/*
 * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/ChunkedOutputStream.java,v 1.16 2004/05/13 04:03:25 mbecke Exp $
 * $Revision: 1.16 $
 * $Date: 2004/05/13 04:03:25 $
 *
 * ====================================================================
 *
 *  Copyright 2002-2004 The Apache Software Foundation
 *
 *  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.
 * ====================================================================
 *
 * 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.commons.httpclient;

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

import org.apache.commons.httpclient.util.EncodingUtil;

/**
 * Implements HTTP chunking support. Writes are buffered to an internal buffer (2048 default size).
 * Chunks are guaranteed to be at least as large as the buffer size (except for the last chunk).
 *
 * @author Mohammad Rezaei, Goldman, Sachs & Co.
 */
public class ChunkedOutputStream extends OutputStream {

    // ------------------------------------------------------- Static Variables
    private static final byte CRLF[] = new byte[] {(byte) 13, (byte) 10};

    /** End chunk */
    private static final byte ENDCHUNK[] = CRLF;

    /** 0 */
    private static final byte ZERO[] = new byte[] {(byte) '0'};

    // ----------------------------------------------------- Instance Variables
    private OutputStream stream = null;

    private byte[] cache;

    private int cachePosition = 0;

    private boolean wroteLastChunk = false;

    // ----------------------------------------------------------- Constructors
    /**
     * Wraps a stream and chunks the output.
     * @param stream to wrap
     * @param bufferSize minimum chunk size (excluding last chunk)
     * @throws IOException
     * 
     * @since 3.0
     */
    public ChunkedOutputStream(OutputStream stream, int bufferSize) throws IOException {
        this.cache = new byte[bufferSize];
        this.stream = stream;
    }

    /**
     * Wraps a stream and chunks the output. The default buffer size of 2048 was chosen because
     * the chunk overhead is less than 0.5%
     * @param stream
     * @throws IOException
     */
    public ChunkedOutputStream(OutputStream stream) throws IOException {
        this(stream, 2048);
    }

    // ----------------------------------------------------------- Internal methods
    /**
     * Writes the cache out onto the underlying stream
     * @throws IOException
     * 
     * @since 3.0
     */
    protected void flushCache() throws IOException {
        if (cachePosition > 0) {
            byte chunkHeader[] = EncodingUtil.getAsciiBytes(
                    Integer.toHexString(cachePosition) + "\r\n");
            stream.write(chunkHeader, 0, chunkHeader.length);
            stream.write(cache, 0, cachePosition);
            stream.write(ENDCHUNK, 0, ENDCHUNK.length);
            cachePosition = 0;
        }
    }

    /**
     * Writes the cache and bufferToAppend to the underlying stream
     * as one large chunk
     * @param bufferToAppend
     * @param off
     * @param len
     * @throws IOException
     * 
     * @since 3.0
     */
    protected void flushCacheWithAppend(byte bufferToAppend[], int off, int len) throws IOException {
        byte chunkHeader[] = EncodingUtil.getAsciiBytes(
                Integer.toHexString(cachePosition + len) + "\r\n");
        stream.write(chunkHeader, 0, chunkHeader.length);
        stream.write(cache, 0, cachePosition);
        stream.write(bufferToAppend, off, len);
        stream.write(ENDCHUNK, 0, ENDCHUNK.length);
        cachePosition = 0;
    }

    protected void writeClosingChunk() throws IOException {
        // Write the final chunk.

        stream.write(ZERO, 0, ZERO.length);
        stream.write(CRLF, 0, CRLF.length);
        stream.write(ENDCHUNK, 0, ENDCHUNK.length);
    }

    // ----------------------------------------------------------- Public Methods
    /**
     * Must be called to ensure the internal cache is flushed and the closing chunk is written.
     * @throws IOException
     * 
     * @since 3.0
     */
    public void finish() throws IOException {
        if (!wroteLastChunk) {
            flushCache();
            writeClosingChunk();
            wroteLastChunk = true;
        }
    }

    // -------------------------------------------- OutputStream Methods
    public void write(int b) throws IOException {
        cache[cachePosition] = (byte) b;
        cachePosition++;
        if (cachePosition == 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.
     * @param b
     * @throws IOException
     * 
     * @since 3.0
     */
    public void write(byte b[]) throws IOException {
        this.write(b, 0, b.length);
    }

    public void write(byte src[], int off, int len) throws IOException {
        if (len >= cache.length - cachePosition) {
            flushCacheWithAppend(src, off, len);
        } else {
            System.arraycopy(src, off, cache, cachePosition, len);
            cachePosition += len;
        }
    }

    /**
     * Flushes the underlying stream, but leaves the internal buffer alone.
     * @throws IOException
     */
    public void flush() throws IOException {
        stream.flush();
    }

    /**
     * Finishes writing to the underlying stream, but does NOT close the underlying stream.
     * @throws IOException
     */
    public void close() throws IOException {
        finish();
        super.close();
    }
}