StephanEwen commented on a change in pull request #8290: [FLINK-12070] [network] Implement new bounded blocking subpartitions URL: https://github.com/apache/flink/pull/8290#discussion_r282877883
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/BoundedBlockingSubpartitionMemory.java ########## @@ -0,0 +1,130 @@ +/* + * 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.flink.runtime.io.network.partition; + +import org.apache.flink.core.memory.MemorySegment; +import org.apache.flink.core.memory.MemorySegmentFactory; +import org.apache.flink.runtime.io.network.buffer.Buffer; +import org.apache.flink.runtime.io.network.buffer.FreeingBufferRecycler; +import org.apache.flink.runtime.io.network.buffer.NetworkBuffer; + +import javax.annotation.Nullable; + +import java.nio.ByteBuffer; +import java.nio.ByteOrder; + +import static org.apache.flink.util.Preconditions.checkArgument; + +/** + * Putting and getting of buffers to/from a region of memory. + * This class handles the headers, length encoding, memory slicing. + */ +final class BoundedBlockingSubpartitionMemory { + + // all fields and methods below here have package-private access to avoid bridge + // methods when accessing them from the nested classes + + static final int HEADER_LENGTH = 8; + + static final int HEADER_VALUE_IS_BUFFER = 0; + + static final int HEADER_VALUE_IS_EVENT = 1; + + static ByteBuffer checkAndConfigureByteBuffer(ByteBuffer buffer) { + checkArgument(buffer.position() == 0); + checkArgument(buffer.capacity() > 8); + checkArgument(buffer.limit() == buffer.capacity()); + + return buffer.order(ByteOrder.nativeOrder()); + } + + // ------------------------------------------------------------------------ + + static final class Writer { + + private final ByteBuffer memory; + + Writer(ByteBuffer memory) { + this.memory = checkAndConfigureByteBuffer(memory); + } + + public boolean writeBuffer(Buffer buffer) { + final ByteBuffer memory = this.memory; + final int bufferSize = buffer.getSize(); + + if (memory.remaining() < bufferSize + HEADER_LENGTH) { + return false; + } + + memory.putInt(buffer.isBuffer() ? HEADER_VALUE_IS_BUFFER : HEADER_VALUE_IS_EVENT); + memory.putInt(bufferSize); + memory.put(buffer.getNioBufferReadable()); + return true; + } + + public ByteBuffer complete() { + memory.flip(); + return memory; + } + + public int getNumBytes() { + return memory.position(); + } + } + + static final class Reader { + + private final ByteBuffer memory; + + Reader(ByteBuffer memory) { + this.memory = checkAndConfigureByteBuffer(memory); + } + + @Nullable + public Buffer sliceNextBuffer() { + final ByteBuffer memory = this.memory; + final int remaining = memory.remaining(); + + // we only check the correct case where data is exhausted + // all other cases can only occur if our write logic is wrong and will already throw + // buffer underflow exceptions which will cause the read to fail. + if (remaining == 0) { + return null; + } + + final int header = memory.getInt(); + final int size = memory.getInt(); + + memory.limit(memory.position() + size); + ByteBuffer buf = memory.slice(); + memory.position(memory.limit()); + memory.limit(memory.capacity()); Review comment: If we don't set the limit forward, the successive `readInt()` calls for the header will fail. I played around with some alternatives, but could not find any where the code overall would become simpler. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
