Back to index...

	/*
	* Copyright (c) 1994, 2006, 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 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.
	* <p>
	* DataInputStream is not necessarily safe for multithreaded access.
	* Thread safety is optional and is the responsibility of users of
	* methods in this class.
	*
	* @author Arthur van Hoff
	* @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>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 the first byte cannot be read for any reason
	* other than end of file, the stream has been closed and the underlying
	* input stream does not support reading after close, or another 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>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.
	*
	* @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 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 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 IOException if the first byte cannot be read for any reason
	* other than end of file, the stream has been closed and the underlying
	* input stream does not support reading after close, or another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the contained input stream does not support
	* seek, or the stream has been closed and
	* the contained input stream does not support
	* reading after close, or another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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, interpreted as a
	* <code>char</code>.
	* @exception EOFException if this input stream reaches the end before
	* reading two bytes.
	* @exception IOException the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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 the stream has been closed and the contained
	* input stream does not support reading after close, or
	* another 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);
	}
	}

Back to index...