Java Unsafe.getUnsafe方法代码示例

import sun.misc.Unsafe; //导入方法依赖的package包/类
private static Unsafe initUnsafe() {
  try {
    return Unsafe.getUnsafe();
  } catch (SecurityException tryReflectionInstead) {
    try {
      return AccessController.doPrivileged(
          (PrivilegedExceptionAction<Unsafe>) () -> {
            Class<Unsafe> k = Unsafe.class;
            for (Field f : k.getDeclaredFields()) {
              f.setAccessible(true);
              Object x = f.get(null);
              if (k.isInstance(x)) {
                return k.cast(x);
              }
            }
            throw new NoSuchFieldError("the Unsafe");
          });
    } catch (PrivilegedActionException e) {
      throw new RuntimeException("Could not initialize intrinsics", e.getCause());
    }
  }
}
 

import sun.misc.Unsafe; //导入方法依赖的package包/类
/**
 * Loads this buffer's content into physical memory.
 *
 * <p> This method makes a best effort to ensure that, when it returns,
 * this buffer's content is resident in physical memory.  Invoking this
 * method may cause some number of page faults and I/O operations to
 * occur. </p>
 *
 * @return  This buffer
 */
public final MappedByteBuffer load() {
    checkMapped();
    if ((address == 0) || (capacity() == 0))
        return this;
    long offset = mappingOffset();
    long length = mappingLength(offset);
    load0(mappingAddress(offset), length);

    // Read a byte from each page to bring it into memory. A checksum
    // is computed as we go along to prevent the compiler from otherwise
    // considering the loop as dead code.
    Unsafe unsafe = Unsafe.getUnsafe();
    int ps = Bits.pageSize();
    int count = Bits.pageCount(length);
    long a = mappingAddress(offset);
    byte x = 0;
    for (int i=0; i<count; i++) {
        x ^= unsafe.getByte(a);
        a += ps;
    }
    if (unused != 0)
        unused = x;

    return this;
}
 

import sun.misc.Unsafe; //导入方法依赖的package包/类
private static Unsafe initUnsafe() {
    try {
        return Unsafe.getUnsafe();
    } catch (SecurityException se) {
        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            return (Unsafe) theUnsafe.get(Unsafe.class);
        } catch (Exception e) {
            throw new RuntimeException("exception while trying to get Unsafe", e);
        }
    }
}
 

import sun.misc.Unsafe; //导入方法依赖的package包/类
private static Unsafe initUnsafe() {
    try {
        // Fast path when we are trusted.
        return Unsafe.getUnsafe();
    } catch (SecurityException se) {
        // Slow path when we are not trusted.
        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            return (Unsafe) theUnsafe.get(Unsafe.class);
        } catch (Exception e) {
            throw new RuntimeException("exception while trying to get Unsafe", e);
        }
    }
}
 

import sun.misc.Unsafe; //导入方法依赖的package包/类
protected RenderBuffer(int numBytes) {
    unsafe = Unsafe.getUnsafe();
    curAddress = baseAddress = unsafe.allocateMemory(numBytes);
    endAddress = baseAddress + numBytes;
    capacity = numBytes;
}
 

import sun.misc.Unsafe; //导入方法依赖的package包/类
public void run() {
    Unsafe unsafe = Unsafe.getUnsafe();
}