trunk/odfdom/src/main/java/org/odftoolkit/odfdom/pkg/StreamHelper.java

/************************************************************************
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 *
 * Copyright 2008, 2010 Oracle and/or its affiliates. All rights reserved.
 *
 * Use is subject to license terms.
 *
 * 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. You can also
 * obtain a copy of the License at http://odftoolkit.org/docs/license.txt
 *
 * 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.odftoolkit.odfdom.pkg;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * This class reads from an InputStream and writes to an OutputStream.
 * No streams will be closed - calling classes must do this.
 */
class StreamHelper {

    // 4096 is thought to be the minimum page size for most systems;
    // change this for optimization
    public static final int PAGE_SIZE = 4096;
    private InputStream in;
    private OutputStream out;
    private boolean mStreamed;

    /**
     * Read from the input stream and write to the output. This method
     * does not close any stream; calling methods must take care of that.
     * @throws IOException when io error happens
     */
    static void transformStream(InputStream in, OutputStream out) throws IOException {
        StreamHelper s = new StreamHelper(in, out);
        s.stream();
    }

    /**
     * Create a new StreamHelper
     * @param in the input stream used for reading
     * @param out the output stream written to
     */
    StreamHelper(InputStream in, OutputStream out) {
        this.in = in;
        this.out = out;
        mStreamed = false;
    }

    /**
     * Read from the input stream and write to the output. This method can only
     * be called once. A second call will result in an IOException. This method
     * does not close any stream; calling methods must take care of that.
     * @throws IOException when io error happens
     */
    void stream() throws IOException {
        if (mStreamed) throw new IOException();
        byte[] buf = new byte[PAGE_SIZE];
        int r = 0;
        // let npe happen if one of the streams is null
        while ((r = in.read(buf, 0, PAGE_SIZE)) > -1) {
            out.write(buf, 0, r);
        }
        // free the references
        in = null;
        out = null;
        mStreamed = true;
    }
}