platform/core.output2/src/org/netbeans/core/output2/Storage.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.
 */
/*
 * Storage.java
 *
 * Created on May 14, 2004, 1:40 PM
 */

package org.netbeans.core.output2;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * Storage abstraction for output writer - plan is to eventually do both
 * heap-based and mapped file based storages.
 *
 * @author  Tim Boudreau, Jesse Glick
 */
interface Storage {
    /**
     * Get a BufferResource for reading over the storage,
     * starting at the specified byte position and containing the
     * specified number of bytes.
     *
     * @param start The start byte
     * @param length How many bytes
     * @return A byte buffer
     * @throws IOException if there is a problem reading or allocating the buffer
     */
    public BufferResource<ByteBuffer> getReadBuffer (int start, int length) throws IOException;
    /**
     * Get a buffer for <strong>appending</strong> <code>length</code> bytes to the stored data.  Note that
     * writing into the returned buffer does not automatically write to the file - the returned buffer should
     * be passed to <code>write(ByteBuffer b)</code> to be saved once it has been filled.
     *
     * @param length The number of bytes to write
     * @return
     * @throws IOException
     */
    public ByteBuffer getWriteBuffer (int length) throws IOException;
    /**
     * Write a ByteBuffer (presumably obtained from getWriteBuffer()) to persistent storage.  The buffer
     * may be underfilled; data will be written to the <code>limit</code> of the ByteBuffer, disregarding any
     * additional capacity.
     *
     * @param buf A ByteBuffer with data to write
     * @return The byte position of the <strong>start</strong> of data written
     * @throws IOException if there is a problem writing the data
     */
    public int write (ByteBuffer buf) throws IOException;

    /**
     * Remove bytes from the end of the file. Only removing characters from the
     * last unfinished line is supported.
     *
     * @param length Number of bytes to remove.
     * @throws IOException if there is a problem writing the data.
     */
    public void removeBytesFromEnd(int length) throws IOException;

    /**
     * Dispose of this storage, deleting all associated resources, files, data storage, etc.  This should only
     * be called after it is absolutely certain that nothing will try to write further data to the storage.
     *
     */
    public void dispose ();

    /**
     * The number of bytes currently occupied by written data
     *
     * @return A byte count
     */
    public int size();

    /**
     * For storages that implement a lazy writing scheme, force any pending data to be written to the storage.
     *
     * @throws IOException If there is a problem writing the data
     */
    public void flush() throws IOException;

    /**
     * Close the storage for <strong>writing</strong> disposing of any resources used for writing to the storage,
     * but leaving it in a state where it may be read, calling <code>flush()</code> if necessary.  Subsequent calls
     * to write methods may reopen the storage for writing as needed.
     *
     * @throws IOException If there is a problem writing to the persistent storage
     */
    public void close() throws IOException;

    /**
     * Determine if close() has been called on this storage.  Primarily used for cases where the gui should
     * display some status information if a process is still writing to the storage.
     *
     * @return true if the storage has been closed
     */
    public boolean isClosed();

    /**
     * Shift start of the first character by specified offset. This method is
     * called when a limit is reached and some part of the output should be
     * forgotten.
     *
     * @param byteOffset How many bytes should be forgotten.
     */
    public void shiftStart(int byteOffset);
}