Compression.java

/*
 * 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.
 */
package org.apache.sshd.common;

import java.io.IOException;

import org.apache.sshd.common.util.Buffer;

/**
 * Interface used to compress the stream of data between the
 * SSH server and clients.
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public interface Compression {

    /**
     * Enum identifying if this object will be used to compress
     * or uncompress data.
     */
    enum Type {
        Inflater,
        Deflater
    }

    /**
     * Delayed compression is an Open-SSH specific feature which
     * informs both the client and server to not compress data before
     * the session has been authenticated.
     *
     * @return if the compression is delayed after authentication or not
     */
    boolean isDelayed();

    /**
     * Initialize this object to either compress or uncompress data.
     * This method must be called prior to any calls to either
     * <code>compress</code> or <code>uncompress</code>.
     * Once the object has been initialized, only one of
     * <code>compress</code> or <code>uncompress</code> methods can be
     * called.
     *
     * @param type
     * @param level
     */
    void init(Type type, int level);

    /**
     * Compress the given buffer in place.
     *
     * @param buffer the buffer containing the data to compress
     * @throws IOException if an error occurs
     */
    void compress(Buffer buffer) throws IOException;

    /**
     * Uncompress the data in a buffer into another buffer.
     *
     * @param from the buffer containing the data to uncompress
     * @param to the buffer receiving the uncompressed data
     * @throws IOException if an error occurs
     */
    void uncompress(Buffer from, Buffer to) throws IOException;

}