/*
 * Copyright 2012 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.handler.codec.http;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelPipeline;
import io.netty.handler.codec.TooLongFrameException;


Decodes ByteBufs into HttpResponses and HttpContents. 
Parameters that prevents excessive memory consumption


Name
Meaning


maxInitialLineLength
The maximum length of the initial line (e.g. "HTTP/1.0 200 OK") If the length of the initial line exceeds this value, a TooLongFrameException will be raised.


maxHeaderSize
The maximum length of all headers. If the sum of the length of each header exceeds this value, a TooLongFrameException will be raised.


maxChunkSize
The maximum length of the content or each chunk. If the content length exceeds this value, the transfer encoding of the decoded response will be converted to 'chunked' and the content will be split into multiple HttpContents. If the transfer encoding of the HTTP response is 'chunked' already, each chunk will be split into smaller chunks if the length of the chunk exceeds this value. If you prefer not to handle HttpContents in your handler, insert HttpObjectAggregator after this decoder in the ChannelPipeline.


Decoding a response for a HEAD request

Unlike other HTTP requests, the successful response of a HEAD
request does not have any content even if there is Content-Length header. Because HttpResponseDecoder is not able to determine if the response currently being decoded is associated with a HEAD request, you must override HttpObjectDecoder.isContentAlwaysEmpty(HttpMessage) to return true for the response of the HEAD request.

If you are writing an HTTP client that issues a HEAD request, please use HttpClientCodec instead of this decoder. It will perform additional state management to handle the responses for HEAD
requests correctly.

Decoding a response for a CONNECT request

You also need to do additional state management to handle the response of a
CONNECT request properly, like you did for HEAD.  One
difference is that the decoder should stop decoding completely after decoding
the successful 200 response since the connection is not an HTTP connection
anymore.
 HttpClientCodec also handles this edge case correctly, so you have to use HttpClientCodec if you are writing an HTTP client that issues a CONNECT request.

/**
 * Decodes {@link ByteBuf}s into {@link HttpResponse}s and
 * {@link HttpContent}s.
 *
 * <h3>Parameters that prevents excessive memory consumption</h3>
 * <table border="1">
 * <tr>
 * <th>Name</th><th>Meaning</th>
 * </tr>
 * <tr>
 * <td>{@code maxInitialLineLength}</td>
 * <td>The maximum length of the initial line (e.g. {@code "HTTP/1.0 200 OK"})
 *     If the length of the initial line exceeds this value, a
 *     {@link TooLongFrameException} will be raised.</td>
 * </tr>
 * <tr>
 * <td>{@code maxHeaderSize}</td>
 * <td>The maximum length of all headers.  If the sum of the length of each
 *     header exceeds this value, a {@link TooLongFrameException} will be raised.</td>
 * </tr>
 * <tr>
 * <td>{@code maxChunkSize}</td>
 * <td>The maximum length of the content or each chunk.  If the content length
 *     exceeds this value, the transfer encoding of the decoded response will be
 *     converted to 'chunked' and the content will be split into multiple
 *     {@link HttpContent}s.  If the transfer encoding of the HTTP response is
 *     'chunked' already, each chunk will be split into smaller chunks if the
 *     length of the chunk exceeds this value.  If you prefer not to handle
 *     {@link HttpContent}s in your handler, insert {@link HttpObjectAggregator}
 *     after this decoder in the {@link ChannelPipeline}.</td>
 * </tr>
 * </table>
 *
 * <h3>Decoding a response for a <tt>HEAD</tt> request</h3>
 * <p>
 * Unlike other HTTP requests, the successful response of a <tt>HEAD</tt>
 * request does not have any content even if there is <tt>Content-Length</tt>
 * header.  Because {@link HttpResponseDecoder} is not able to determine if the
 * response currently being decoded is associated with a <tt>HEAD</tt> request,
 * you must override {@link #isContentAlwaysEmpty(HttpMessage)} to return
 * <tt>true</tt> for the response of the <tt>HEAD</tt> request.
 * </p><p>
 * If you are writing an HTTP client that issues a <tt>HEAD</tt> request,
 * please use {@link HttpClientCodec} instead of this decoder.  It will perform
 * additional state management to handle the responses for <tt>HEAD</tt>
 * requests correctly.
 * </p>
 *
 * <h3>Decoding a response for a <tt>CONNECT</tt> request</h3>
 * <p>
 * You also need to do additional state management to handle the response of a
 * <tt>CONNECT</tt> request properly, like you did for <tt>HEAD</tt>.  One
 * difference is that the decoder should stop decoding completely after decoding
 * the successful 200 response since the connection is not an HTTP connection
 * anymore.
 * </p><p>
 * {@link HttpClientCodec} also handles this edge case correctly, so you have to
 * use {@link HttpClientCodec} if you are writing an HTTP client that issues a
 * <tt>CONNECT</tt> request.
 * </p>
 */
public class HttpResponseDecoder extends HttpObjectDecoder {

    private static final HttpResponseStatus UNKNOWN_STATUS = new HttpResponseStatus(999, "Unknown");

    
Creates a new instance with the default maxInitialLineLength (4096), maxHeaderSize (8192), and maxChunkSize (8192). /**
     * Creates a new instance with the default
     * {@code maxInitialLineLength (4096)}, {@code maxHeaderSize (8192)}, and
     * {@code maxChunkSize (8192)}.
     */
    public HttpResponseDecoder() {
    }

    
Creates a new instance with the specified parameters.
/**
     * Creates a new instance with the specified parameters.
     */
    public HttpResponseDecoder(
            int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
        super(maxInitialLineLength, maxHeaderSize, maxChunkSize, true);
    }

    public HttpResponseDecoder(
            int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean validateHeaders) {
        super(maxInitialLineLength, maxHeaderSize, maxChunkSize, true, validateHeaders);
    }

    public HttpResponseDecoder(
            int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean validateHeaders,
            int initialBufferSize) {
        super(maxInitialLineLength, maxHeaderSize, maxChunkSize, true, validateHeaders, initialBufferSize);
    }

    @Override
    protected HttpMessage createMessage(String[] initialLine) {
        return new DefaultHttpResponse(
                HttpVersion.valueOf(initialLine[0]),
                HttpResponseStatus.valueOf(Integer.parseInt(initialLine[1]), initialLine[2]), validateHeaders);
    }

    @Override
    protected HttpMessage createInvalidMessage() {
        return new DefaultFullHttpResponse(HttpVersion.HTTP_1_0, UNKNOWN_STATUS, validateHeaders);
    }

    @Override
    protected boolean isDecodingRequest() {
        return false;
    }
}