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package java.util.zip;

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

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.
Author:
     David Connelly
See Also:
Inflater
Since:
1.1/**
 * 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.
 *
 * @see         Inflater
 * @author      David Connelly
 * @since 1.1
 */
public
class InflaterInputStream extends FilterInputStream {
    
Decompressor for this stream.
/**
     * Decompressor for this stream.
     */
    protected Inflater inf;

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

    
Length of input buffer.
/**
     * 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;

    
Check to make sure that this stream has not been closed
/**
     * 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.
Params:
in – the input stream
inf – the decompressor ("inflater")
size – the input buffer size
Throws:
IllegalArgumentException – if size <= 0/**
     * 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 {@code size <= 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;
        buf = new byte[size];
    }

    
Creates a new input stream with the specified decompressor and a
default buffer size.
Params:
in – the input stream
inf – the decompressor ("inflater")/**
     * 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.
Params:
in – the input stream/**
     * 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.
Throws:
IOException – if an I/O error has occurred
Returns:
the byte read, or -1 if end of compressed input is reached/**
     * 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 : Byte.toUnsignedInt(singleByteBuf[0]);
    }

    
Reads uncompressed data into an array of bytes. If len is not
zero, the method will block until some input can be decompressed; otherwise,
no bytes are read and 0 is returned.
Params:
b – the buffer into which the data is read
off – the start offset in the destination array b
len – the maximum number of bytes read
Throws:
NullPointerException – If b is null.
IndexOutOfBoundsException – If off is negative,
len is negative, or len is greater than
b.length - off
ZipException – if a ZIP format error has occurred
IOException – if an I/O error has occurred
Returns:
the actual number of bytes read, or -1 if the end of the
        compressed input is reached or a preset dictionary is needed/**
     * Reads uncompressed data into an array of bytes. If <code>len</code> is not
     * zero, the method will block until some input can be decompressed; otherwise,
     * no bytes are read and <code>0</code> is returned.
     * @param b the buffer into which the data is read
     * @param off the start offset in the destination array <code>b</code>
     * @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  NullPointerException If <code>b</code> is <code>null</code>.
     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
     * <code>len</code> is negative, or <code>len</code> is greater than
     * <code>b.length - off</code>
     * @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 {
        ensureOpen();
        if (b == null) {
            throw new NullPointerException();
        } else if (off < 0 || len < 0 || len > b.length - off) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return 0;
        }
        try {
            int n;
            while ((n = inf.inflate(b, off, len)) == 0) {
                if (inf.finished() || inf.needsDictionary()) {
                    reachEOF = true;
                    return -1;
                }
                if (inf.needsInput()) {
                    fill();
                }
            }
            return n;
        } catch (DataFormatException e) {
            String s = e.getMessage();
            throw new ZipException(s != null ? s : "Invalid ZLIB data format");
        }
    }

    
Returns 0 after EOF has been reached, otherwise always return 1.

Programs should not count on this method to return the actual number
of bytes that could be read without blocking.
Throws:
IOException –  if an I/O error occurs.
Returns:
    1 before EOF and 0 after EOF./**
     * Returns 0 after EOF has been 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 if (inf.finished()) {
            // the end of the compressed data stream has been reached
            reachEOF = true;
            return 0;
        } else {
            return 1;
        }
    }

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

    
Skips specified number of bytes of uncompressed data.
Params:
n – the number of bytes to skip
Throws:
IOException – if an I/O error has occurred
IllegalArgumentException – if n < 0
Returns:
the actual number of bytes skipped./**
     * 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 {@code 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 this input stream and releases any system resources associated
with the stream.
Throws:
IOException – if an I/O error has occurred/**
     * Closes this input stream and releases any system resources associated
     * with the 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.
Throws:
IOException – if an I/O error has occurred/**
     * 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);
    }

    
Tests if this input stream supports the mark and
reset methods. The markSupported
method of InflaterInputStream returns
false.
See Also:
InputStream.mark(int)
InputStream.reset()
Returns:
 a boolean indicating if this stream type supports
         the mark and reset methods./**
     * Tests if this input stream supports the <code>mark</code> and
     * <code>reset</code> methods. The <code>markSupported</code>
     * method of <code>InflaterInputStream</code> returns
     * <code>false</code>.
     *
     * @return  a <code>boolean</code> indicating if this stream type supports
     *          the <code>mark</code> and <code>reset</code> methods.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    public boolean markSupported() {
        return false;
    }

    
Marks the current position in this input stream.
 The mark method of InflaterInputStream
does nothing.
Params:
readlimit –   the maximum limit of bytes that can be read before
                     the mark position becomes invalid.
See Also:
InputStream.reset()/**
     * Marks the current position in this input stream.
     *
     * <p> The <code>mark</code> method of <code>InflaterInputStream</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) {
    }

    
Repositions this stream to the position at the time the
mark method was last called on this input stream.
 The method reset for class
InflaterInputStream does nothing except throw an
IOException.
Throws:
IOException –  if this method is invoked.
See Also:
InputStream.mark(int)
IOException/**
     * Repositions this stream to the position at the time the
     * <code>mark</code> method was last called on this input stream.
     *
     * <p> The method <code>reset</code> for class
     * <code>InflaterInputStream</code> does nothing except throw an
     * <code>IOException</code>.
     *
     * @exception  IOException  if this method is invoked.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.IOException
     */
    public synchronized void reset() throws IOException {
        throw new IOException("mark/reset not supported");
    }
}