java/engine/org/apache/derby/impl/jdbc/LOBFile.java

/*

   Derby - Class org.apache.derby.impl.jdbc.LOBFile

   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.derby.impl.jdbc;

import java.io.FileNotFoundException;
import java.io.IOException;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.io.StorageFile;
import org.apache.derby.io.StorageRandomAccessFile;

/**
 * LOBFile is a wrapper over StorageRandomAccessFile. The purpose of this class
 * is to let the user of this class access StorageRandomAccessFile in plain and
 * in encrypted for without having to change code.
 */
class LOBFile {
    /** The temporary file where the contents of the LOB should be stored. */
    private final StorageFile storageFile;

    /** An object giving random access to {@link #storageFile}. */
    private final StorageRandomAccessFile randomAccessFile;

    /**
     * Constructs LOBFile.
     *
     * @param lobFile StorageFile object for which the file will be created
     * @throws FileNotFoundException if the file exists but is a directory or
     * cannot be opened
     */
    LOBFile(StorageFile lobFile) throws FileNotFoundException {
        storageFile = lobFile;
        randomAccessFile = lobFile.getRandomAccessFile("rw");
    }

    /**
     * Get the {@code StorageFile} which represents the file where the
     * contents of the LOB are stored.
     * @return a {@code StorageFile} instance
     */
    StorageFile getStorageFile() {
        return storageFile;
    }

    /**
     * Returns length of the file.
     * @return length of the file
     * @throws IOException if an I/O error occurs
     */
    long length() throws IOException {
        return randomAccessFile.length();
    }

    /**
     * Sets the file pointer to a given position.
     * @param pos new position
     * @throws IOException if an I/O error occurs
     */
    void seek(long pos) throws IOException {
        randomAccessFile.seek (pos);
    }

    /**
     * Writes one bytes into the file.
     * @param b int value of the byte
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    void write(int b) throws IOException, StandardException {
        randomAccessFile.write (b);
    }

    /**
     * Returns the current position of the file pointer.
     * @return file pointer
     * @throws IOException if an I/O error occurs
     */
    long getFilePointer() throws IOException {
        return randomAccessFile.getFilePointer();
    }

    /**
     * Writes a segment of bytes into the file.
     * @param b byte array containing bytes to write into the file
     * @param off starting position of segment
     * @param len number of bytes to be written
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    void write(byte[] b, int off, int len)
                                    throws IOException, StandardException {
            randomAccessFile.write (b, off, len);
    }

    /**
     * Reads one byte from file.
     * @return byte
     * @throws IOException if disk operation fails
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    int readByte() throws IOException, StandardException {
        return randomAccessFile.readByte();
    }

    /**
     * Reads len number of bytes from the file starting from off position
     * in the buffer.
     * @param buff buffer
     * @param off starting position of buffer
     * @param len number of bytes
     * @return number of bytes read
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    int read(byte[] buff, int off, int len)
                                    throws IOException, StandardException {
        return randomAccessFile.read (buff, off, len);
    }

    /**
     * Closes the file.
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    void close() throws IOException {
        randomAccessFile.close();
    }

    /**
     * Sets the file length to a given size.
     * @param size new size
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    void setLength(long size) throws IOException, StandardException {
        randomAccessFile.setLength (size);
    }

    /**
     * Writes a buffer completely into the file.
     * @param buf buffer to write
     * @throws IOException if an I/O error occurs
     * @throws StandardException it won't be thrown, it's in signature to allow
     *              subclasses to throw StandardException
     */
    void write(byte[] buf) throws IOException, StandardException {
        randomAccessFile.write (buf);
    }

}