/*
 * @(#)DeflaterInputStream.java	1.1 06/01/30
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util.zip;

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

/**
 * Implements an input stream filter for compressing data in the "deflate"
 * compression format.
 *
 * @version	1.1
 * @since	1.6
 * @author	David R Tribble (david@tribble.com)
 *
 * @see	DeflaterOutputStream
 * @see	InflaterOutputStream
 * @see	InflaterInputStream
 */

public class DeflaterInputStream extends FilterInputStream {
    /** Compressor for this stream. */
    protected final Deflater def;

    /** Input buffer for reading compressed data. */
    protected final byte[] buf;

    /** Temporary read buffer. */
    private byte[] rbuf = new byte[1];

    /** Default compressor is used. */
    private boolean usesDefaultDeflater = false;

    /** End of the underlying input stream has been reached. */
    private boolean reachEOF = false;

    /**
     * Check to make sure that this stream has not been closed.
     */
    private void ensureOpen() throws IOException {
        if (in == null) {
            throw new IOException("Stream closed");
        }
    }

    /**
     * Creates a new input stream with a default compressor and buffer
     * size.
     *
     * @param in input stream to read the uncompressed data to
     * @throws NullPointerException if {@code in} is null
     */
    public DeflaterInputStream(InputStream in) {
        this(in, new Deflater());
        usesDefaultDeflater = true;
    }

    /**
     * Creates a new input stream with the specified compressor and a
     * default buffer size.
     *
     * @param in input stream to read the uncompressed data to
     * @param defl compressor ("deflater") for this stream
     * @throws NullPointerException if {@code in} or {@code defl} is null
     */
    public DeflaterInputStream(InputStream in, Deflater defl) {
        this(in, defl, 512);
    }

    /**
     * Creates a new input stream with the specified compressor and buffer
     * size.
     *
     * @param in input stream to read the uncompressed data to
     * @param defl compressor ("deflater") for this stream
     * @param bufLen compression buffer size
     * @throws IllegalArgumentException if {@code bufLen} is <= 0
     * @throws NullPointerException if {@code in} or {@code defl} is null
     */
    public DeflaterInputStream(InputStream in, Deflater defl, int bufLen) {
        super(in);

        // Sanity checks
        if (in == null)
            throw new NullPointerException("Null input");
        if (defl == null)
            throw new NullPointerException("Null deflater");
        if (bufLen < 1)
            throw new IllegalArgumentException("Buffer size < 1");

        // Initialize
        def = defl;
        buf = new byte[bufLen];
    }

    /**
     * Closes this input stream and its underlying input stream, discarding
     * any pending uncompressed data.
     *
     * @throws IOException if an I/O error occurs
     */
    public void close() throws IOException {
        if (in != null) {
            try {
                // Clean up
                if (usesDefaultDeflater) {
                    def.end();
                }

                in.close();
            } finally {
                in = null;
            }
        }
    }

    /**
     * Reads a single byte of compressed data from the input stream.
     * This method will block until some input can be read and compressed.
     *
     * @return a single byte of compressed data, or -1 if the end of the
     * uncompressed input stream is reached
     * @throws IOException if an I/O error occurs or if this stream is
     * already closed
     */
    public int read() throws IOException {
        // Read a single byte of compressed data
        int len = read(rbuf, 0, 1);
        if (len <= 0)
            return -1;
        return (rbuf[0] & 0xFF);
    }

    /**
     * Reads compressed data into a byte array.
     * This method will block until some input can be read and compressed.
     *
     * @param b buffer into which the data is read
     * @param off starting offset of the data within {@code b}
     * @param len maximum number of compressed bytes to read into {@code b}
     * @return the actual number of bytes read, or -1 if the end of the
     * uncompressed input stream is reached
     * @throws IndexOutOfBoundsException  if {@code len} > {@code b.length -
     * off}
     * @throws IOException if an I/O error occurs or if this input stream is
     * already closed
     */
    public int read(byte[] b, int off, int len) throws IOException {
        // Sanity checks
        ensureOpen();
        if (b == null) {
            throw new NullPointerException("Null buffer for read");
        } else if (off < 0 || len < 0 || len > b.length - off) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return 0;
        }

        // Read and compress (deflate) input data bytes
        int cnt = 0;
        while (len > 0 && !def.finished()) {
            int n;

            // Read data from the input stream
            if (def.needsInput()) {
                n = in.read(buf, 0, buf.length);
                if (n < 0) {
                    // End of the input stream reached
                    def.finish();
                } else if (n > 0) {
                    def.setInput(buf, 0, n);
                }
            }

            // Compress the input data, filling the read buffer
            n = def.deflate(b, off, len);
            cnt += n;
            off += n;
            len -= n;
        }
        if (cnt == 0 && def.finished()) {
            reachEOF = true;
            cnt = -1;
        }

        return cnt;
    }

    /**
     * Skips over and discards data from the input stream.
     * This method may block until the specified number of bytes are read and
     * skipped. <em>Note:</em> While {@code n} is given as a {@code long},
     * the maximum number of bytes which can be skipped is
     * {@code Integer.MAX_VALUE}.
     *
     * @param n number of bytes to be skipped
     * @return the actual number of bytes skipped
     * @throws IOException if an I/O error occurs or if this stream is
     * already closed
     */
    public long skip(long n) throws IOException {
        if (n < 0) {
            throw new IllegalArgumentException("negative skip length");
        }
        ensureOpen();

        // Skip bytes by repeatedly decompressing small blocks
        if (rbuf.length < 512)
            rbuf = new byte[512];

        int total = (int)Math.min(n, Integer.MAX_VALUE);
        long cnt = 0;
        while (total > 0) {
            // Read a small block of uncompressed bytes
            int len = read(rbuf, 0, (total <= rbuf.length ? total : rbuf.length));

            if (len < 0) {
                break;
            }
            cnt += len;
            total -= len;
        }
        return cnt;
    }

    /**
     * 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 zero after the end of the underlying input stream has been
     * reached, otherwise always returns 1
     * @throws IOException if an I/O error occurs or if this stream is
     * already closed
     */
    public int available() throws IOException {
        ensureOpen();
        if (reachEOF) {
            return 0;
        }
        return 1;
    }

    /**
     * Always returns {@code false} because this input stream does not support
     * the {@link #mark mark()} and {@link #reset reset()} methods.
     *
     * @return false, always
     */
    public boolean markSupported() {
        return false;
    }

    /**
     * <i>This operation is not supported</i>.
     *
     * @param limit maximum bytes that can be read before invalidating the position marker
     */
    public void mark(int limit) {
        // Operation not supported
    }

    /**
     * <i>This operation is not supported</i>.
     *
     * @throws IOException always thrown
     */
    public void reset() throws IOException {
        throw new IOException("mark/reset not supported");
    }
}
