software.amazon.awssdk.thirdparty.io.netty.channel.unix.IovArray Maven / Gradle / Ivy
/*
* 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:
*
* 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 io.netty.channel.unix;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.CompositeByteBuf;
import io.netty.channel.ChannelOutboundBuffer.MessageProcessor;
import io.netty.util.internal.PlatformDependent;
import java.nio.ByteBuffer;
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 io.netty.util.internal.PlatformDependent.allocateMemory;
import static io.netty.util.internal.PlatformDependent.directBufferAddress;
import static io.netty.util.internal.PlatformDependent.freeMemory;
import static io.netty.util.internal.PlatformDependent.putInt;
import static io.netty.util.internal.PlatformDependent.putLong;
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}.
*
*
* struct iovec {
* void *iov_base;
* size_t iov_len;
* };
*
*
* See also
* Efficient JNI programming IV: Wrapping native data objects.
*/
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 = PlatformDependent.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.
*/
private static final int IOV_SIZE = 2 * ADDRESS_SIZE;
/**
* The needed memory to hold up to {@code IOV_MAX} iov entries, where {@code IOV_MAX} signified
* the maximum number of {@code iovec} structs that can be passed to {@code writev(...)}.
*/
private static final int CAPACITY = IOV_MAX * IOV_SIZE;
private final long memoryAddress;
private int count;
private long size;
private long maxBytes = SSIZE_MAX;
public IovArray() {
memoryAddress = allocateMemory(CAPACITY);
}
public void clear() {
count = 0;
size = 0;
}
/**
* Add a {@link ByteBuf} to this {@link IovArray}.
* @param buf The {@link ByteBuf} to add.
* @return {@code true} if the entire {@link ByteBuf} has been added to this {@link IovArray}. Note in the event
* that {@link ByteBuf} is a {@link CompositeByteBuf} {@code false} may be returned even if some of the components
* have been added.
*/
public boolean add(ByteBuf buf) {
if (count == IOV_MAX) {
// No more room!
return false;
} else if (buf.hasMemoryAddress() && buf.nioBufferCount() == 1) {
final int len = buf.readableBytes();
return len == 0 || add(buf.memoryAddress(), buf.readerIndex(), len);
} else {
ByteBuffer[] buffers = buf.nioBuffers();
for (ByteBuffer nioBuffer : buffers) {
final int len = nioBuffer.remaining();
if (len != 0 && (!add(directBufferAddress(nioBuffer), nioBuffer.position(), len) || count == IOV_MAX)) {
return false;
}
}
return true;
}
}
private boolean add(long addr, int offset, int len) {
final long baseOffset = memoryAddress(count);
final long lengthOffset = baseOffset + ADDRESS_SIZE;
// If there is at least 1 entry then we enforce the maximum bytes. We want to accept at least one entry so we
// will attempt to write some data and make progress.
if (maxBytes - len < size && count > 0) {
// If the size + len will overflow SSIZE_MAX we stop populate the IovArray. This is done as linux
// not allow to write more bytes then SSIZE_MAX with one writev(...) call and so will
// return 'EINVAL', which will raise an IOException.
//
// See also:
// - http://linux.die.net/man/2/writev
return false;
}
size += len;
++count;
if (ADDRESS_SIZE == 8) {
// 64bit
putLong(baseOffset, addr + offset);
putLong(lengthOffset, len);
} else {
assert ADDRESS_SIZE == 4;
putInt(baseOffset, (int) addr + offset);
putInt(lengthOffset, len);
}
return true;
}
/**
* Returns the number if iov entries.
*/
public int count() {
return count;
}
/**
* Returns the size in bytes
*/
public long size() {
return size;
}
/**
* Set the maximum amount of bytes that can be added to this {@link IovArray} via {@link #add(ByteBuf)}.
*
* This will not impact the existing state of the {@link IovArray}, and only applies to subsequent calls to
* {@link #add(ByteBuf)}.
*
* In order to ensure some progress is made at least one {@link ByteBuf} will be accepted even if it's size exceeds
* this value.
* @param maxBytes the maximum amount of bytes that can be added to this {@link IovArray} via {@link #add(ByteBuf)}.
*/
public void maxBytes(long maxBytes) {
this.maxBytes = min(SSIZE_MAX, checkPositive(maxBytes, "maxBytes"));
}
/**
* Get the maximum amount of bytes that can be added to this {@link IovArray} via {@link #add(ByteBuf)}.
* @return the maximum amount of bytes that can be added to this {@link IovArray} via {@link #add(ByteBuf)}.
*/
public long maxBytes() {
return maxBytes;
}
/**
* Returns the {@code memoryAddress} for the given {@code offset}.
*/
public long memoryAddress(int offset) {
return memoryAddress + IOV_SIZE * offset;
}
/**
* Release the {@link IovArray}. Once release further using of it may crash the JVM!
*/
public void release() {
freeMemory(memoryAddress);
}
@Override
public boolean processMessage(Object msg) throws Exception {
return (msg instanceof ByteBuf) && add((ByteBuf) msg);
}
}