inflaterinputstream.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 353 行

/*
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.util.zip;

import java.io.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;

import sun.io.Markable;
import sun.io.MarkableReader;

/**
 * This class implements a stream filter for uncompressing data in the
 * "deflate" compression format. It is also used as the basis for other
 * decompression filters, such as GZIPInputStream.
 * NOTE: <B>java.util.zip.GZIPInputStream</B> is found in J2ME CDC profiles 
 * such as J2ME Foundation Profile.
 *
 * @see        Inflater
 * @version     1.28, 02/02/00
 * @author     David Connelly
 */
public
class InflaterInputStream extends FilterInputStream {
    /**
     * Decompressor for this stream.
     */
    protected Inflater inf;

    /**
     * Input buffer for decompression.
     */
    protected byte[] buf;

    /**
     * Length of input buffer.
     */
    protected int len;

    private boolean closed = false;
    // this flag is set to true after EOF has reached
    private boolean reachEOF = false;
    
    private MarkableReader reader;
    
    /**
     * Check to make sure that this stream has not been closed
     */
    private void ensureOpen() throws IOException {
        if (closed) {
            throw new IOException("Stream closed");
        }
    }


    /**
     * Creates a new input stream with the specified decompressor and
     * buffer size.
     * @param in the input stream
     * @param inf the decompressor ("inflater")
     * @param size the input buffer size
     * @exception IllegalArgumentException if size is <= 0
     */
    public InflaterInputStream(InputStream in, Inflater inf, int size) {
        super(in);
        if (in == null || inf == null) {
            throw new NullPointerException();
        } else if (size <= 0) {
            throw new IllegalArgumentException("buffer size <= 0");
        }
        this.inf = inf;
        reader = new MarkableReader(new NativeReader());
        buf = new byte[size];
    }

    /**
     * Creates a new input stream with the specified decompressor and a
     * default buffer size.
     * @param in the input stream
     * @param inf the decompressor ("inflater")
     */
    public InflaterInputStream(InputStream in, Inflater inf) {
        this(in, inf, 512);
    }

    boolean usesDefaultInflater = false;

    /**
     * Creates a new input stream with a default decompressor and buffer size.
     * @param in the input stream
     */
    public InflaterInputStream(InputStream in) {
        this(in, new Inflater());
        usesDefaultInflater = true;
    }

    private byte[] singleByteBuf = new byte[1];

    /**
     * Reads a byte of uncompressed data. This method will block until
     * enough input is available for decompression.
     * @return the byte read, or -1 if end of compressed input is reached
     * @exception IOException if an I/O error has occurred
     */
    public int read() throws IOException {
        ensureOpen();
        return read(singleByteBuf, 0, 1) == -1 ? -1 : singleByteBuf[0] & 0xff;
    }

    /**
     * Reads uncompressed data into an array of bytes. This method will
     * block until some input can be decompressed.
     * @param b the buffer into which the data is read
     * @param off the start offset of the data
     * @param len the maximum number of bytes read
     * @return the actual number of bytes read, or -1 if the end of the
     *         compressed input is reached or a preset dictionary is needed
     * @exception ZipException if a ZIP format error has occurred
     * @exception IOException if an I/O error has occurred
     */
     
    public int read(byte[] b, int off, int len)  throws IOException {
        return reader.read(b, off, len);
    }

    private class NativeReader implements Markable {

        public int readNative(byte[] b, int off, int len) throws IOException {
            ensureOpen();
            try {
                int bytesRead = 0;
                while (len > 0) {
                    int n = inf.inflate(b, off, len);
                    if (n == 0) {
                        if (inf.finished() || inf.needsDictionary()) {
                            reachEOF = true;
                            if (bytesRead > 0) {
                                return bytesRead;
                            } else {
                                return -1;
                            }
                        }
                        if (inf.needsInput()) {
                            fill();
                        }
                    }
                    bytesRead += n;
                    off += n;
                    len -= n;
                }
                return bytesRead;
            } catch (DataFormatException e) {
                String s = e.getMessage();
                throw new ZipException(s != null ? s : "Invalid ZLIB data format");
            }
        }
    }
    /**
     * Returns 0 after EOF has reached, otherwise always return 1.
     * <p>
     * Programs should not count on this method to return the actual number
     * of bytes that could be read without blocking.
     *
     * @return     1 before EOF and 0 after EOF.
     * @exception  IOException  if an I/O error occurs.
     * 
     */
    public int available() throws IOException {
        ensureOpen();
        if (reachEOF) {
            return 0;
        } else {
            return 1;
        }
    }

    private byte[] b = new byte[512];

    /**
     * Skips specified number of bytes of uncompressed data.
     * @param n the number of bytes to skip
     * @return the actual number of bytes skipped.
     * @exception IOException if an I/O error has occurred
     * @exception IllegalArgumentException if n < 0
     */
    public long skip(long n) throws IOException {
        if (n < 0) {
            throw new IllegalArgumentException("negative skip length");
        }
        ensureOpen();
        int max = (int)Math.min(n, Integer.MAX_VALUE);
        int total = 0;
        while (total < max) {
            int len = max - total;
            if (len > b.length) {
                len = b.length;
            }
            len = read(b, 0, len);
            if (len == -1) {
                reachEOF = true;
                break;
            }
            total += len;
        }
        return total;
    }

    /**
     * Closes the input stream.
     * @exception IOException if an I/O error has occurred
     */
    public void close() throws IOException {
        if (!closed) {
            if (usesDefaultInflater)
                inf.end();
            in.close();
            closed = true;
        }
    }

    /**
     * Fills input buffer with more data to decompress.
     * @exception IOException if an I/O error has occurred
     */
    protected void fill() throws IOException {
        ensureOpen();
        len = in.read(buf, 0, buf.length);
        if (len == -1) {
            throw new EOFException("Unexpected end of ZLIB input stream");
        }
        inf.setInput(buf, 0, len);
    }
    
    /**
     * Marks the current position in this input stream. A subsequent call to
     * the <code>reset</code> method repositions this stream at the last marked
     * position so that subsequent reads re-read the same bytes.
     *
     * <p> The <code>readlimit</code> arguments tells this input stream to
     * allow that many bytes to be read before the mark position gets
     * invalidated.
     *
     * <p> The general contract of <code>mark</code> is that, if the method
     * <code>markSupported</code> returns <code>true</code>, the stream somehow
     * remembers all the bytes read after the call to <code>mark</code> and
     * stands ready to supply those same bytes again if and whenever the method
     * <code>reset</code> is called.  However, the stream is not required to
     * remember any data at all if more than <code>readlimit</code> bytes are
     * read from the stream before <code>reset</code> is called.
     *
     * <p> The <code>mark</code> method of <code>InputStream</code> does
     * nothing.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     java.io.InputStream#reset()
     */
    public synchronized void mark(int readlimit) {
        reader.mark(readlimit);
    }

    /**
     * Repositions this stream to the position at the time the
     * <code>mark</code> method was last called on this input stream.
     *
     * <p> The general contract of <code>reset</code> is:
     *
     * <p><ul>
     *
     * <li> If the method <code>markSupported</code> returns
     * <code>true</code>, then:
     *
     *     <ul><li> If the method <code>mark</code> has not been called since
     *     the stream was created, or the number of bytes read from the stream
     *     since <code>mark</code> was last called is larger than the argument
     *     to <code>mark</code> at that last call, then an
     *     <code>IOException</code> might be thrown.
     *
     *     <li> If such an <code>IOException</code> is not thrown, then the
     *     stream is reset to a state such that all the bytes read since the
     *     most recent call to <code>mark</code> (or since the start of the
     *     file, if <code>mark</code> has not been called) will be resupplied
     *     to subsequent callers of the <code>read</code> method, followed by
     *     any bytes that otherwise would have been the next input data as of
     *     the time of the call to <code>reset</code>. </ul>
     *
     * <li> If the method <code>markSupported</code> returns
     * <code>false</code>, then:
     *
     *     <ul><li> The call to <code>reset</code> may throw an
     *     <code>IOException</code>.
     *
     *     <li> If an <code>IOException</code> is not thrown, then the stream
     *     is reset to a fixed state that depends on the particular type of the
     *     input stream and how it was created. The bytes that will be supplied
     *     to subsequent callers of the <code>read</code> method depend on the
     *     particular type of the input stream. </ul></ul>
     *
     * <p> The method <code>reset</code> for class <code>InputStream</code>
     * does nothing and always throws an <code>IOException</code>.
     *
     * @exception  IOException  if this stream has not been marked or if the
     *               mark has been invalidated.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.IOException
     */
    public synchronized void reset() throws IOException {
        reader.reset();
    }

    /**
     * Tests if this input stream supports the <code>mark</code> and
     * <code>reset</code> methods. Whether or not <code>mark</code> and
     * <code>reset</code> are supported is an invariant property of a
     * particular input stream instance. The <code>markSupported</code> method
     * of <code>InputStream</code> returns <code>false</code>.
     *
     * @return  <code>true</code> if this stream instance supports the mark
     *          and reset methods; <code>false</code> otherwise.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    public boolean markSupported() {
       return reader.markSupported();
    }

}