/*
 * Consumer.java February 2007
 *
 * Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
 *
 * 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 org.simpleframework.http.message;

import java.io.IOException;

import org.simpleframework.transport.Cursor;

/**
 * The <code>Consumer</code> object is used to consume and process bytes from a
 * cursor. This is used to consume bytes from a pipeline and process the content
 * in order to produce a valid HTTP message. Using a consumer allows the server
 * to gather and process the data from the stream bit by bit without blocking.
 * <p>
 * A consumer has completed its task when it has either exhausted its stream, or
 * when it has consume a terminal token. For instance a consumer for a HTTP
 * header will have two <code>CRLF</code> bytes tokens to identify the end of
 * the header, once this has been read any excess bytes are reset on the cursor
 * and it has finished.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.transport.Cursor
 */
public interface Consumer {

    /**
     * This method is used to consume bytes from the provided cursor. Consuming
     * of bytes from the cursor should be done in such a way that it does not
     * block. So typically only the number of ready bytes in the
     * <code>Cursor</code> object should be read. If there are no ready bytes
     * then this method should return.
     * 
     * @param cursor
     *            used to consume the bytes from the HTTP pipeline
     */
    void consume(Cursor cursor) throws IOException;

    /**
     * This is used to determine whether the consumer has finished reading. The
     * consumer is considered finished if it has read a terminal token or if it
     * has exhausted the stream and can not read any more. Once finished the
     * consumed bytes can be parsed.
     * 
     * @return true if the consumer has finished reading its content
     */
    boolean isFinished();
}