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 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed 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.undertow.io;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import io.undertow.UndertowMessages;
import io.undertow.server.HttpServerExchange;
import io.undertow.util.Headers;
import org.xnio.Buffers;
import io.undertow.connector.ByteBufferPool;
import io.undertow.connector.PooledByteBuffer;
import org.xnio.channels.Channels;
import org.xnio.channels.StreamSinkChannel;

import static org.xnio.Bits.anyAreClear;
import static org.xnio.Bits.anyAreSet;

Buffering output stream that wraps a channel.

This stream delays channel creation, so if a response will fit in the buffer it is not necessary to
set the content length header.
Author:
Stuart Douglas/**
 * Buffering output stream that wraps a channel.
 * <p>
 * This stream delays channel creation, so if a response will fit in the buffer it is not necessary to
 * set the content length header.
 *
 * @author Stuart Douglas
 */
public class UndertowOutputStream extends OutputStream implements BufferWritableOutputStream {

    private final HttpServerExchange exchange;
    private ByteBuffer buffer;
    private PooledByteBuffer pooledBuffer;
    private StreamSinkChannel channel;
    private int state;
    private long written;
    private final long contentLength;

    private static final int FLAG_CLOSED = 1;
    private static final int FLAG_WRITE_STARTED = 1 << 1;

    private static final int MAX_BUFFERS_TO_ALLOCATE = 10;

    
Construct a new instance.  No write timeout is configured.
Params:
exchange – The exchange/**
     * Construct a new instance.  No write timeout is configured.
     *
     * @param exchange The exchange
     */
    public UndertowOutputStream(HttpServerExchange exchange) {
        this.exchange = exchange;
        this.contentLength = exchange.getResponseContentLength();
    }


    
If the response has not yet been written to the client this method will clear the streams buffer,
invalidating any content that has already been written. If any content has already been sent to the client then
this method will throw and IllegalStateException
Throws:
IllegalStateException – If the response has been commited/**
     * If the response has not yet been written to the client this method will clear the streams buffer,
     * invalidating any content that has already been written. If any content has already been sent to the client then
     * this method will throw and IllegalStateException
     *
     * @throws java.lang.IllegalStateException If the response has been commited
     */
    public void resetBuffer() {
        if(anyAreSet(state, FLAG_WRITE_STARTED)) {
            throw UndertowMessages.MESSAGES.cannotResetBuffer();
        }
        if(pooledBuffer != null) {
            pooledBuffer.close();
            pooledBuffer = null;
        }

    }

    public long getBytesWritten() {
        return written;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public void write(final int b) throws IOException {
        write(new byte[]{(byte) b}, 0, 1);
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public void write(final byte[] b) throws IOException {
        write(b, 0, b.length);
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public void write(final byte[] b, final int off, final int len) throws IOException {
        if (len < 1) {
            return;
        }
        if(Thread.currentThread() == exchange.getIoThread()) {
            throw UndertowMessages.MESSAGES.blockingIoFromIOThread();
        }
        if (anyAreSet(state, FLAG_CLOSED)) {
            throw UndertowMessages.MESSAGES.streamIsClosed();
        }
        //if this is the last of the content
        ByteBuffer buffer = buffer();
        if (len == contentLength - written || buffer.remaining() < len) {
            if (buffer.remaining() < len) {

                //so what we have will not fit.
                //We allocate multiple buffers up to MAX_BUFFERS_TO_ALLOCATE
                //and put it in them
                //if it still dopes not fit we loop, re-using these buffers

                StreamSinkChannel channel = this.channel;
                if (channel == null) {
                    this.channel = channel = exchange.getResponseChannel();
                }
                final ByteBufferPool bufferPool = exchange.getConnection().getByteBufferPool();
                ByteBuffer[] buffers = new ByteBuffer[MAX_BUFFERS_TO_ALLOCATE + 1];
                PooledByteBuffer[] pooledBuffers = new PooledByteBuffer[MAX_BUFFERS_TO_ALLOCATE];
                try {
                    buffers[0] = buffer;
                    int bytesWritten = 0;
                    int rem = buffer.remaining();
                    buffer.put(b, bytesWritten + off, rem);
                    buffer.flip();
                    bytesWritten += rem;
                    int bufferCount = 1;
                    for (int i = 0; i < MAX_BUFFERS_TO_ALLOCATE; ++i) {
                        PooledByteBuffer pooled = bufferPool.allocate();
                        pooledBuffers[bufferCount - 1] = pooled;
                        buffers[bufferCount++] = pooled.getBuffer();
                        ByteBuffer cb = pooled.getBuffer();
                        int toWrite = len - bytesWritten;
                        if (toWrite > cb.remaining()) {
                            rem = cb.remaining();
                            cb.put(b, bytesWritten + off, rem);
                            cb.flip();
                            bytesWritten += rem;
                        } else {
                            cb.put(b, bytesWritten + off, len - bytesWritten);
                            bytesWritten = len;
                            cb.flip();
                            break;
                        }
                    }
                    Channels.writeBlocking(channel, buffers, 0, bufferCount);
                    while (bytesWritten < len) {
                        //ok, it did not fit, loop and loop and loop until it is done
                        bufferCount = 0;
                        for (int i = 0; i < MAX_BUFFERS_TO_ALLOCATE + 1; ++i) {
                            ByteBuffer cb = buffers[i];
                            cb.clear();
                            bufferCount++;
                            int toWrite = len - bytesWritten;
                            if (toWrite > cb.remaining()) {
                                rem = cb.remaining();
                                cb.put(b, bytesWritten + off, rem);
                                cb.flip();
                                bytesWritten += rem;
                            } else {
                                cb.put(b, bytesWritten + off, len - bytesWritten);
                                bytesWritten = len;
                                cb.flip();
                                break;
                            }
                        }
                        Channels.writeBlocking(channel, buffers, 0, bufferCount);
                    }
                    buffer.clear();
                } finally {
                    for (int i = 0; i < pooledBuffers.length; ++i) {
                        PooledByteBuffer p = pooledBuffers[i];
                        if (p == null) {
                            break;
                        }
                        p.close();
                    }
                }
            } else {
                buffer.put(b, off, len);
                if (buffer.remaining() == 0) {
                    writeBufferBlocking(false);
                }
            }
        } else {
            buffer.put(b, off, len);
            if (buffer.remaining() == 0) {
                writeBufferBlocking(false);
            }
        }
        updateWritten(len);
    }

    @Override
    public void write(ByteBuffer[] buffers) throws IOException {
        if (anyAreSet(state, FLAG_CLOSED)) {
            throw UndertowMessages.MESSAGES.streamIsClosed();
        }
        int len = 0;
        for (ByteBuffer buf : buffers) {
            len += buf.remaining();
        }
        if (len < 1) {
            return;
        }

        //if we have received the exact amount of content write it out in one go
        //this is a common case when writing directly from a buffer cache.
        if (this.written == 0 && len == contentLength) {
            if (channel == null) {
                channel = exchange.getResponseChannel();
            }
            Channels.writeBlocking(channel, buffers, 0, buffers.length);
            state |= FLAG_WRITE_STARTED;
        } else {
            ByteBuffer buffer = buffer();
            if (len < buffer.remaining()) {
                Buffers.copy(buffer, buffers, 0, buffers.length);
            } else {
                if (channel == null) {
                    channel = exchange.getResponseChannel();
                }
                if (buffer.position() == 0) {
                    Channels.writeBlocking(channel, buffers, 0, buffers.length);
                } else {
                    final ByteBuffer[] newBuffers = new ByteBuffer[buffers.length + 1];
                    buffer.flip();
                    newBuffers[0] = buffer;
                    System.arraycopy(buffers, 0, newBuffers, 1, buffers.length);
                    Channels.writeBlocking(channel, newBuffers, 0, newBuffers.length);
                    buffer.clear();
                }
                state |= FLAG_WRITE_STARTED;
            }
        }
        updateWritten(len);
    }

    @Override
    public void write(ByteBuffer byteBuffer) throws IOException {
        write(new ByteBuffer[]{byteBuffer});
    }

    void updateWritten(final long len) throws IOException {
        this.written += len;
        if (contentLength != -1 && this.written >= contentLength) {
            flush();
            close();
        }
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public void flush() throws IOException {
        if (anyAreSet(state, FLAG_CLOSED)) {
            throw UndertowMessages.MESSAGES.streamIsClosed();
        }
        if (buffer != null && buffer.position() != 0) {
            writeBufferBlocking(false);
        }
        if (channel == null) {
            channel = exchange.getResponseChannel();
        }
        Channels.flushBlocking(channel);
    }

    private void writeBufferBlocking(final boolean writeFinal) throws IOException {
        if (channel == null) {
            channel = exchange.getResponseChannel();
        }
        buffer.flip();

        while (buffer.hasRemaining()) {
            if(writeFinal) {
                channel.writeFinal(buffer);
            } else {
                channel.write(buffer);
            }
            if(buffer.hasRemaining()) {
                channel.awaitWritable();
            }
        }
        buffer.clear();
        state |= FLAG_WRITE_STARTED;
    }
    @Override
    public void transferFrom(FileChannel source) throws IOException {
        if (anyAreSet(state, FLAG_CLOSED)) {
            throw UndertowMessages.MESSAGES.streamIsClosed();
        }
        if (buffer != null && buffer.position() != 0) {
            writeBufferBlocking(false);
        }
        if (channel == null) {
            channel = exchange.getResponseChannel();
        }
        long position = source.position();
        long size = source.size();
        Channels.transferBlocking(channel, source, position, size);
        updateWritten(size - position);
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public void close() throws IOException {
        if (anyAreSet(state, FLAG_CLOSED)) return;
        try {
            state |= FLAG_CLOSED;
            if (anyAreClear(state, FLAG_WRITE_STARTED) && channel == null) {
                if (buffer == null) {
                    exchange.getResponseHeaders().put(Headers.CONTENT_LENGTH, "0");
                } else {
                    exchange.getResponseHeaders().put(Headers.CONTENT_LENGTH, "" + buffer.position());
                }
            }
            if (buffer != null) {
                writeBufferBlocking(true);
            }
            if (channel == null) {
                channel = exchange.getResponseChannel();
            }
            if(channel == null) {
                return;
            }
            StreamSinkChannel channel = this.channel;
            channel.shutdownWrites();
            Channels.flushBlocking(channel);
        } finally {
            if (pooledBuffer != null) {
                pooledBuffer.close();
                buffer = null;
            } else {
                buffer = null;
            }
        }
    }

    private ByteBuffer buffer() {
        ByteBuffer buffer = this.buffer;
        if (buffer != null) {
            return buffer;
        }
        this.pooledBuffer = exchange.getConnection().getByteBufferPool().allocate();
        this.buffer = pooledBuffer.getBuffer();
        return this.buffer;
    }

}