1.0 KiB
Java
import sun.misc.Unsafe;
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/**
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* Smallest possible Unsafe memory access: allocate 8 bytes off-heap, write a long, read it back, free it.
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* Run it under each value of --sun-misc-unsafe-memory-access to see what the JVM does.
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*/
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public class Probe {
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public static void main(String[] args) {
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Unsafe u = UnsafeAccess.get();
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System.out.println("got Unsafe instance");
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try {
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long addr = u.allocateMemory(8);
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u.putLong(addr, 42L);
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System.out.println("read back " + u.getLong(addr));
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u.freeMemory(addr);
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System.out.println("allocate/put/get/free all succeeded");
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} catch (Throwable t) {
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System.out.println("FAILED: " + t);
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}
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try {
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long addr2 = u.allocateMemory(8);
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u.putLong(addr2, 7L);
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System.out.println("second use read " + u.getLong(addr2));
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u.freeMemory(addr2);
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} catch (Throwable t) {
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System.out.println("second use FAILED: " + t);
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}
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}
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}
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