[GitHub] [arrow] rymurr commented on a change in pull request #7347: ARROW-8230: [Java] Remove netty dependency from arrow-memory

[GitBox <gi...@apache.org>]

rymurr commented on a change in pull request #7347:
URL: https://github.com/apache/arrow/pull/7347#discussion_r440896771



##########
File path: java/memory/src/main/java/org/apache/arrow/memory/util/MemoryUtil.java
##########
@@ -78,6 +77,55 @@ public Object run() {
       Field addressField = java.nio.Buffer.class.getDeclaredField("address");
       addressField.setAccessible(true);
       BYTE_BUFFER_ADDRESS_OFFSET = UNSAFE.objectFieldOffset(addressField);
+
+      Constructor<?> directBufferConstructor;
+      long address = -1;
+      final ByteBuffer direct = ByteBuffer.allocateDirect(1);
+      try {
+
+        final Object maybeDirectBufferConstructor =
+            AccessController.doPrivileged(new PrivilegedAction<Object>() {
+              @Override
+              public Object run() {
+                try {
+                  final Constructor<?> constructor =
+                      direct.getClass().getDeclaredConstructor(long.class, int.class);
+                  constructor.setAccessible(true);
+                  return constructor;
+                } catch (NoSuchMethodException e) {
+                  return e;
+                } catch (SecurityException e) {
+                  return e;
+                }
+              }
+            });
+
+        if (maybeDirectBufferConstructor instanceof Constructor<?>) {
+          address = UNSAFE.allocateMemory(1);
+          // try to use the constructor now
+          try {
+            ((Constructor<?>) maybeDirectBufferConstructor).newInstance(address, 1);
+            directBufferConstructor = (Constructor<?>) maybeDirectBufferConstructor;
+            logger.debug("direct buffer constructor: available");
+          } catch (InstantiationException e) {
+            directBufferConstructor = null;

Review comment:
       sure, any suggestions where? Note: This is taken from PlatformDependent0 in netty (logs and all).




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