[GitHub] [flink] tillrohrmann commented on a change in pull request #11160: [FLINK-15094] Use Unsafe to instantiate and construct DirectByteBuffer

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tillrohrmann commented on a change in pull request #11160: [FLINK-15094] Use Unsafe to instantiate and construct DirectByteBuffer
URL: https://github.com/apache/flink/pull/11160#discussion_r383184923
 
 

 ##########
 File path: flink-core/src/main/java/org/apache/flink/core/memory/MemoryUtils.java
 ##########
 @@ -60,32 +63,31 @@
 		}
 	}
 
-	/** Should not be instantiated. */
-	private MemoryUtils() {}
-
-	private static Constructor<? extends ByteBuffer> getDirectBufferPrivateConstructor() {
+	private static long getClassFieldOffset(@SuppressWarnings("SameParameterValue") Class<?> cl, String fieldName) {
+		final String errorMessage = "Could not get field '" + fieldName + "' offset in class '" + cl + "' for unsafe operations";
 		try {
-			Constructor<? extends ByteBuffer> constructor =
-				ByteBuffer.allocateDirect(1).getClass().getDeclaredConstructor(long.class, int.class);
-			constructor.setAccessible(true);
-			return constructor;
-		} catch (NoSuchMethodException e) {
-			throw new Error(
-				"The private constructor java.nio.DirectByteBuffer.<init>(long, int) is not available.",
-				e);
+			return UNSAFE.objectFieldOffset(cl.getDeclaredField(fieldName));
 		} catch (SecurityException e) {
-			throw new Error(
-				"The private constructor java.nio.DirectByteBuffer.<init>(long, int) is not available, " +
-					"permission denied by security manager",
-				e);
+			throw new Error(errorMessage + ", permission denied by security manager.", e);
+		} catch (NoSuchFieldException e) {
+			throw new Error(errorMessage, e);
 		} catch (Throwable t) {
-			throw new Error(
-				"Unclassified error while trying to access private constructor " +
-					"java.nio.DirectByteBuffer.<init>(long, int).",
-				t);
+			throw new Error(errorMessage + ", unclassified error", t);
+		}
+	}
+
+	private static Class<?> getClassByName(@SuppressWarnings("SameParameterValue") String className) {
+		//noinspection OverlyBroadCatchBlock
+		try {
+			return Class.forName(className);
+		} catch (Throwable e) {
 
 Review comment:
   Why don't we only catch `ClassNotFoundException` here?

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