/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.jvnet.mimepull;

import java.nio.ByteBuffer;

Keeps the Part's partial content data in a file.
Author:
Kohsuke Kawaguchi, Jitendra Kotamraju/**
 * Keeps the Part's partial content data in a file.
 *
 * @author Kohsuke Kawaguchi
 * @author Jitendra Kotamraju
 */
final class FileData implements Data {
    private final DataFile file;
    private final long pointer;         // read position
    private final int length;

    FileData(DataFile file, ByteBuffer buf) {
        this(file, file.writeTo(buf.array(), 0, buf.limit()), buf.limit());
    }

    FileData(DataFile file, long pointer, int length) {
        this.file = file;
        this.pointer = pointer;
        this.length = length;
    }

    @Override
    public byte[] read() {
        byte[] buf = new byte[length];
        file.read(pointer, buf, 0, length);
        return buf;
    }

    /*
     * This shouldn't be called
     */
    @Override
    public long writeTo(DataFile file) {
        throw new IllegalStateException();
    }

    @Override
    public int size() {
        return length;
    }

    /*
     * Always create FileData
     */
    @Override
    public Data createNext(DataHead dataHead, ByteBuffer buf) {
        return new FileData(file, buf);
    }
}