/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.impl.io;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.http.io.SessionOutputBuffer;

Implements chunked transfer coding. The content is sent in small chunks.
Entities transferred using this output stream can be of unlimited length.
Writes are buffered to an internal buffer (2048 default size).

Note that this class NEVER closes the underlying stream, even when close
gets called.  Instead, the stream will be marked as closed and no further
output will be permitted.
Since:
4.0/**
 * Implements chunked transfer coding. The content is sent in small chunks.
 * Entities transferred using this output stream can be of unlimited length.
 * Writes are buffered to an internal buffer (2048 default size).
 * <p>
 * Note that this class NEVER closes the underlying stream, even when close
 * gets called.  Instead, the stream will be marked as closed and no further
 * output will be permitted.
 *
 *
 * @since 4.0
 */
public class ChunkedOutputStream extends OutputStream {

    // ----------------------------------------------------- Instance Variables
    private final SessionOutputBuffer out;

    private final byte[] cache;

    private int cachePosition = 0;

    private boolean wroteLastChunk = false;

    
True if the stream is closed. /** True if the stream is closed. */
    private boolean closed = false;

    
Wraps a session output buffer and chunk-encodes the output.
Params:
out – The session output buffer
bufferSize – The minimum chunk size (excluding last chunk)
Throws:
IOException – not thrown
Deprecated:
(4.3) use ChunkedOutputStream(int, SessionOutputBuffer)/**
     * Wraps a session output buffer and chunk-encodes the output.
     *
     * @param out The session output buffer
     * @param bufferSize The minimum chunk size (excluding last chunk)
     * @throws IOException not thrown
     *
     * @deprecated (4.3) use {@link ChunkedOutputStream#ChunkedOutputStream(int, SessionOutputBuffer)}
     */
    @Deprecated
    public ChunkedOutputStream(final SessionOutputBuffer out, final int bufferSize)
            throws IOException {
        this(bufferSize, out);
    }

    
Wraps a session output buffer and chunks the output. The default buffer
size of 2048 was chosen because the chunk overhead is less than 0.5%
Params:
out –       the output buffer to wrap
Throws:
IOException – not thrown
Deprecated:
(4.3) use ChunkedOutputStream(int, SessionOutputBuffer)/**
     * Wraps a session output buffer and chunks the output. The default buffer
     * size of 2048 was chosen because the chunk overhead is less than 0.5%
     *
     * @param out       the output buffer to wrap
     * @throws IOException not thrown
     *
     * @deprecated (4.3) use {@link ChunkedOutputStream#ChunkedOutputStream(int, SessionOutputBuffer)}
     */
    @Deprecated
    public ChunkedOutputStream(final SessionOutputBuffer out)
            throws IOException {
        this(2048, out);
    }

    
Wraps a session output buffer and chunk-encodes the output.
Params:
bufferSize – The minimum chunk size (excluding last chunk)
out – The session output buffer/**
     * Wraps a session output buffer and chunk-encodes the output.
     *
     * @param bufferSize The minimum chunk size (excluding last chunk)
     * @param out The session output buffer
     */
    public ChunkedOutputStream(final int bufferSize, final SessionOutputBuffer out) {
        super();
        this.cache = new byte[bufferSize];
        this.out = out;
    }

    
Writes the cache out onto the underlying stream
/**
     * Writes the cache out onto the underlying stream
     */
    protected void flushCache() throws IOException {
        if (this.cachePosition > 0) {
            this.out.writeLine(Integer.toHexString(this.cachePosition));
            this.out.write(this.cache, 0, this.cachePosition);
            this.out.writeLine("");
            this.cachePosition = 0;
        }
    }

    
Writes the cache and bufferToAppend to the underlying stream
as one large chunk
/**
     * Writes the cache and bufferToAppend to the underlying stream
     * as one large chunk
     */
    protected void flushCacheWithAppend(final byte bufferToAppend[], final int off, final int len) throws IOException {
        this.out.writeLine(Integer.toHexString(this.cachePosition + len));
        this.out.write(this.cache, 0, this.cachePosition);
        this.out.write(bufferToAppend, off, len);
        this.out.writeLine("");
        this.cachePosition = 0;
    }

    protected void writeClosingChunk() throws IOException {
        // Write the final chunk.
        this.out.writeLine("0");
        this.out.writeLine("");
    }

    // ----------------------------------------------------------- Public Methods
    
Must be called to ensure the internal cache is flushed and the closing
chunk is written.
Throws:
IOException – in case of an I/O error/**
     * Must be called to ensure the internal cache is flushed and the closing
     * chunk is written.
     * @throws IOException in case of an I/O error
     */
    public void finish() throws IOException {
        if (!this.wroteLastChunk) {
            flushCache();
            writeClosingChunk();
            this.wroteLastChunk = true;
        }
    }

    // -------------------------------------------- OutputStream Methods
    @Override
    public void write(final int b) throws IOException {
        if (this.closed) {
            throw new IOException("Attempted write to closed stream.");
        }
        this.cache[this.cachePosition] = (byte) b;
        this.cachePosition++;
        if (this.cachePosition == this.cache.length) {
            flushCache();
        }
    }

    
Writes the array. If the array does not fit within the buffer, it is
not split, but rather written out as one large chunk.
/**
     * Writes the array. If the array does not fit within the buffer, it is
     * not split, but rather written out as one large chunk.
     */
    @Override
    public void write(final byte b[]) throws IOException {
        write(b, 0, b.length);
    }

    
Writes the array. If the array does not fit within the buffer, it is
not split, but rather written out as one large chunk.
/**
     * Writes the array. If the array does not fit within the buffer, it is
     * not split, but rather written out as one large chunk.
     */
    @Override
    public void write(final byte src[], final int off, final int len) throws IOException {
        if (this.closed) {
            throw new IOException("Attempted write to closed stream.");
        }
        if (len >= this.cache.length - this.cachePosition) {
            flushCacheWithAppend(src, off, len);
        } else {
            System.arraycopy(src, off, cache, this.cachePosition, len);
            this.cachePosition += len;
        }
    }

    
Flushes the content buffer and the underlying stream.
/**
     * Flushes the content buffer and the underlying stream.
     */
    @Override
    public void flush() throws IOException {
        flushCache();
        this.out.flush();
    }

    
Finishes writing to the underlying stream, but does NOT close the underlying stream.
/**
     * Finishes writing to the underlying stream, but does NOT close the underlying stream.
     */
    @Override
    public void close() throws IOException {
        if (!this.closed) {
            this.closed = true;
            finish();
            this.out.flush();
        }
    }
}