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TrueZIP is a Java based Virtual File System (VFS) to enable transparent, multi-threaded read/write access to archive files (ZIP, TAR etc.) as if they were directories. Archive files may be arbitrarily nested and the nesting level is only limited by heap and file system size.

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/*
 * Copyright (C) 2005-2010 Schlichtherle IT Services
 *
 * 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
 *
 * 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 de.schlichtherle.io.rof;

import java.io.IOException;

/**
 * A minimal interface to allow random read only access to a file.
 * This interface is required by the class {@link java.util.zip.ZipFile} to
 * read a ZIP compatible file which may or may not be encrypted.
 *
 * @author Christian Schlichtherle
 * @version $Id: ReadOnlyFile.java,v 1.4 2010/08/20 13:09:47 christian_schlichtherle Exp $
 */
public interface ReadOnlyFile {

    long length() throws IOException;

    long getFilePointer() throws IOException;

    /**
     * Sets the file pointer offset, measured from the beginning of this 
     * file, at which the next read occurs.
     * Whether the offset may be set beyond the end of the file is up to
     * the implementor.
     * For example, the {@link SimpleReadOnlyFile} subclasses
     * {@link java.io.RandomAccessFile} and passes {@code "r"} as a
     * parameter to the superclass constructor.
     * On the Windows platform, this implementation allows to seek past the
     * end of file, but on the Linux platform it doesn't.
     *
     * @param pos The offset position, measured in bytes from the beginning
     *        of the file, at which to set the file pointer.
     * @throws IOException If {@code pos} is less than {@code 0} or if
     *         an I/O error occurs.
     */
    void seek(long pos) throws IOException;

    int read() throws IOException;

    int read(byte[] b) throws IOException;

    /**
     * Reads up to {@code len} bytes of data from this read only file into
     * the given array.
     * This method blocks until at least one byte of input is available.
     *
     * @param b The buffer to fill with data.
     * @param off The start offset of the data.
     * @param len The maximum number of bytes to read.
     *
     * @return The total number of bytes read, or {@code -1} if there is
     *         no more data because the end of the file has been reached.
     *
     * @throws IOException On any I/O related issue.
     */
    int read(byte[] b, int off, int len) throws IOException;

    void readFully(byte[] b) throws IOException;

    void readFully(byte[] b, int off, int len) throws IOException;

    /** @deprecated Use {@link #seek} instead. */
    int skipBytes(int n) throws IOException;

    void close() throws IOException;
}