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/*
 * Copyright (c) 2000, 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 in the LICENSE file that
 * accompanied this code).
 *
 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.imageio.stream;

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteOrder;
import java.util.Stack;
import javax.imageio.IIOException;


An abstract class implementing the ImageInputStream interface.
This class is designed to reduce the number of methods that must
be implemented by subclasses.

 In particular, this class handles most or all of the details of
byte order interpretation, buffering, mark/reset, discarding,
closing, and disposing.

/**
 * An abstract class implementing the <code>ImageInputStream</code> interface.
 * This class is designed to reduce the number of methods that must
 * be implemented by subclasses.
 *
 * <p> In particular, this class handles most or all of the details of
 * byte order interpretation, buffering, mark/reset, discarding,
 * closing, and disposing.
 */
public abstract class ImageInputStreamImpl implements ImageInputStream {

    private Stack markByteStack = new Stack();

    private Stack markBitStack = new Stack();

    private boolean isClosed = false;

    // Length of the buffer used for readFully(type[], int, int)
    private static final int BYTE_BUF_LENGTH = 8192;

    
Byte buffer used for readFully(type[], int, int).  Note that this
array is also used for bulk reads in readShort(), readInt(), etc, so
it should be large enough to hold a primitive value (i.e. >= 8 bytes).
Also note that this array is package protected, so that it can be
used by ImageOutputStreamImpl in a similar manner.

/**
     * Byte buffer used for readFully(type[], int, int).  Note that this
     * array is also used for bulk reads in readShort(), readInt(), etc, so
     * it should be large enough to hold a primitive value (i.e. >= 8 bytes).
     * Also note that this array is package protected, so that it can be
     * used by ImageOutputStreamImpl in a similar manner.
     */
    byte[] byteBuf = new byte[BYTE_BUF_LENGTH];

    
The byte order of the stream as an instance of the enumeration
class java.nio.ByteOrder, where
ByteOrder.BIG_ENDIAN indicates network byte order
and ByteOrder.LITTLE_ENDIAN indicates the reverse
order.  By default, the value is
ByteOrder.BIG_ENDIAN.

/**
     * The byte order of the stream as an instance of the enumeration
     * class <code>java.nio.ByteOrder</code>, where
     * <code>ByteOrder.BIG_ENDIAN</code> indicates network byte order
     * and <code>ByteOrder.LITTLE_ENDIAN</code> indicates the reverse
     * order.  By default, the value is
     * <code>ByteOrder.BIG_ENDIAN</code>.
     */
    protected ByteOrder byteOrder = ByteOrder.BIG_ENDIAN;

    
The current read position within the stream.  Subclasses are
responsible for keeping this value current from any method they
override that alters the read position.

/**
     * The current read position within the stream.  Subclasses are
     * responsible for keeping this value current from any method they
     * override that alters the read position.
     */
    protected long streamPos;

    
The current bit offset within the stream.  Subclasses are
responsible for keeping this value current from any method they
override that alters the bit offset.

/**
     * The current bit offset within the stream.  Subclasses are
     * responsible for keeping this value current from any method they
     * override that alters the bit offset.
     */
    protected int bitOffset;

    
The position prior to which data may be discarded.  Seeking
to a smaller position is not allowed.  flushedPos
will always be >= 0.

/**
     * The position prior to which data may be discarded.  Seeking
     * to a smaller position is not allowed.  <code>flushedPos</code>
     * will always be >= 0.
     */
    protected long flushedPos = 0;

    
Constructs an ImageInputStreamImpl.

/**
     * Constructs an <code>ImageInputStreamImpl</code>.
     */
    public ImageInputStreamImpl() {
    }

    
Throws an IOException if the stream has been closed.
Subclasses may call this method from any of their methods that
require the stream not to be closed.

Throws:
  • IOException – if the stream is closed.
/**
     * Throws an <code>IOException</code> if the stream has been closed.
     * Subclasses may call this method from any of their methods that
     * require the stream not to be closed.
     *
     * @exception IOException if the stream is closed.
     */
    protected final void checkClosed() throws IOException {
        if (isClosed) {
            throw new IOException("closed");
        }
    }

    public void setByteOrder(ByteOrder byteOrder) {
        this.byteOrder = byteOrder;
    }

    public ByteOrder getByteOrder() {
        return byteOrder;
    }

    
Reads a single byte from the stream and returns it as an
int between 0 and 255.  If EOF is reached,
-1 is returned.

 Subclasses must provide an implementation for this method.
The subclass implementation should update the stream position
before exiting.

 The bit offset within the stream must be reset to zero before
the read occurs.

Throws:
Returns:the value of the next byte in the stream, or -1
if EOF is reached.
/**
     * Reads a single byte from the stream and returns it as an
     * <code>int</code> between 0 and 255.  If EOF is reached,
     * <code>-1</code> is returned.
     *
     * <p> Subclasses must provide an implementation for this method.
     * The subclass implementation should update the stream position
     * before exiting.
     *
     * <p> The bit offset within the stream must be reset to zero before
     * the read occurs.
     *
     * @return the value of the next byte in the stream, or <code>-1</code>
     * if EOF is reached.
     *
     * @exception IOException if the stream has been closed.
     */
    public abstract int read() throws IOException;

    
A convenience method that calls read(b, 0, b.length).

 The bit offset within the stream is reset to zero before
the read occurs.

Throws:
Returns:the number of bytes actually read, or -1
to indicate EOF.
/**
     * A convenience method that calls <code>read(b, 0, b.length)</code>.
     *
     * <p> The bit offset within the stream is reset to zero before
     * the read occurs.
     *
     * @return the number of bytes actually read, or <code>-1</code>
     * to indicate EOF.
     *
     * @exception NullPointerException if <code>b</code> is
     * <code>null</code>.
     * @exception IOException if an I/O error occurs.
     */
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    
Reads up to len bytes from the stream, and stores
them into b starting at index off.
If no bytes can be read because the end of the stream has been
reached, -1 is returned.

 The bit offset within the stream must be reset to zero before
the read occurs.

 Subclasses must provide an implementation for this method.
The subclass implementation should update the stream position
before exiting.

Params:
  • b – an array of bytes to be written to.
  • off – the starting position within b to write to.
  • len – the maximum number of bytes to read.
Throws:
Returns:the number of bytes actually read, or -1
to indicate EOF.
/**
     * Reads up to <code>len</code> bytes from the stream, and stores
     * them into <code>b</code> starting at index <code>off</code>.
     * If no bytes can be read because the end of the stream has been
     * reached, <code>-1</code> is returned.
     *
     * <p> The bit offset within the stream must be reset to zero before
     * the read occurs.
     *
     * <p> Subclasses must provide an implementation for this method.
     * The subclass implementation should update the stream position
     * before exiting.
     *
     * @param b an array of bytes to be written to.
     * @param off the starting position within <code>b</code> to write to.
     * @param len the maximum number of bytes to read.
     *
     * @return the number of bytes actually read, or <code>-1</code>
     * to indicate EOF.
     *
     * @exception IndexOutOfBoundsException if <code>off</code> is
     * negative, <code>len</code> is negative, or <code>off +
     * len</code> is greater than <code>b.length</code>.
     * @exception NullPointerException if <code>b</code> is
     * <code>null</code>.
     * @exception IOException if an I/O error occurs.
     */
    public abstract int read(byte[] b, int off, int len) throws IOException;

    public void readBytes(IIOByteBuffer buf, int len) throws IOException {
        if (len < 0) {
            throw new IndexOutOfBoundsException("len < 0!");
        }
        if (buf == null) {
            throw new NullPointerException("buf == null!");
        }

        byte[] data = new byte[len];
        len = read(data, 0, len);

        buf.setData(data);
        buf.setOffset(0);
        buf.setLength(len);
    }

    public boolean readBoolean() throws IOException {
        int ch = this.read();
        if (ch < 0) {
            throw new EOFException();
        }
        return (ch != 0);
    }

    public byte readByte() throws IOException {
        int ch = this.read();
        if (ch < 0) {
            throw new EOFException();
        }
        return (byte)ch;
    }

    public int readUnsignedByte() throws IOException {
        int ch = this.read();
        if (ch < 0) {
            throw new EOFException();
        }
        return ch;
    }

    public short readShort() throws IOException {
        if (read(byteBuf, 0, 2) < 0) {
            throw new EOFException();
        }

        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            return (short)
                (((byteBuf[0] & 0xff) << 8) | ((byteBuf[1] & 0xff) << 0));
        } else {
            return (short)
                (((byteBuf[1] & 0xff) << 8) | ((byteBuf[0] & 0xff) << 0));
        }
    }

    public int readUnsignedShort() throws IOException {
        return ((int)readShort()) & 0xffff;
    }

    public char readChar() throws IOException {
        return (char)readShort();
    }

    public int readInt() throws IOException {
        if (read(byteBuf, 0, 4) < 0) {
            throw new EOFException();
        }

        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            return
                (((byteBuf[0] & 0xff) << 24) | ((byteBuf[1] & 0xff) << 16) |
                 ((byteBuf[2] & 0xff) <<  8) | ((byteBuf[3] & 0xff) <<  0));
        } else {
            return
                (((byteBuf[3] & 0xff) << 24) | ((byteBuf[2] & 0xff) << 16) |
                 ((byteBuf[1] & 0xff) <<  8) | ((byteBuf[0] & 0xff) <<  0));
        }
    }

    public long readUnsignedInt() throws IOException {
        return ((long)readInt()) & 0xffffffffL;
    }

    public long readLong() throws IOException {
        // REMIND: Once 6277756 is fixed, we should do a bulk read of all 8
        // bytes here as we do in readShort() and readInt() for even better
        // performance (see 6347575 for details).
        int i1 = readInt();
        int i2 = readInt();

        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            return ((long)i1 << 32) + (i2 & 0xFFFFFFFFL);
        } else {
            return ((long)i2 << 32) + (i1 & 0xFFFFFFFFL);
        }
    }

    public float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    public double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    public String readLine() throws IOException {
        StringBuffer input = new StringBuffer();
        int c = -1;
        boolean eol = false;

        while (!eol) {
            switch (c = read()) {
            case -1:
            case '\n':
                eol = true;
                break;
            case '\r':
                eol = true;
                long cur = getStreamPosition();
                if ((read()) != '\n') {
                    seek(cur);
                }
                break;
            default:
                input.append((char)c);
                break;
            }
        }

        if ((c == -1) && (input.length() == 0)) {
            return null;
        }
        return input.toString();
    }

    public String readUTF() throws IOException {
        this.bitOffset = 0;

        // Fix 4494369: method ImageInputStreamImpl.readUTF()
        // does not work as specified (it should always assume
        // network byte order).
        ByteOrder oldByteOrder = getByteOrder();
        setByteOrder(ByteOrder.BIG_ENDIAN);

        String ret;
        try {
            ret = DataInputStream.readUTF(this);
        } catch (IOException e) {
            // Restore the old byte order even if an exception occurs
            setByteOrder(oldByteOrder);
            throw e;
        }

        setByteOrder(oldByteOrder);
        return ret;
    }

    public void readFully(byte[] b, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > b.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > b.length!");
        }

        while (len > 0) {
            int nbytes = read(b, off, len);
            if (nbytes == -1) {
                throw new EOFException();
            }
            off += nbytes;
            len -= nbytes;
        }
    }

    public void readFully(byte[] b) throws IOException {
        readFully(b, 0, b.length);
    }

    public void readFully(short[] s, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > s.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > s.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/2);
            readFully(byteBuf, 0, nelts*2);
            toShorts(byteBuf, s, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    public void readFully(char[] c, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > c.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > c.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/2);
            readFully(byteBuf, 0, nelts*2);
            toChars(byteBuf, c, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    public void readFully(int[] i, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > i.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > i.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/4);
            readFully(byteBuf, 0, nelts*4);
            toInts(byteBuf, i, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    public void readFully(long[] l, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > l.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > l.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/8);
            readFully(byteBuf, 0, nelts*8);
            toLongs(byteBuf, l, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    public void readFully(float[] f, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > f.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > f.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/4);
            readFully(byteBuf, 0, nelts*4);
            toFloats(byteBuf, f, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    public void readFully(double[] d, int off, int len) throws IOException {
        // Fix 4430357 - if off + len < 0, overflow occurred
        if (off < 0 || len < 0 || off + len > d.length || off + len < 0) {
            throw new IndexOutOfBoundsException
                ("off < 0 || len < 0 || off + len > d.length!");
        }

        while (len > 0) {
            int nelts = Math.min(len, byteBuf.length/8);
            readFully(byteBuf, 0, nelts*8);
            toDoubles(byteBuf, d, off, nelts);
            off += nelts;
            len -= nelts;
        }
    }

    private void toShorts(byte[] b, short[] s, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                s[off + j] = (short)((b0 << 8) | b1);
                boff += 2;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 1];
                int b1 = b[boff] & 0xff;
                s[off + j] = (short)((b0 << 8) | b1);
                boff += 2;
            }
        }
    }

    private void toChars(byte[] b, char[] c, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                c[off + j] = (char)((b0 << 8) | b1);
                boff += 2;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 1];
                int b1 = b[boff] & 0xff;
                c[off + j] = (char)((b0 << 8) | b1);
                boff += 2;
            }
        }
    }

    private void toInts(byte[] b, int[] i, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                int b2 = b[boff + 2] & 0xff;
                int b3 = b[boff + 3] & 0xff;
                i[off + j] = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                boff += 4;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 3];
                int b1 = b[boff + 2] & 0xff;
                int b2 = b[boff + 1] & 0xff;
                int b3 = b[boff] & 0xff;
                i[off + j] = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                boff += 4;
            }
        }
    }

    private void toLongs(byte[] b, long[] l, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                int b2 = b[boff + 2] & 0xff;
                int b3 = b[boff + 3] & 0xff;
                int b4 = b[boff + 4];
                int b5 = b[boff + 5] & 0xff;
                int b6 = b[boff + 6] & 0xff;
                int b7 = b[boff + 7] & 0xff;

                int i0 = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                int i1 = (b4 << 24) | (b5 << 16) | (b6 << 8) | b7;

                l[off + j] = ((long)i0 << 32) | (i1 & 0xffffffffL);
                boff += 8;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 7];
                int b1 = b[boff + 6] & 0xff;
                int b2 = b[boff + 5] & 0xff;
                int b3 = b[boff + 4] & 0xff;
                int b4 = b[boff + 3];
                int b5 = b[boff + 2] & 0xff;
                int b6 = b[boff + 1] & 0xff;
                int b7 = b[boff]     & 0xff;

                int i0 = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                int i1 = (b4 << 24) | (b5 << 16) | (b6 << 8) | b7;

                l[off + j] = ((long)i0 << 32) | (i1 & 0xffffffffL);
                boff += 8;
            }
        }
    }

    private void toFloats(byte[] b, float[] f, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                int b2 = b[boff + 2] & 0xff;
                int b3 = b[boff + 3] & 0xff;
                int i = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                f[off + j] = Float.intBitsToFloat(i);
                boff += 4;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 3];
                int b1 = b[boff + 2] & 0xff;
                int b2 = b[boff + 1] & 0xff;
                int b3 = b[boff + 0] & 0xff;
                int i = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                f[off + j] = Float.intBitsToFloat(i);
                boff += 4;
            }
        }
    }

    private void toDoubles(byte[] b, double[] d, int off, int len) {
        int boff = 0;
        if (byteOrder == ByteOrder.BIG_ENDIAN) {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff];
                int b1 = b[boff + 1] & 0xff;
                int b2 = b[boff + 2] & 0xff;
                int b3 = b[boff + 3] & 0xff;
                int b4 = b[boff + 4];
                int b5 = b[boff + 5] & 0xff;
                int b6 = b[boff + 6] & 0xff;
                int b7 = b[boff + 7] & 0xff;

                int i0 = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                int i1 = (b4 << 24) | (b5 << 16) | (b6 << 8) | b7;
                long l = ((long)i0 << 32) | (i1 & 0xffffffffL);

                d[off + j] = Double.longBitsToDouble(l);
                boff += 8;
            }
        } else {
            for (int j = 0; j < len; j++) {
                int b0 = b[boff + 7];
                int b1 = b[boff + 6] & 0xff;
                int b2 = b[boff + 5] & 0xff;
                int b3 = b[boff + 4] & 0xff;
                int b4 = b[boff + 3];
                int b5 = b[boff + 2] & 0xff;
                int b6 = b[boff + 1] & 0xff;
                int b7 = b[boff] & 0xff;

                int i0 = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
                int i1 = (b4 << 24) | (b5 << 16) | (b6 << 8) | b7;
                long l = ((long)i0 << 32) | (i1 & 0xffffffffL);

                d[off + j] = Double.longBitsToDouble(l);
                boff += 8;
            }
        }
    }

    public long getStreamPosition() throws IOException {
        checkClosed();
        return streamPos;
    }

    public int getBitOffset() throws IOException {
        checkClosed();
        return bitOffset;
    }

    public void setBitOffset(int bitOffset) throws IOException {
        checkClosed();
        if (bitOffset < 0 || bitOffset > 7) {
            throw new IllegalArgumentException("bitOffset must be betwwen 0 and 7!");
        }
        this.bitOffset = bitOffset;
    }

    public int readBit() throws IOException {
        checkClosed();

        // Compute final bit offset before we call read() and seek()
        int newBitOffset = (this.bitOffset + 1) & 0x7;

        int val = read();
        if (val == -1) {
            throw new EOFException();
        }

        if (newBitOffset != 0) {
            // Move byte position back if in the middle of a byte
            seek(getStreamPosition() - 1);
            // Shift the bit to be read to the rightmost position
            val >>= 8 - newBitOffset;
        }
        this.bitOffset = newBitOffset;

        return val & 0x1;
    }

    public long readBits(int numBits) throws IOException {
        checkClosed();

        if (numBits < 0 || numBits > 64) {
            throw new IllegalArgumentException();
        }
        if (numBits == 0) {
            return 0L;
        }

        // Have to read additional bits on the left equal to the bit offset
        int bitsToRead = numBits + bitOffset;

        // Compute final bit offset before we call read() and seek()
        int newBitOffset = (this.bitOffset + numBits) & 0x7;

        // Read a byte at a time, accumulate
        long accum = 0L;
        while (bitsToRead > 0) {
            int val = read();
            if (val == -1) {
                throw new EOFException();
            }

            accum <<= 8;
            accum |= val;
            bitsToRead -= 8;
        }

        // Move byte position back if in the middle of a byte
        if (newBitOffset != 0) {
            seek(getStreamPosition() - 1);
        }
        this.bitOffset = newBitOffset;

        // Shift away unwanted bits on the right.
        accum >>>= (-bitsToRead); // Negative of bitsToRead == extra bits read

        // Mask out unwanted bits on the left
        accum &= (-1L >>> (64 - numBits));

        return accum;
    }

    
Returns -1L to indicate that the stream has unknown
length.  Subclasses must override this method to provide actual
length information.

Returns:-1L to indicate unknown length.
/**
     * Returns <code>-1L</code> to indicate that the stream has unknown
     * length.  Subclasses must override this method to provide actual
     * length information.
     *
     * @return -1L to indicate unknown length.
     */
    public long length() {
        return -1L;
    }

    
Advances the current stream position by calling
seek(getStreamPosition() + n).

 The bit offset is reset to zero.

Params:
  • n – the number of bytes to seek forward.
Throws:
  • IOException – if getStreamPosition
throws an IOException when computing either
the starting or ending position.
Returns:an int representing the number of bytes
skipped.
/**
     * Advances the current stream position by calling
     * <code>seek(getStreamPosition() + n)</code>.
     *
     * <p> The bit offset is reset to zero.
     *
     * @param n the number of bytes to seek forward.
     *
     * @return an <code>int</code> representing the number of bytes
     * skipped.
     *
     * @exception IOException if <code>getStreamPosition</code>
     * throws an <code>IOException</code> when computing either
     * the starting or ending position.
     */
    public int skipBytes(int n) throws IOException {
        long pos = getStreamPosition();
        seek(pos + n);
        return (int)(getStreamPosition() - pos);
    }

    
Advances the current stream position by calling
seek(getStreamPosition() + n).

 The bit offset is reset to zero.

Params:
  • n – the number of bytes to seek forward.
Throws:
  • IOException – if getStreamPosition
throws an IOException when computing either
the starting or ending position.
Returns:a long representing the number of bytes
skipped.
/**
     * Advances the current stream position by calling
     * <code>seek(getStreamPosition() + n)</code>.
     *
     * <p> The bit offset is reset to zero.
     *
     * @param n the number of bytes to seek forward.
     *
     * @return a <code>long</code> representing the number of bytes
     * skipped.
     *
     * @exception IOException if <code>getStreamPosition</code>
     * throws an <code>IOException</code> when computing either
     * the starting or ending position.
     */
    public long skipBytes(long n) throws IOException {
        long pos = getStreamPosition();
        seek(pos + n);
        return getStreamPosition() - pos;
    }

    public void seek(long pos) throws IOException {
        checkClosed();

        // This test also covers pos < 0
        if (pos < flushedPos) {
            throw new IndexOutOfBoundsException("pos < flushedPos!");
        }

        this.streamPos = pos;
        this.bitOffset = 0;
    }

    
Pushes the current stream position onto a stack of marked
positions.

/**
     * Pushes the current stream position onto a stack of marked
     * positions.
     */
    public void mark() {
        try {
            markByteStack.push(new Long(getStreamPosition()));
            markBitStack.push(new Integer(getBitOffset()));
        } catch (IOException e) {
        }
    }

    
Resets the current stream byte and bit positions from the stack
of marked positions.

 An IOException will be thrown if the previous
marked position lies in the discarded portion of the stream.

Throws:
  • IOException – if an I/O error occurs.
/**
     * Resets the current stream byte and bit positions from the stack
     * of marked positions.
     *
     * <p> An <code>IOException</code> will be thrown if the previous
     * marked position lies in the discarded portion of the stream.
     *
     * @exception IOException if an I/O error occurs.
     */
    public void reset() throws IOException {
        if (markByteStack.empty()) {
            return;
        }

        long pos = ((Long)markByteStack.pop()).longValue();
        if (pos < flushedPos) {
            throw new IIOException
                ("Previous marked position has been discarded!");
        }
        seek(pos);

        int offset = ((Integer)markBitStack.pop()).intValue();
        setBitOffset(offset);
    }

    public void flushBefore(long pos) throws IOException {
        checkClosed();
        if (pos < flushedPos) {
            throw new IndexOutOfBoundsException("pos < flushedPos!");
        }
        if (pos > getStreamPosition()) {
            throw new IndexOutOfBoundsException("pos > getStreamPosition()!");
        }
        // Invariant: flushedPos >= 0
        flushedPos = pos;
    }

    public void flush() throws IOException {
        flushBefore(getStreamPosition());
    }

    public long getFlushedPosition() {
        return flushedPos;
    }

    
Default implementation returns false.  Subclasses should
override this if they cache data.

/**
     * Default implementation returns false.  Subclasses should
     * override this if they cache data.
     */
    public boolean isCached() {
        return false;
    }

    
Default implementation returns false.  Subclasses should
override this if they cache data in main memory.

/**
     * Default implementation returns false.  Subclasses should
     * override this if they cache data in main memory.
     */
    public boolean isCachedMemory() {
        return false;
    }

    
Default implementation returns false.  Subclasses should
override this if they cache data in a temporary file.

/**
     * Default implementation returns false.  Subclasses should
     * override this if they cache data in a temporary file.
     */
    public boolean isCachedFile() {
        return false;
    }

    public void close() throws IOException {
        checkClosed();

        isClosed = true;
    }

    
Finalizes this object prior to garbage collection.  The
close method is called to close any open input
source.  This method should not be called from application
code.

Throws:
  • Throwable – if an error occurs during superclass
finalization.
/**
     * Finalizes this object prior to garbage collection.  The
     * <code>close</code> method is called to close any open input
     * source.  This method should not be called from application
     * code.
     *
     * @exception Throwable if an error occurs during superclass
     * finalization.
     */
    protected void finalize() throws Throwable {
        if (!isClosed) {
            try {
                close();
            } catch (IOException e) {
            }
        }
        super.finalize();
    }
}