roee88 commented on a change in pull request #11067: URL: https://github.com/apache/arrow/pull/11067#discussion_r705882401
########## File path: java/ffi/src/main/java/org/apache/arrow/ffi/FFIReferenceManager.java ########## @@ -0,0 +1,117 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.arrow.ffi; + +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.arrow.memory.ArrowBuf; +import org.apache.arrow.memory.BufferAllocator; +import org.apache.arrow.memory.OwnershipTransferResult; +import org.apache.arrow.memory.ReferenceManager; +import org.apache.arrow.util.Preconditions; + +/** + * A ReferenceManager implementation that holds a {@link org.apache.arrow.ffi.BaseStruct}. + * <p> + * A reference count is maintained and once it reaches zero the struct + * is released (as per the C data interface specification) and closed. + */ +final class FFIReferenceManager implements ReferenceManager { + private final AtomicInteger bufRefCnt = new AtomicInteger(0); + + private final BaseStruct struct; + + FFIReferenceManager(BaseStruct struct) { + this.struct = struct; + } + + @Override + public int getRefCount() { + return bufRefCnt.get(); + } + + @Override + public boolean release() { + return release(1); + } + + @Override + public boolean release(int decrement) { + Preconditions.checkState(decrement >= 1, "ref count decrement should be greater than or equal to 1"); + // decrement the ref count + final int refCnt = bufRefCnt.addAndGet(-decrement); + // the new ref count should be >= 0 + Preconditions.checkState(refCnt >= 0, "RefCnt has gone negative"); + if (refCnt == 0) { + // refcount of this reference manager has dropped to 0 + // release the underlying memory + synchronized (this) { Review comment: Given that the counter is atomic, in what scenario is it needed? I believe that if the counter is decremented to zero then it must be released. Incrementing the counter after (or during) shouldn't change the decision to release. I saw no special code for handling the increment-after-release case in other reference managers so I assume it's not possible by design. However, if desired I can add it just in case. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
