/*
* 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.epoll;
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;
/**
* 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="http://rkennke.wordpress.com/2007/07/30/efficient-jni-programming-iv-wrapping-native-data-objects/"
* >Efficient JNI programming IV: Wrapping native data objects</a>.
*/
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 {@link Native#IOV_MAX} iov entries, where {@link Native#IOV_MAX} signified
* the maximum number of {@code iovec} structs that can be passed to {@code writev(...)}.
*/
private static final int CAPACITY = Native.IOV_MAX * IOV_SIZE;
private final long memoryAddress;
private int count;
private long size;
IovArray() {
memoryAddress = PlatformDependent.allocateMemory(CAPACITY);
}
void clear() {
count = 0;
size = 0;
}
/**
* Try to add the given {@link ByteBuf}. Returns {@code true} on success,
* {@code false} otherwise.
*/
boolean add(ByteBuf buf) {
if (count == Native.IOV_MAX) {
// No more room!
return false;
}
final int len = buf.readableBytes();
if (len == 0) {
// No need to add an empty buffer.
// We return true here because we want ChannelOutboundBuffer.forEachFlushedMessage() to continue
// fetching the next buffers.
return true;
}
final long addr = buf.memoryAddress();
final int offset = buf.readerIndex();
add(addr, offset, len);
return true;
}
private void add(long addr, int offset, int len) {
if (len == 0) {
// No need to add an empty buffer.
return;
}
final long baseOffset = memoryAddress(count++);
final long lengthOffset = baseOffset + ADDRESS_SIZE;
if (ADDRESS_SIZE == 8) {
// 64bit
PlatformDependent.putLong(baseOffset, addr + offset);
PlatformDependent.putLong(lengthOffset, len);
} else {
assert ADDRESS_SIZE == 4;
PlatformDependent.putInt(baseOffset, (int) addr + offset);
PlatformDependent.putInt(lengthOffset, len);
}
size += len;
}
/**
* Try to add the given {@link CompositeByteBuf}. Returns {@code true} on success,
* {@code false} otherwise.
*/
boolean add(CompositeByteBuf buf) {
ByteBuffer[] buffers = buf.nioBuffers();
if (count + buffers.length >= Native.IOV_MAX) {
// No more room!
return false;
}
for (int i = 0; i < buffers.length; i++) {
ByteBuffer nioBuffer = buffers[i];
int offset = nioBuffer.position();
int len = nioBuffer.limit() - nioBuffer.position();
if (len == 0) {
// No need to add an empty buffer so just continue
continue;
}
long addr = PlatformDependent.directBufferAddress(nioBuffer);
add(addr, offset, len);
}
return true;
}
/**
* Process the written iov entries. This will return the length of the iov entry on the given index if it is
* smaller then the given {@code written} value. Otherwise it returns {@code -1}.
*/
long processWritten(int index, long written) {
long baseOffset = memoryAddress(index);
long lengthOffset = baseOffset + ADDRESS_SIZE;
if (ADDRESS_SIZE == 8) {
// 64bit
long len = PlatformDependent.getLong(lengthOffset);
if (len > written) {
long offset = PlatformDependent.getLong(baseOffset);
PlatformDependent.putLong(baseOffset, offset + written);
PlatformDependent.putLong(lengthOffset, len - written);
return -1;
}
return len;
} else {
assert ADDRESS_SIZE == 4;
long len = PlatformDependent.getInt(lengthOffset);
if (len > written) {
int offset = PlatformDependent.getInt(baseOffset);
PlatformDependent.putInt(baseOffset, (int) (offset + written));
PlatformDependent.putInt(lengthOffset, (int) (len - written));
return -1;
}
return len;
}
}
/**
* Returns the number if iov entries.
*/
int count() {
return count;
}
/**
* Returns the size in bytes
*/
long size() {
return size;
}
/**
* Returns the {@code memoryAddress} for the given {@code offset}.
*/
long memoryAddress(int offset) {
return memoryAddress + IOV_SIZE * offset;
}
/**
* Release the {@link IovArray}. Once release further using of it may crash the JVM!
*/
void release() {
PlatformDependent.freeMemory(memoryAddress);
}
@Override
public boolean processMessage(Object msg) throws Exception {
if (msg instanceof ByteBuf) {
if (msg instanceof CompositeByteBuf) {
return add((CompositeByteBuf) msg);
} else {
return add((ByteBuf) msg);
}
}
return false;
}
}