IovArray.java — netty Source File

Source Code

/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project 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:
 *
 *   https://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 io.netty.channel.unix;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelOutboundBuffer.MessageProcessor;
import io.netty.util.internal.CleanableDirectBuffer;
import io.netty.util.internal.PlatformDependent;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

import static io.netty.channel.unix.Limits.IOV_MAX;
import static io.netty.channel.unix.Limits.SSIZE_MAX;
import static io.netty.util.internal.ObjectUtil.checkPositive;
import static java.lang.Math.min;

/**
 * Represent an array of struct array and so can be passed directly over via JNI without the need to do any more
 * array copies.
 *
 * The buffers are written out directly into direct memory to match the struct iov. See also {@code man writev}.
 *
 * <pre>
 * struct iovec {
 *   void  *iov_base;
 *   size_t iov_len;
 * };
 * </pre>
 *
 * See also
 * <a href="https://rkennke.wordpress.com/2007/07/30/efficient-jni-programming-iv-wrapping-native-data-objects/"
 * >Efficient JNI programming IV: Wrapping native data objects</a>.
 */
public final class IovArray implements MessageProcessor {

    /** The size of an address which should be 8 for 64 bits and 4 for 32 bits. */
    private static final int ADDRESS_SIZE = Buffer.addressSize();

    /**
     * The size of an {@code iovec} struct in bytes. This is calculated as we have 2 entries each of the size of the
     * address.
     */
    public static final int IOV_SIZE = 2 * ADDRESS_SIZE;

    /**
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