/*
 * @(#)DataInputStream.java	1.71 04/05/28
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.io;

/**
 * A data input stream lets an application read primitive Java data
 * types from an underlying input stream in a machine-independent
 * way. An application uses a data output stream to write data that
 * can later be read by a data input stream.
 *
 * @author  Arthur van Hoff
 * @version 1.71, 05/28/04
 * @see     java.io.DataOutputStream
 * @since   JDK1.0
 */
public
class DataInputStream extends FilterInputStream implements DataInput {

    /**
     * Creates a DataInputStream that uses the specified
     * underlying InputStream.
     *
     * @param  in   the specified input stream
     */
    public DataInputStream(InputStream in) {
	super(in);
    }

    /**
     * working arrays initialized on demand by readUTF
     */
    private byte bytearr[] = new byte[80];
    private char chararr[] = new char[80];

    /**
     * Reads some number of bytes from the contained input stream and 
     * stores them into the buffer array <code>b</code>. The number of 
     * bytes actually read is returned as an integer. This method blocks 
     * until input data is available, end of file is detected, or an 
     * exception is thrown. 
     * 
     * <p>If <code>b</code> is null, a <code>NullPointerException</code> is 
     * thrown. If the length of <code>b</code> is zero, then no bytes are 
     * read and <code>0</code> is returned; otherwise, there is an attempt 
     * to read at least one byte. If no byte is available because the 
     * stream is at end of file, the value <code>-1</code> is returned;
     * otherwise, at least one byte is read and stored into <code>b</code>. 
     * 
     * <p>The first byte read is stored into element <code>b[0]</code>, the 
     * next one into <code>b[1]</code>, and so on. The number of bytes read 
     * is, at most, equal to the length of <code>b</code>. Let <code>k</code> 
     * be the number of bytes actually read; these bytes will be stored in 
     * elements <code>b[0]</code> through <code>b[k-1]</code>, leaving 
     * elements <code>b[k]</code> through <code>b[b.length-1]</code> 
     * unaffected. 
     * 
     * <p>If the first byte cannot be read for any reason other than end of 
     * file, then an <code>IOException</code> is thrown. In particular, an 
     * <code>IOException</code> is thrown if the input stream has been closed. 
     * 
     * <p>The <code>read(b)</code> method has the same effect as: 
     * <blockquote><pre>
     * read(b, 0, b.length) 
     * </pre></blockquote>
     *
     * @param      b   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end
     *             of the stream has been reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.InputStream#read(byte[], int, int)
     */
    public final int read(byte b[]) throws IOException {
	return in.read(b, 0, b.length);
    }

    /**
     * Reads up to <code>len</code> bytes of data from the contained 
     * input stream into an array of bytes.  An attempt is made to read 
     * as many as <code>len</code> bytes, but a smaller number may be read, 
     * possibly zero. The number of bytes actually read is returned as an 
     * integer.
     *
     * <p> This method blocks until input data is available, end of file is
     * detected, or an exception is thrown.
     *
     * <p> If <code>b</code> is <code>null</code>, a
     * <code>NullPointerException</code> is thrown.
     *
     * <p> If <code>off</code> is negative, or <code>len</code> is negative, or
     * <code>off+len</code> is greater than the length of the array
     * <code>b</code>, then an <code>IndexOutOfBoundsException</code> is
     * thrown.
     *
     * <p> If <code>len</code> is zero, then no bytes are read and
     * <code>0</code> is returned; otherwise, there is an attempt to read at
     * least one byte. If no byte is available because the stream is at end of
     * file, the value <code>-1</code> is returned; otherwise, at least one
     * byte is read and stored into <code>b</code>.
     *
     * <p> The first byte read is stored into element <code>b[off]</code>, the
     * next one into <code>b[off+1]</code>, and so on. The number of bytes read
     * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
     * bytes actually read; these bytes will be stored in elements
     * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
     * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
     * <code>b[off+len-1]</code> unaffected.
     *
     * <p> In every case, elements <code>b[0]</code> through
     * <code>b[off]</code> and elements <code>b[off+len]</code> through
     * <code>b[b.length-1]</code> are unaffected.
     *
     * <p> If the first byte cannot be read for any reason other than end of
     * file, then an <code>IOException</code> is thrown. In particular, an
     * <code>IOException</code> is thrown if the input stream has been closed.
     *
     * @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 total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end
     *             of the stream has been reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.InputStream#read(byte[], int, int)
     */
    public final int read(byte b[], int off, int len) throws IOException {
	return in.read(b, off, len);
    }

    /**
     * See the general contract of the <code>readFully</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      b   the buffer into which the data is read.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final void readFully(byte b[]) throws IOException {
	readFully(b, 0, b.length);
    }

    /**
     * See the general contract of the <code>readFully</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the number of bytes to read.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final void readFully(byte b[], int off, int len) throws IOException {
	if (len < 0)
	    throw new IndexOutOfBoundsException();
	int n = 0;
	while (n < len) {
	    int count = in.read(b, off + n, len - n);
	    if (count < 0)
		throw new EOFException();
	    n += count;
	}
    }

    /**
     * See the general contract of the <code>skipBytes</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int skipBytes(int n) throws IOException {
	int total = 0;
	int cur = 0;

	while ((total<n) && ((cur = (int) in.skip(n-total)) > 0)) {
	    total += cur;
	}

	return total;
    }

    /**
     * See the general contract of the <code>readBoolean</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the <code>boolean</code> value read.
     * @exception  EOFException  if this input stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final boolean readBoolean() throws IOException {
	int ch = in.read();
	if (ch < 0)
	    throw new EOFException();
	return (ch != 0);
    }

    /**
     * See the general contract of the <code>readByte</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream as a signed 8-bit
     *             <code>byte</code>.
     * @exception  EOFException  if this input stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final byte readByte() throws IOException {
	int ch = in.read();
	if (ch < 0)
	    throw new EOFException();
	return (byte)(ch);
    }

    /**
     * See the general contract of the <code>readUnsignedByte</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream, interpreted as an
     *             unsigned 8-bit number.
     * @exception  EOFException  if this input stream has reached the end.
     * @exception  IOException   if an I/O error occurs.
     * @see         java.io.FilterInputStream#in
     */
    public final int readUnsignedByte() throws IOException {
	int ch = in.read();
	if (ch < 0)
	    throw new EOFException();
	return ch;
    }

    /**
     * See the general contract of the <code>readShort</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as a
     *             signed 16-bit number.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final short readShort() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (short)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the <code>readUnsignedShort</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as an
     *             unsigned 16-bit integer.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final int readUnsignedShort() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (ch1 << 8) + (ch2 << 0);
    }

    /**
     * See the general contract of the <code>readChar</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream as a Unicode
     *             character.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final char readChar() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (char)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the <code>readInt</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as an
     *             <code>int</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final int readInt() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        int ch3 = in.read();
        int ch4 = in.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    private byte readBuffer[] = new byte[8];

    /**
     * See the general contract of the <code>readLong</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next eight bytes of this input stream, interpreted as a
     *             <code>long</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading eight bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final long readLong() throws IOException {
        readFully(readBuffer, 0, 8);
        return (((long)readBuffer[0] << 56) +
                ((long)(readBuffer[1] & 255) << 48) +
                ((long)(readBuffer[2] & 255) << 40) +
                ((long)(readBuffer[3] & 255) << 32) +
                ((long)(readBuffer[4] & 255) << 24) +
                ((readBuffer[5] & 255) << 16) +
                ((readBuffer[6] & 255) <<  8) +
                ((readBuffer[7] & 255) <<  0));
    }

    /**
     * See the general contract of the <code>readFloat</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as a
     *             <code>float</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.DataInputStream#readInt()
     * @see        java.lang.Float#intBitsToFloat(int)
     */
    public final float readFloat() throws IOException {
	return Float.intBitsToFloat(readInt());
    }

    /**
     * See the general contract of the <code>readDouble</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next eight bytes of this input stream, interpreted as a
     *             <code>double</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading eight bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.DataInputStream#readLong()
     * @see        java.lang.Double#longBitsToDouble(long)
     */
    public final double readDouble() throws IOException {
	return Double.longBitsToDouble(readLong());
    }

    private char lineBuffer[];

    /**
     * See the general contract of the <code>readLine</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @deprecated This method does not properly convert bytes to characters.
     * As of JDK 1.1, the preferred way to read lines of text is via the
     * <code>BufferedReader.readLine()</code> method.  Programs that use the
     * <code>DataInputStream</code> class to read lines can be converted to use
     * the <code>BufferedReader</code> class by replacing code of the form:
     * <blockquote><pre>
     *     DataInputStream d = new DataInputStream(in);
     * </pre></blockquote>
     * with:
     * <blockquote><pre>
     *     BufferedReader d
     *          = new BufferedReader(new InputStreamReader(in));
     * </pre></blockquote>
     *
     * @return     the next line of text from this input stream.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.BufferedReader#readLine()
     * @see        java.io.FilterInputStream#in
     */
    @Deprecated
    public final String readLine() throws IOException {
	char buf[] = lineBuffer;

	if (buf == null) {
	    buf = lineBuffer = new char[128];
	}

	int room = buf.length;
	int offset = 0;
	int c;

loop:	while (true) {
	    switch (c = in.read()) {
	      case -1:
	      case '\n':
		break loop;

	      case '\r':
		int c2 = in.read();
		if ((c2 != '\n') && (c2 != -1)) {
		    if (!(in instanceof PushbackInputStream)) {
			this.in = new PushbackInputStream(in);
		    }
		    ((PushbackInputStream)in).unread(c2);
		}
		break loop;

	      default:
		if (--room < 0) {
		    buf = new char[offset + 128];
		    room = buf.length - offset - 1;
		    System.arraycopy(lineBuffer, 0, buf, 0, offset);
		    lineBuffer = buf;
		}
		buf[offset++] = (char) c;
		break;
	    }
	}
	if ((c == -1) && (offset == 0)) {
	    return null;
	}
	return String.copyValueOf(buf, 0, offset);
    }

    /**
     * See the general contract of the <code>readUTF</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     a Unicode string.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @exception  IOException   if an I/O error occurs.
     * @exception  UTFDataFormatException if the bytes do not represent a valid
     *             modified UTF-8 encoding of a string.
     * @see        java.io.DataInputStream#readUTF(java.io.DataInput)
     */
    public final String readUTF() throws IOException {
        return readUTF(this);
    }

    /**
     * Reads from the
     * stream <code>in</code> a representation
     * of a Unicode  character string encoded in
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> format;
     * this string of characters is then returned as a <code>String</code>.
     * The details of the modified UTF-8 representation
     * are  exactly the same as for the <code>readUTF</code>
     * method of <code>DataInput</code>.
     *
     * @param      in   a data input stream.
     * @return     a Unicode string.
     * @exception  EOFException            if the input stream reaches the end
     *               before all the bytes.
     * @exception  IOException             if an I/O error occurs.
     * @exception  UTFDataFormatException  if the bytes do not represent a
     *               valid modified UTF-8 encoding of a Unicode string.
     * @see        java.io.DataInputStream#readUnsignedShort()
     */
    public final static String readUTF(DataInput in) throws IOException {
        int utflen = in.readUnsignedShort();
        byte[] bytearr = null;
        char[] chararr = null;
        if (in instanceof DataInputStream) {
            DataInputStream dis = (DataInputStream)in;
            if (dis.bytearr.length < utflen){
                dis.bytearr = new byte[utflen*2];
                dis.chararr = new char[utflen*2];
            }
            chararr = dis.chararr;
            bytearr = dis.bytearr;
        } else {
            bytearr = new byte[utflen];
            chararr = new char[utflen];
        }

        int c, char2, char3;
        int count = 0;
        int chararr_count=0;

        in.readFully(bytearr, 0, utflen);

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;      
            if (c > 127) break;
            count++;
            chararr[chararr_count++]=(char)c;
        }

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;
            switch (c >> 4) {
                case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                    /* 0xxxxxxx*/
                    count++;
                    chararr[chararr_count++]=(char)c;
                    break;
                case 12: case 13:
                    /* 110x xxxx   10xx xxxx*/
                    count += 2;
                    if (count > utflen)
                        throw new UTFDataFormatException(
                            "malformed input: partial character at end");
                    char2 = (int) bytearr[count-1];
                    if ((char2 & 0xC0) != 0x80)
                        throw new UTFDataFormatException(
                            "malformed input around byte " + count); 
                    chararr[chararr_count++]=(char)(((c & 0x1F) << 6) | 
                                                    (char2 & 0x3F));  
                    break;
                case 14:
                    /* 1110 xxxx  10xx xxxx  10xx xxxx */
                    count += 3;
                    if (count > utflen)
                        throw new UTFDataFormatException(
                            "malformed input: partial character at end");
                    char2 = (int) bytearr[count-2];
                    char3 = (int) bytearr[count-1];
                    if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
                        throw new UTFDataFormatException(
                            "malformed input around byte " + (count-1));
                    chararr[chararr_count++]=(char)(((c     & 0x0F) << 12) |
                                                    ((char2 & 0x3F) << 6)  |
                                                    ((char3 & 0x3F) << 0));
                    break;
                default:
                    /* 10xx xxxx,  1111 xxxx */
                    throw new UTFDataFormatException(
                        "malformed input around byte " + count);
            }
        }
        // The number of chars produced may be less than utflen
        return new String(chararr, 0, chararr_count);
    }
}